System Coupling Users Guide

System Coupling User's Guide

Release 15.0ANSYS, Inc.

November 2013Southpointe

275 Technology Drive

Canonsburg, PA 15317 ANSYS, Inc. is

certified to ISO

9001:[email protected]

http://www.ansys.com

(T) 724-746-3304

(F) 724-514-9494

Copyright and Trademark Information

© 2013 SAS IP, Inc. All rights reserved. Unauthorized use, distribution or duplication is prohibited.

ANSYS, ANSYS Workbench, Ansoft, AUTODYN, EKM, Engineering Knowledge Manager, CFX, FLUENT, HFSS and any

and all ANSYS, Inc. brand, product, service and feature names, logos and slogans are registered trademarks or

trademarks of ANSYS, Inc. or its subsidiaries in the United States or other countries. ICEM CFD is a trademark used

by ANSYS, Inc. under license. CFX is a trademark of Sony Corporation in Japan. All other brand, product, service

and feature names or trademarks are the property of their respective owners.

Disclaimer Notice

THIS ANSYS SOFTWARE PRODUCT AND PROGRAM DOCUMENTATION INCLUDE TRADE SECRETS AND ARE CONFID-

ENTIAL AND PROPRIETARY PRODUCTS OF ANSYS, INC., ITS SUBSIDIARIES, OR LICENSORS. The software products

and documentation are furnished by ANSYS, Inc., its subsidiaries, or affiliates under a software license agreement

that contains provisions concerning non-disclosure, copying, length and nature of use, compliance with exporting

laws, warranties, disclaimers, limitations of liability, and remedies, and other provisions. The software products

and documentation may be used, disclosed, transferred, or copied only in accordance with the terms and conditions

of that software license agreement.

ANSYS, Inc. is certified to ISO 9001:2008.

U.S. Government Rights

For U.S. Government users, except as specifically granted by the ANSYS, Inc. software license agreement, the use,

duplication, or disclosure by the United States Government is subject to restrictions stated in the ANSYS, Inc.

software license agreement and FAR 12.212 (for non-DOD licenses).

Third-Party Software

See the legal information in the product help files for the complete Legal Notice for ANSYS proprietary software

and third-party software. If you are unable to access the Legal Notice, please contact ANSYS, Inc.

Published in the U.S.A.

Table of Contents

About This Manual ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Document Conventions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Technical Support ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

System Coupling Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Supported System Couplings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Product Licensing Considerations when using System Coupling .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

System Coupling Workspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Setting Up a Simulation that Uses System Coupling .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Components of the System Coupling Workspace .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Outline View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Properties View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Chart Monitor View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Solution Information View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Settings for Completing a System Coupling Setup .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Analysis Settings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Analysis Type .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Initialization Controls ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Coupling Initialization .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Duration Controls ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Duration Defined By .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Step Controls ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Analysis Settings Best Practices .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

General Analysis Type .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Transient Analysis Type .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Participants .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Working with Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Data Transfer Rules .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Execution Control ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Co-Simulation Participant Sequencing .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Sequential Solutions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Simultaneous Solutions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Debug Output Control ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Intermediate Restart Data Output .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Validation and State of the System Coupling Setup Cell .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

System Coupling Setup Cell Context Menus .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Expert Settings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Settings for Running a System Coupling Solution .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Solution Information .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Chart Monitors ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Chart Properties ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Chart Variable .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Chart Variable Properties ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Working with Convergence Charts ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Using the Scene Chart Monitor View .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Validation and State of the System Coupling Solution Cell .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

System Coupling Solution Cell Context Menus .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Workflows for System Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Executing System Couplings Using the Command Line .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

System Coupling Command Line Options .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

iiiRelease 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

of ANSYS, Inc. and its subsidiaries and affiliates.

Restarting a System Coupling Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Generating Restart Files ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Executing the Restart Run .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Recovering from a Workbench Crash .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Stopping the Coupled Analysis Run .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Understanding the System Coupling Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Coupling Management .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Inter-Process Communication .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Process Synchronization and Analysis Evolution .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Convergence Management .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Evaluating Convergence of Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Data Pre-Processing Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Creating Nodal Data from Face/Element Centroid Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Creating Face/Element Data from Node Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Mapping Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Data Transfer Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Profile Preserving .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Conservative Profile Preserving .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Bucket Surface .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

General Grid Interface (GGI) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Interpolation Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Interpolated Data Post-Processing Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Ramping Algorithm ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Under-Relaxation Algorithm ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Initial Values used in Ramping and Under-Relaxation Algorithms .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Clipping Algorithm ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Files Used by the Coupling Service .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

System Coupling Service Input File (scInput.sci ) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

System Coupling Service Shutdown File (scStop.stop ) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Files Generated by Coupling Service .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

System Coupling Server File (scServer.scs ) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

System Coupling Service Log File (scLog.scl_, scLog_##.scl ) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

System Coupling Results File (scResults_##_######.scr ) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Understanding the System Coupling Input File ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Understanding the System Coupling Log File ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Best Practice Guidelines for Using System Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Building up a Coupled Analysis from Decoupled Systems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Troubleshooting Two-Way Coupled Analyses Problems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Using Text-Based Monitor Output to Debug Coupled Analyses .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Using Graphical Monitor Output to Debug Coupled Analyses .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Using Supplemental Output to Debug Coupled Analyses .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Supplemental Output for Diagnosing Mapping Problems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Improving Coupled Analysis Stability ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Data Transfer Ramping .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Participant Solution Stabilization .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Co-Simulation Participants Sequencing ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Controlling Participant Sequencing .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Using Sequencing to Reduce Coupled Solution Execution Time .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Tutorial: Oscillating Plate with Two-Way Fluid-Structure Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Overview of the Problem to Solve .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

Creating the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationof ANSYS, Inc. and its subsidiaries and affiliates.iv


Optional: Preparing for a Command-line Run .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Adding Analysis Systems to the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Adding a New Material for the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Adding Geometry to the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Defining the Physics in the Mechanical Application .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Generating the Mesh for the Structural System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Assigning the Material to the Geometry .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Setting the Basic Analysis Values .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Inserting Loads .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Defining the Fixed Support ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Defining the Fluid-Solid Interface .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Defining the Pressure Load .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Preparing for a Command-Line Run of the Structural System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Completing the Setup for the Structural System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Setting up your Fluid Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Generating the Mesh for the Fluid System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Defining the Physics in the ANSYS Fluent Application .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Adding the Solution Setup Settings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Defining the Dynamic Mesh .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Adding the Solution Settings .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Preparing for a Command-Line Run of the Fluent System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Defining and Running the Coupling in the System Coupling Application .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Setting the Basic Analysis Values .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Creating the Data Transfers ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Preparing System Coupling for Restarts ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Solving and Restarting the Coupled Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Preparing for a Command-Line Run of the System Coupling System ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Viewing Results in CFD-Post ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Creating an Animation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Plotting Results on the Solid .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Post-Processing in Mechanical ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Setting Up and Executing a Coupled Analysis Restart from Workbench .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Executing the Coupled Analysis from the Command Line .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Preparing the Required Input Files ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Running the Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Restart Analysis Execution .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Preparing the Required Input Files ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Run the Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Loading the Results into CFD-Post ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Tutorial: Heat Transfer from a Heating Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Overview of the Problem to Solve .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Part 1: Transferring Data from the Steady-State Thermal Analysis to the Fluid Flow Analysis ... . . . . . . . . . . . . . . . 112

Creating the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Setting the Units in ANSYS Workbench .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Adding Analysis and Component Systems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Adding New Materials for the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Adding Geometry to the Project ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Preparing the Steady-State Thermal Source Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Assigning the Material to the Geometry .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Generating the Mesh .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Defining the Physics for the Structural Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Defining the Steady-State Thermal Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

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Executing the Structural Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Post-Processing the Structural Analysis Results ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Using External Data to Access the Steady-State Thermal Source Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Preparing the Fluid Flow Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Importing the Mesh for the Fluid Flow Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Defining the Physics for the Fluid Flow Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Preparing and Executing the Coupled Thermal Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Reviewing Results in CFD-Post ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Part 2: Transferring Data from the Fluid Flow Analysis to the Steady-State Thermal Analysis ... . . . . . . . . . . . . . . . 126

Exporting the Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Adding Additional Analysis and Component Systems .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Using External Data to Access the Fluid Flow Source Data ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Preparing the Steady-State Thermal Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Preparing and Executing the Coupled Thermal Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Reviewing Results in the Mechanical Application .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Index .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

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About This Manual

This manual describes how to use the System Coupling component to control otherwise independent

physics solvers or external data sources so that they work together in a coupled analysis such as Fluid-

Structure Interaction (FSI).

This manual contains the following chapters:

• "System Coupling Overview" (p. 1) describes how System Coupling works and the types of simulations

you can perform.

• "System Coupling Workspace" (p. 7) describes how to use the System Coupling views in ANSYS Workbench

to control the analysis.

• "Workflows for System Coupling" (p. 33) describes common workflow topics such as using the command

line, and restarting coupled analyses

• "Understanding the System Coupling Service" (p. 41) describes files used by the Coupling Service, the

communication technology, the run time environment, and the mapping technologies.

• "Best Practice Guidelines for Using System Coupling" (p. 73) describes best practices for using System

Coupling.

• "Tutorial: Oscillating Plate with Two-Way Fluid-Structure Interaction" (p. 79) guides you through performing

an example of a coupled analysis.

• "Tutorial: Heat Transfer from a Heating Coil" (p. 111) demonstrates how to execute a sequence of one-way

thermal transfers in a heat exchanger using System Coupling.

Document Conventions

This section describes the conventions used in this document to distinguish between text, file names,

system messages, and input that you need to type.

File and Directory Names

File names and directory names appear in this font: /usr/lib .

User Input

Input you must type exactly is shown like this:

cd /usr

Input Substitution

Input that you must supply in a command is shown like this:

fluent 3d -schost="HostName"

That is, you should actually type fluent 3d -schost=" " and substitute a computer's name

for HostName.

Optional Arguments

Optional arguments are shown using square brackets:

export -cgns [-verbose] file

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Here the argument -verbose is optional, but you must specify a suitable file name.

Technical Support

Technical Support for ANSYS, Inc. products is provided either by ANSYS, Inc. directly or by one of our

certified ANSYS Support Providers. Please check with the ANSYS Support Coordinator (ASC) at your

company to determine who provides support for your company, or go to www.ansys.com and select

Contact ANSYS > Contacts and Locations.

If your support is provided by ANSYS, Inc. directly, Technical Support can be accessed quickly and effi-

ciently from the ANSYS Customer Portal, which is available from the ANSYS Website (www.ansys.com)

under Support > Customer Portal. The direct URL is: support.ansys.com.

One of the many useful features of the Customer Portal is the Knowledge Resources Search, which can

be found on the Home page of the Customer Portal.

Systems and installation Knowledge Resources are easily accessible via the Customer Portal by using

the following keywords in the search box: Systems/Installation . These Knowledge Resources

provide solutions and guidance on how to resolve installation and licensing issues quickly.

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Toll-Free Telephone: 1.800.711.7199

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Support for University customers is provided only through the ANSYS Customer Portal.

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About This Manual

http://www.ansys.com/

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Telephone: Please have your Customer or Contact ID ready.

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About This Manual






System Coupling Overview

The ANSYS suite of analysis software facilitates creation of a spectrum of single- and multidisciplinary

simulations. Multidisciplinary simulations are offered within the context of a single piece of software

(for example, within one solver) and using various dedicated mechanisms to couple a single piece of

software with others. Examples of the latter include mechanisms to import external data from static

sources, and the Multi-Field External (MFX) solver used for co-simulation between ANSYS Mechanical

MAPDL and ANSYS CFX. These coupling mechanisms provide optimal solutions for the analyses that

follow the single, specific workflow that they were built to solve.

The System Coupling infrastructure discussed in this manual should be considered for generic workflows

involving any number of analysis types, static data source and co-simulation participants, and data

transfer quantities and directions. The Workbench System Coupling component system is an easy-to-

use, all-purpose infrastructure that facilitates comprehensive multidisciplinary simulations between

coupling participants.

Coupling participants are systems that will provide and/or consume data in a coupled analysis. Example

systems in Workbench include:

• Analysis Systems – Steady-State Thermal, Transient Thermal, Static Structural, Transient Structural, Fluid

Flow (Fluent)

• Component Systems – Fluent, External Data

The execution of analyses involving couplings between any of these participants is managed by the

System Coupling Service, which is the runtime component of the System Coupling system. During exe-

cution, a variety of one- and two-way data transfers are performed between coupling participants. For

example, when multiple participants are executing their parts of a coupled analysis together, which is

often referred to as co-simulation, they may engage in both one- and two-way data transfers as either

a source or target. Similarly, when participants are providing access to existing results or data, which

shall be referred to as a static data source, they may engage in only one-way data transfers as a source.

This documentation provides a detailed description of capabilities supported by the System Coupling

component system. All of these capabilities may, however, not yet be supported in conjunction with

other Workbench systems. For information about systems that may act as participants in system couplings,

see the summary of Supported System Couplings (p. 3).

For information regarding product licensing details and interactions with System Couplings, see Product

Licensing Considerations when using System Coupling (p. 4).

To set up and execute a system coupling simulation, perform the following steps:

1. Create the project.

2. Add the individual, participant systems to the project.

3. Add the System Coupling system to the project.

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4. Set up each individual, participating system (generally from top-to-bottom, until you have completed

all the required steps for your analysis).

5. Connect the systems together as shown in Figure 1: Example of Connecting a System Coupling Com-

ponent System with Various Types of Systems (p. 2). For co-simulation participants and the External

Data static data participant, connections are drawn from the participants’ Setup cells.

6. Set up the System Coupling system (see "System Coupling Workspace" (p. 7)).

Figure 1: Example of Connecting a System Coupling Component System with Various Types of

Systems

It is important to note that updates of co-simulation participant (for example, a solver) Solution cells

are disabled for Workbench systems connected to the System Coupling system; these updates (and

execution of the respective solvers) are automatically initiated when the System Coupling Solution cell

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is updated. Note, however, that these updates respect all settings (for example parallel, precision, and

so on) already made for them.

Important

Using System Coupling in conjunction with the Remote Solver Manager (RSM) is not supported.

In the isolated case of Mechanical, the use of RSM for runs on a single local host is, however,

permitted.

After you have updated the System Coupling Solution cell, you can:

• Pause the analysis by interrupting its progress.

• Restart the analysis as described in the Initialization Controls (p. 10).

• Debug your system coupling simulation by using the system coupling command line arguments (see

System Coupling Command Line Options (p. 34)). You can also perform additional debugging of the

connected systems as described in Troubleshooting Two-Way Coupled Analyses Problems (p. 73).

• Use CFD-Post to simultaneously analyze the results of the simulation by:

– Connecting other participant systems’ Solution cells to the Results cell of the Fluid Flow system, or

– Connecting all participant systems’ Solution cells to a Results component system that you introduce in

the schematic.

Supported System Couplings

The following is the list of supported coupling participants:

• Fluent

• Static Structural

• Transient Structural

• Steady-State Thermal

• Transient Thermal

• External Data

Fluent can be connected with any of the other supported participants. In addition, the Steady-State

Thermal system can be connected with external data. Note that Steady-State and Static systems cannot

be coupled with Transient systems.

Note

Only two coupling participants can be connected to the System Coupling system at one

time. However, more than one System Coupling system may be introduced within the same

project schematic.



Supported System Couplings

For information about using System Coupling with the ANSYS Fluent system in Workbench, see Perform-

ing System Coupling Simulations Using Fluent in Workbench in the Fluent in Workbench User's Guide.

For information about restarting a coupled analysis with Fluent, see Restarting Fluent Analyses as Part

of System Couplings.

For information about using System Coupling with the ANSYS Mechanical system in Workbench, see

System Coupling in the ANSYS Mechanical User's Guide. For information about restarting a coupled

analysis with Mechanical, see Restarting Structural Mechanical Analyses as Part of System Coupling.

For information about using System Coupling with the External Data system in Workbench, see External

Data.

Product Licensing Considerations when using System Coupling

The licenses needed for System Coupling analyses are listed in Table 1: Licenses Required for Participating

Systems in System Coupling (p. 4). No additional licenses are required for the System Coupling infra-

structure.

The simultaneous execution of coupling participants currently precludes the use of the license sharing

feature that exists for some product licenses. The following specific requirements consequently exist:

• Distinct licenses are required for each coupling participant.

• Licensing preferences should be set to ‘Use a separate license for each application’ rather than ‘Share

a single license between applications when possible.’

The requirements listed above are particularly relevant for ANSYS Academic products.

Table 1: Licenses Required for Participating Systems in System Coupling

Academic License RequiredCommercial License Re-

quired

System

Fluent • ANSYS Academic Associate,• ANSYS CFD,

• ANSYS Fluent, or • ANSYS Academic Associate CFD,

• ANSYS Academic Research,• ANSYS Fluent Solver

• ANSYS Academic Research CFD,

• ANSYS Academic Teaching Ad-

vanced,

• ANSYS Academic Teaching Intro-

ductory, or

• ANSYS Academic Teaching CFD

Static Struc-

tural or

• ANSYS Academic Associate,• ANSYS Structural,

• •ANSYS Mechanical, ANSYS Academic Research,Transient

Structural•• ANSYS Academic Research Mech-

anical,

ANSYS Mechanical CFD-Flo,

• ANSYS Mechanical Emag,



Academic License RequiredCommercial License Re-

quired

System


vanced,

• ANSYS Multiphysics,

• ANSYS Structural Solver,

• ANSYS Academic Teaching Intro-

ductory, or• ANSYS Mechanical Solver,

or

• ANSYS Academic Teaching

Mechanical• ANSYS Multiphysics Solver

Steady-State

Thermal or

• ANSYS Academic Associate,• ANSYS Mechanical,

• •ANSYS Mechanical CFD-Flo, ANSYS Academic Research,Transient

Thermal•• ANSYS Academic Research Mech-

anical,

ANSYS Mechanical Emag,

• ANSYS Multiphysics,


vanced,• ANSYS Structural Solver,

• ANSYS Mechanical Solver,

or• ANSYS Academic Teaching Intro-

ductory, or

• ANSYS Multiphysics Solver • ANSYS Academic Teaching

Mechanical

No license is needed to run External Data.External

Data



Product Licensing Considerations when using System Coupling

System Coupling Workspace

This chapter discusses the following topics:

Setting Up a Simulation that Uses System Coupling

Components of the System Coupling Workspace

Settings for Completing a System Coupling Setup

Settings for Running a System Coupling Solution

Setting Up a Simulation that Uses System Coupling

The general workflow for setting up a System Coupling simulation is presented in "System Coupling

Overview" (p. 1).

Most participant systems with connections originating from their Setup cells will participate in the

analysis in a co-simulation mode (visually indicated in the Project Schematic with connections between

the Setup cells, and different icons and colors for the Solution cells). The exception to this is the External

Data participant system, since a connection originates from its Setup cell, but it acts as a static data

participant. The Update option is disabled from within the right-click menu of the co-simulation parti-

cipant systems' Solution cells because the update (and solution execution) is now controlled by the

System Coupling Solution cell.

Note that using System Coupling in conjunction with the Remote Solver Manager (RSM) is not supported

for runs on multiple host machines. In the isolated case of Mechanical, the use of RSM for runs on a

single local host is, however, permitted.

The System Coupling system in the Project Schematic has two cells:

• Setup: Use this cell to see participant, region, and variable information, and to define analysis settings

and data transfer between participants. Double-click the Setup cell, or right-click and choose Edit from

the context menu to display the System Coupling workspace.

• Solution: Use this cell to solve a coupled analysis and to see solution information and data convergence

plots or chart monitors. Double-click the Solution cell, or right-click and choose Edit from the context

menu to display the System Coupling workspace.

Components of the System Coupling Workspace

When you edit the Setup or Solution cells of the System Coupling component system, the same System

Coupling workspace is displayed in a tab within your workbench project. The Outline view, Properties

view, Chart Monitor view, and Solution Information view are displayed by default. For more information

about the tabbed views in Workbench, see Workbench Tabs and Views in the Workbench User's Guide.



Figure 2: The System Coupling Workspace

See the following sections for additional information:

Outline View

Properties View

Chart Monitor View

Solution Information View

Outline View

The Outline view (in the upper left corner of Figure 2: The System Coupling Workspace (p. 8)) presents

various fields related to the coupling participants and to the setup and solution of the coupled systems.

The deepest fields can be edited in the Properties view. For additional information, see Settings for

Completing a System Coupling Setup (p. 9) and Settings for Running a System Coupling Solution (p. 28).

Properties View

The Properties view (in the lower left corner of Figure 2: The System Coupling Workspace (p. 8))

presents the properties of an editable item selected in the Outline view. For additional information,



see Settings for Completing a System Coupling Setup (p. 9) and Settings for Running a System

Coupling Solution (p. 28).

Chart Monitor View

The Chart Monitor view (in the upper right corner of Figure 2: The System Coupling Workspace (p. 8))

presents convergence plots and chart monitors in the System Coupling workspace during the solution

process. For additional information, see Chart Monitors (p. 29) and Using the Scene Chart Monitor

View (p. 31).

Solution Information View

The Solution Information view (in the lower right corner of Figure 2: The System Coupling Work-

space (p. 8)) presents a text-based solution log of information output during the execution of the

coupled analysis. For additional information, see Solution Information (p. 28).


This section describes:

• All the settings that appear in the Outline and Properties views under the “Setup” branch.

• Context menus (that is, the menus that appear with a right-click) for the Setup cell.


Analysis Settings

Participants

Data Transfers

Data Transfer Rules

Execution Control

Validation and State of the System Coupling Setup Cell

System Coupling Setup Cell Context Menus

Expert Settings

Analysis Settings

The Analysis Settings field has the following properties:

• Analysis Type

• Initialization Controls

• Duration Controls

• Step Controls

Suggested best practices for analysis settings are discussed in Analysis Settings Best Practices (p. 12).

Analysis Type

This option is used to define the overall coupling type for the analysis.

The available options are:




• General

– This is the only available option when one or more of the coupling participants is executing steady or

static analyses. Note that mixed steady/static and transient analyses are not currently possible.

• Transient

– This is the only available option when all of the coupling participants are executing transient analyses.

Initialization Controls

This option is used to define the initialization controls available for all coupling types.

Coupling Initialization


• Program Controlled

– For initial runs (that is, not restart runs), the initial time and step are each set to 0.

– For restart runs, the initial time and step are set to the values obtained from the latest valid restart

point.

• Restart Points (indicated by Step and Time)

– The system coupling simulation can have multiple restart points when Intermediate Restart Data Out-

put (p. 22) is selected for either all coupling steps or for a set of coupling step intervals. The next

coupled analysis will be started based on the restart point that you have selected.

For more information regarding restarts, see Restarting a System Coupling Analysis (p. 35).

Important

Program controlled or explicitly specified restart points only affect the coupling step

and/or time used to restart the coupling service. Appropriate restart points must also

be specified for the co-simulation participants that are part of the coupled analysis. For

more information about coupling participants, see Restarting a System Coupling Analysis.

Duration Controls

This option is used to define the duration for the analysis.

Duration Defined By

The options available to define the duration of a coupled analysis are:

• End Time

– Available only when the Analysis Type is Transient

– When the End Time option is used, the coupling service will execute coupling steps until the specified

end time is reached. In a transient analysis, each coupling step is a time step (with the time interval



specified by the step size). Note that the final coupling step size is reduced automatically, if needed,

so that the specified end time is respected.

– Some of the participant systems, such as ANSYS Mechanical, require the end time specified in their

setup to be respected. When a coupled analysis involves one or more participants that require their

setup’s end time be respected, then the maximum allowable end time for the coupled analysis is the

minimum of the end times reported by such participants. In this case, a validation error will be reported

if the coupled analysis’ specified end time is greater than the minimum identified.

Other participant systems, such as Fluent, can run past the end time specified. These participant

systems have no effect on the allowable end time of the coupled analysis.

• Number of Steps

– Available only when the Analysis Type is General.

– When this option is used, the coupling service will execute coupling steps until the specified number

of steps is reached.

Step Controls

The duration of the coupled analysis is broken into a sequence of coupling steps. Data transfers between

the coupled solvers occur at the beginning of each coupling iteration within a coupling step. Coupling

steps are always indexed. During the analysis, each new coupling step is started when:

• The coupling analysis duration has not been reached, and

• Either the maximum number of coupling iterations has been reached or the coupling step is converged.


• Step Size

– If the coupling is defined in terms of time (a transient analysis), then a coupling step is associated with

a time interval. The Step Size option specifies the time interval associated with each coupling step (in

seconds). The final coupling step size is reduced automatically, if needed, so that the specified end time

is respected. This reduction does not occur if the analysis duration is set by the Number of Steps.

– The coupling step size is fixed for the duration of the System Coupling analysis, but it can be changed

when restarting the analysis.

• Minimum Iterations

– This option allows specification of the fewest number of coupling iterations (at least 1) that could be

executed per coupling step.

– The specified minimum number of coupling iterations will be executed even if all measures of conver-

gence are realized in fewer iterations.

• Maximum Iterations

– This option allows specification of the greatest number of coupling iterations that could possibly be

executed per coupling step.




– The specified maximum number of coupling iterations may not be executed if the analysis converges

prior to the maximum iteration step being reached.

Analysis Settings Best Practices

This section provides information about best practices for the following analysis settings:

General Analysis Type

Transient Analysis Type

General Analysis Type

With a General analysis type, accurate coupled solutions can be achieved using different combinations

of coupling step and coupling iteration specifications. The two cases described below are: when an

analysis is solved using one coupling step, and when an analysis is solved using many coupling steps.

Your choice of the combination of coupling steps and coupling iterations will:

• determine when result and/or restart data is able to be written, as the restart points can only be

written at the end of a coupling step,

• allow you to balance the required file storage space and your need for analysis restarts,

• determine how you can use system coupling’s under-relaxation factor (see Under-Relaxation Al-

gorithm (p. 54)) and ramping (see Ramping Algorithm (p. 53)), as these only apply to coupling itera-

tions and cannot be applied over coupling steps.

For more information about restarting your coupled analysis, see Restarting a System Coupling Analys-

is (p. 35).

Coupled Analysis solved using only one Coupling Step

A coupled analysis can be solved using only one coupling step. In this case, the coupling step is made

up of many coupling iterations, and the solution is complete at the end of this one step. The analysis

will continue executing until either the solution converges, or the specified maximum number of

coupling iterations is completed. Only the end of a coupling step can be used as a restart point. When

only one coupling step is used, results and restart data is generated only at the end of the solution.

The analysis can be terminated as usual, but because intermediate restart data is not generated, the

coupled analysis cannot be restarted if it terminates abnormally (due to an error, power interruption,

etc.) or if you terminate it before the coupling step is completed. Using only one coupling step within

a coupled analysis minimizes file storage space at the expense of the ability to restart the analysis. In-

terrupting the analysis will not affect the analysis, because System Coupling will complete the current

coupling step (and so complete the solution) before stopping the analysis. Ramping and under-relaxation

can be applied across coupling iterations within the single coupling step.

Coupled Analysis solved using many Coupling Steps

A coupled analysis can be solved using many coupling steps. In this case, the coupling steps are made

up of one or more coupling iterations. The analysis will continue executing until the specified number

of coupling steps is completed. The transition from one coupling step to the next will occur when either

the solution converges or the specified maximum number of coupling iterations is completed. Only the

end of a coupling step can be used as a restart point (you are able to specify which steps are used).

Results and restart data is generated at the specified restart points. If the analysis should terminate

abnormally within a coupling step, you can restart the analysis from the previous restart point. By using

more coupling steps with fewer coupling iterations per step, as opposed to one coupling step with

many coupling iterations, more points at which restarts can be done are created. For difficult or complex



analyses, which might experience abnormal terminations, more restart points allow restarts of the

analysis (saving time and computational effort) at the expense of file storage space. System Coupling’s

ramping and under-relaxation can be used across coupling iterations, but cannot be used across

coupling steps, so System Coupling always transfers the full data transfer value at the end of each

coupling step. Participant solvers may ramp data received from System Coupling at the coupling steps.

Transient Analysis Type

In a transient analysis, a coupling step is associated with a time interval by specifying the coupling step

size (in seconds). With a time specified, a coupling step is the same as a time step within the transient

analysis. The coupling step size used should reflect the time scales of the physics being studied. Note

that unless sub-stepping is supported by the co-simulation participants being coupled, the coupling

step size will typically be limited by the finest/smallest time scale of the co-simulation participants. If

the analysis duration is specified using an End Time, then care should be taken to ensure that an integral

number of coupling steps can be executed between the (re)start time and the specified end time. If

this is not done, then the final coupling step size will be reduced to respect the specified end time, and

this may introduce temporal discretization error into the coupled analysis.

The minimum number of coupling iterations may be set to a value larger than one (one is the default).

If the data transfers have been under relaxed, you want to ensure a minimum number of coupling iter-

ations is performed so that you iterate out the effect of the under relaxation. Note that the data transfer

convergence criteria would usually make this unnecessary.

The maximum number of coupling iterations should be set to allow complete convergence within each

coupling step. Failure to fully converge within a given coupling step will modify the transient behavior

from that step onward.

Participants

You can connect a participant system's Setup cell to the System Coupling Setup cell in the project

schematic. The system coupling workspace displays a read-only summary of the participant data after

a refresh of the System Coupling Setup cell. The participant summary includes:

System name

The name of the participant as presented in the schematic.

Regions

The collection of regions from and to which data can be transferred. A region is most often a point, line,

surface or volume that is part (or all) of the geometry or topology of a coupling participant. Note, however,

that equations or probe (monitored) values may also be considered as point regions.

Note

System Coupling requires participants to use 3D meshes, with data transfer regions

consisting of element faces from a 3D mesh. System Coupling data transfers cannot exist

in 2D meshes.




Variables

The collection of input and output variables available for data transfer for each region. A variable is a

physical quantity such as force, length, or temperature that can be transferred between regions of par-

ticipant systems. Variables are defined as input or output variables for the specific region.

Note

For structural applications, data transfers are limited to force and displacement; for

thermal heat transfer applications data transfers are limited to temperature, heat flow,

heat transfer coefficient (also known as “convection coefficient”), and near wall temper-

ature (also know as “bulk temperature” or “ambient temperature”).

Data Transfers

A data transfer is defined by one source and one target region, and is able to transfer one variable type

in one direction between two participants.

Each data transfer is defined by a variety of properties such as Source, Target, and Data Transfer

Control. A one-way coupled analysis has data transfer(s) in only one direction between the coupled

participants. In this type of analysis, the source region(s) are defined on only the participant sending

data, and the target regions(s) are defined on only the participant whose solver is receiving the data.

A two-way coupled analysis has data transfers in both directions between the coupled participants. In

this type of analysis, source and target regions are defined on both participants. For example, consider

a coupled two-way fluid-structure interaction analysis where a Fluent system and a Static Structural

system are the two participants. The Fluent system would have a region which is the source region for

the transfer of force, and the target region for the transfer of incremental displacement. The Static

Structural system would have a region that is the source region for the transfer of incremental displace-

ment, and the target region for the transfer of force.

Source/Target

Both Source and Target are each defined by a coupling participant along with a region and a variable

defined within the context of that participant. For a two-way data transfer on one region, you define

two individual data transfers. When you set up your data transfers, a top-down approach should be fol-

lowed when selecting Source and Target. Select in this order:

1. Source Participant

2. Source Region

3. Source Variable

4. Target Participant

5. Target Region

6. Target Variable

Data Transfer Control

Additional properties can be defined to control the way in which the specified data transfers are executed.

For each data transfer you can specify controls that determine:

• When the transfer is to occur.



• The under-relaxation factor applied to the transfer.

• The convergence target.

• If ramping is used when applying data from the source-side to the target-side of the data transfer.

Transfer At

The Transfer At property is used to control when the data transfer is executed by the solver. The

only available option is:

Start of Iteration

Transfer data at the start of every coupling iteration within a coupling step.

Under Relaxation Factor

The factor multiplying the current data transfer values when under-relaxing them against the previous

values. This is overridden with unity in the first coupling iteration of every coupling step only when

the Analysis Type is Transient.

Note

When under-relaxation is used, there is no guarantee that the full value from the

source side of the data transfer is applied to the target by the end of the coupling

step.

RMS Convergence Target

The target value used when evaluating convergence of the data transfer within a coupling iteration.

The default value is 1e-2. The convergence target is RMS-based. For information regarding how this

target is applied, see Evaluating Convergence of Data Transfers (p. 43).

Ramping

The available options for ramping controlled by System Coupling are as follows:

None

The full data transfer value is applied to the target side of the interface for all coupling iterations.

No ramping is the default option.

Linear to Minimum Iterations

Within each coupling step, the ramping factor is used to linearly increase the change in the data

transfer value applied to the target side of the interface. The data transfer value is increased

during each coupling iteration until the specified minimum number of coupling iterations, ��,

is reached. The ramping factor is applied to the change in the data transfer value from the pre-

vious coupling step. If there is no change in this value from the last coupling step, the full data

transfer value is applied to the target side of the interface for all coupling iterations of that

coupling step.

During the ��

coupling iteration (for <� ��), the ramping factor equals � ��. The full

data transfer value is applied for all coupling iterations that are equal to or greater than the

minimum number of coupling iterations. As �� is always reached, the full data transfer

value is always applied by the end of each coupling step. This ramping behavior is demon-

strated in Figure 3: Schematic of the Linear to Minimum Iterations Ramping Concept (p. 16)

for the case where the minimum number of iterations specified is 5.




When ramping using Linear to Minimum Iterations, if the minimum number of iterations is

the same as the maximum number of iterations, then it is unlikely that the data transfer will

converge. It is a best practice for your maximum iterations to be larger than your minimum

iterations.

Figure 3: Schematic of the Linear to Minimum Iterations Ramping Concept

Ramping and under-relaxation are independent operations. Ramping is applied before under-relaxation.

Note

System Coupling’s ramping will interact with ramping behaviors within the participant systems.

To understand the full ramping behavior, verify ramping settings to see if your participant

system is ramping loads received from System Coupling. For ramping behavior in Mechanical,

see System Coupling Related Settings in Mechanical in the ANSYS Mechanical User's Guide.

See Working with Data Transfers (p. 16) for details about how to create, modify data transfers and do

other common operations.

Working with Data Transfers

After you connect a participant system's Setup cell to the System Coupling Setup cell in the project

schematic, the System Coupling workspace displays the regions and variables available to create data

transfers after a Refresh of the Setup cell:

Create Data Transfer

There are different ways to create single and multiple data transfers using the Create Data Transfer

context menu option.

Create uninitialized data transfer

Select the "Data Transfers" tree node in Outline view, then select Create Data Transfer from the

context menu. This creates a new data transfer without any source or target properties defined. You

can later modify the data transfer definition in Properties view.



Create data transfers for two regions from different participants

Select two regions from different participants in the Outline view, then select Create Data Transfer

from the context menu. This creates multiple data transfers that vary based on the following criteria:

• Whether the two regions have the same topology

• Whether the input variable from one region has the same properties (such as the physical type)

as the output variable from the other region

Create data transfers for single region

Select a region from a participant in the Outline view, then select Create Data Transfer from the

context menu. This creates data transfers for each variable associated with the region. If the variable

is an output variable, then the source participant, source region, and source variable are defined for

the new data transfer. If the variable is an input variable, then the target participant, target region,

and target variable are defined for the new data transfer.

Create a data transfer for single variable

Select a region from a participant in Outline view, select a variable in the Properties view, then select

Create Data Transfer from the context menu. This creates a new data transfer. If the selected variable

is an output variable, then the source participant, source region, and source variable are defined for

the new data transfer. If the selected variable is an input variable, then the target participant, target

region, and target variable is defined for the new data transfer.

Modify Data Transfer

Select a data transfer in the Outline view. The Properties view displays all the properties for the data

transfer. You can modify all the properties for the data transfers in the same view.

Rename Data Transfer

Select a data transfer in the Outline view. Double-click to rename the data transfer.

Duplicate Data Transfer

Select one or more data transfers in the Outline view. Right-click and select Duplicate. This operation

creates new data transfers with the same Source, Target, and Data Transfer Control properties. Note that

you can change these properties as needed for these new data transfers.

Suppress Data Transfer

Select one or more data transfers in the Outline view. Right-click and select Suppress to prevent the

data transfer.

Delete Data Transfer

Select one or more data transfers in the Outline view. Right-click and select Delete to remove them.

Note

If the data transfer definition is not valid or the data is invalidated for any reason, the state

of the node will show as a ? and the incorrect properties will need to be changed.




Data Transfer Rules

When you create data transfers in System Coupling, certain rules must be observed in order to correctly

define the analysis.

Note

Participant data transfer regions must consist of triangular or quadrilateral faces. Polyhedral

faces as well as faces with hanging nodes (cut-cells) are not supported in System Coupling.

Currently, the following three types of transfers are supported. Details of these three types of transfers

are given in Table 2: Data Transfers available in System Coupling (p. 18).

• Force transfers

• Motion transfers

• Thermal transfers

Force and motion transfers are typical for fluid-structure interaction problems, where a load to the

structure is transferred from a fluid solver, and the deformations to the fluid are transferred from the

structural solver. There can only be one force transfer and one motion transfer for each data transfer

region.

Thermal transfers can be transferred between ANSYS Fluent and ANSYS Mechanical directly through

System Coupling, or through the coupling of the External Data system. Three thermal transfers are

available, each transferring different thermal variables. The three thermal transfers are described in the

table below.

For one-way thermal transfers, only one of the three options below for thermal transfers can be defined

for a given pair of source and target regions.

For two-way thermal transfers, two data transfers are set up on the same data transfer region. In a two-

way transfer:

• the two variables, heat transfer coefficient and near wall temperature, cannot be transferred on the

same data transfer region as heat flow, and

• a participant’s data transfer region cannot provide and receive the same thermal variable(s); for ex-

ample, Fluent cannot send and receive temperature data on the same data transfer region.

Table 2: Data Transfers available in System Coupling

Data Transfer Dir-

ection

Variable(s) TransferredTransfer Type

Force transfer •• from a fluid solver to

a structural solver

Force (VectorXYZ*)

Motion transfer** •• from a structural

solver to a fluid solv-

er

Incremental displacement (Vec-

torXYZ*)



Data Transfer Dir-

ection

Variable(s) TransferredTransfer Type

1. Temperat-

ure transfer

Thermal

Data

Transfers

• from a structural


er, or

• Temperature (Scalar)

• from a fluid solver to

a structural solver

2. Heat flow

transfer

• from a structural


er, or

• Heat flow (also known as

heat rate) (Scalar)

• from a fluid solver to

a structural solver

3. A pair of

variables***

•• Heat transfer coefficient

(also known as convection

coefficient)** (Scalar)

from a fluid solver to

a structural solver

• Near wall temperature

(also known as bulk tem-

perature, or ambient tem-

perature)** (Scalar)

* Represents the force vector ur� ( �, �, �) and the incremental displacements vector

ur� ( �, �,

�) respectively.

**In a general coupled analysis, when the solver receiving the motion (such as Fluent) solves before or

simultaneously to the solver sending the motion (such as Mechanical), then the incremental displacement

transferred during the first coupling iteration of each coupling step is identically zero. This behavior

can be changed by using GeneralAnalysis_IncrDisp_InitIterationValue_Zero in the

Expert Settings (p. 24).

***You must correctly define both variables in the data transfer in order for this thermal transfer to be

valid.

Note

For a given target region, there can only be one source region. However, a given source region

can send data to multiple target regions. In other words, 1-to-M data transfers are supported,

where M is an integer and is greater than or equal to 1. Note that M-to-1 data transfers are

not supported.

Execution Control

Execution Control has the following capabilities:

Co-Simulation Participant Sequencing

Debug Output Control

Intermediate Restart Data Output




Co-Simulation Participant Sequencing

The System Coupling system offers comprehensive control over the sequencing of co-simulation parti-

cipants, and specifically over the data transfers that are required to obtain a solution. This is controlled

through the settings in the Co-Sim Sequence. The participants are sequenced by assigning a sequence

value, which is an integer value between 1 and the number of participants in the analysis, to each

participant. Each participant executes its solutions (that is, all required data transfers, followed by ob-

taining the equation solution) in the order of its sequence value, where the participants with the lower

sequence values execute first. The coupled analysis will use sequential solutions or simultaneous solutions,

depending on the assigned sequence values. This is described in more detail below.

Note

To improve solution stability, sequential solutions are used by default. Note as well that,

to facilitate synchronization of interface geometry, participants that consume geomet-

rical or mesh deformations (for example, the Fluids solver in a Fluid Structure Interaction

analysis) are automatically assigned larger sequence values by default.

Additional information can also be found in "Best Practice Guidelines for Using System Coupling" (p. 73).

Sequential Solutions

A sequential solution is done when all co-simulation participants are assigned different solution sequence

values. In particular, participants perform their solutions (that is, all required data transfers, followed by

obtaining the equation solution) in the order of the sequence values specified in the user interface.

Sequential solutions are optimal for analyses that involve strong physical couplings, because the most

recent information from one participant is always used by subsequent participants. This typically

translates into requiring the fewest coupling iteration per coupling step to reach a converged solution.

However, it may not yield the shortest (wall-clock) solution time if the participants are run on different

CPUs.

Simultaneous Solutions

A simultaneous solution is done when one or more co-simulation participants are assigned identical

solution sequence values. In particular, when the same sequence value is applied to multiple participants,

then all those participants perform their respective data transfers, after which those same participants

perform their equation solutions simultaneously.

Simultaneous solutions are optimal for analyses that involve weak physical couplings because the most

recent information from one co-simulation participant is not required by other simultaneously executed

participants in order to reach a converged solution. Additionally, the overall (wall-clock) solution time

may be reduced if the simultaneously executed participants are run on different CPUs. However, if used

with co-simulation participants that exhibit strong physical couplings, simultaneous solutions may ad-

versely affect the rate of convergence, and possibly lead to divergence.

Debug Output Control

The Debug Output entity under Execution Control in the outline model controls the level of debug

information written in the System Coupling Log (*.scl ) file during the execution of the solution. The

basic level of detail included is controlled using one of the following levels:

• None



• Level 1

• Level 2

• Level 3

• Level 4

• All Levels

By default, the value set for the Global Level is applied to all stages of solution execution listed below.

To use a different value for one or more of the specific stages of solution execution, change the value

from Use Global Level to the desired output level.

Note that stages of solution execution that are associated with Data Transfers are grouped together,

and have their own default Data Transfers Level value. To use a different value for one or more of

these stages of solution execution, change the value from Use Data Transfers Level to the desired

output level.

The following properties control the debug level for different sections of the log:

Startup

Controls the level of output from the start of the coupling service until creation of the "Summary of SC

Setup" banner in the SCL file.

Participant Connection

Controls the level of output from the end of the setup validation until the Initial Synchronization syn-

chronization point (that is, between the Setup Validation and System Coupling Summary banners).

Analysis Initialization

Controls the level of output from the end of the setup validation until the Analysis Initialization syn-

chronization point (that is, between the System Coupling Summary and Solution banners).

Solution Initialization

Controls the level of output during the setup of coupling steps and coupling iterations. This output does

not include information related to the data transfers.

Data Transfers

Specifies the debug output generated for data transfers. Note that header information for mapping is

generated whenever the mesh coordinate or mesh topology output is requested. Similarly, header in-

formation for the data transfers is generated whenever the transfer data output is requested.

Data Transfers Level

Provides the default level for the different debug output controls in the Data Transfers group. If

the debug level of any property in the Data Transfers group is set to Default, then the debug level

of that entry is governed by the level set here. If the Data Transfers Level itself is set to Use Global

Level, then it derives its value from the default level defined for all debug output controls.

Source Mesh Coordinates

Controls the level of output for mesh coordinates of the source region in all data transfers.

Source Mesh Topology

Controls the level of output for mesh topology (elements and nodes) of the source region in all data

transfers.




Source Data

Controls the level of output for the source data in all data transfers.

Target Mesh Coordinates

Controls the level of output for mesh coordinates of the source region in all data transfers.

Target Mesh Topology

Controls the level of output for mesh topology (elements and nodes) of the source region in all data

transfers.

Target Data

Controls the level of output for the target data in all data transfers.

Convergence Checks

Controls the level of output from the Check Convergence synchronization point until the next synchron-

ization point, which may be either Shutdown or Solution.

Shutdown

Controls the level of output after the Shutdown synchronization point.

For information about synchronization points, see Process Synchronization and Analysis Evolution (p. 41).

Note

The debug level for all the properties, except Default, can be set at any level. For the Default

property, the available levels are from None to All Levels. Increasing levels always generate

more detailed output. Note, as well, that the output level settings for each of the mesh co-

ordinates, topology, and transfer data, control the number of lines of output generated.

Specifically, 10L lines of data will be written for an output level setting of L (for example, 100

lines will be written for an output level of 2, or Level 2).

Intermediate Restart Data Output

The Intermediate Restart Data Output entity under Execution Control in the outline model allows

the selection of time points at which restart data should be generated during the execution of the

solution. Depending on the participant, the restart data may or may not be the same as the results

data. Writing of results data for post-processing should be set from within the participant setup cell.

Important

During execution of the coupled analysis, co-simulation participants will automatically be

requested to generate intermediate restart data at the same frequency as the System

Coupling service. Note that this feature only affects the frequency at which data is generated;

the content of data is determined by the participant. To see if this feature is supported, see

Supported System Couplings (p. 3).

Choose one of the following options to control when restart data is produced.

None

No intermediate restart output files are generated using this option. This option is enabled by default.



All steps

Restart output files are generated at the end of each coupling step.

At Step Interval

Restart output files are generated at the end of the coupling steps corresponding to the interval specified

in the Step Interval box below.

Note

If you specify a Step Interval that is above or below the allowed limit, an error is dis-

played; change the Step Interval as required.

Validation and State of the System Coupling Setup Cell

Validation of the Setup cell depends upon the validation of the individual nodes in the Tree View (for

example, Analysis Settings and Data Transfer). If any of these nodes is invalid, it would be marked

by a ? (Attention Required) in front of the Setup cell. Details regarding why validation failed are

presented when the mouse pointer is hovered over the ? symbol.

System Coupling Setup Cell Context Menus

The System Coupling Setup cell has several context menus:

• Start/Stop highlighting linked nodes: From the Setup cell, this option controls whether cells that are

related to the selected cell are highlighted in the Outline view.

• Create Data Transfer: From Data Transfers you can create one or more data transfers using this context

menu. See Working with Data Transfers (p. 16) for details.

• Auto Show/Hide

• Toolbar Option

• Rename: From Data Transfers you can rename the selected data transfers using this context menu. See

Working with Data Transfers (p. 16) for details.

• Duplicate: From Data Transfers you can duplicate the selected data transfers using this context menu.

See Working with Data Transfers (p. 16) for details.

• Display Validation Failure: Select this to display error messages when System Coupling setup settings

are found to be incorrect due to validation problems.

• Add Property: From Execution Control>Expert Settings, you can add specific expert settings. See Expert

Settings (p. 24) for details about these settings.

• Remove Property: From Execution Control>Expert Settings, you can remove specific expert settings.

See Expert Settings (p. 24) for details about these settings.

• Read restart points: From Properties of Analysis Settings>Initialization Controls>Coupling Initializa-

tion, you can use this command to populate the list of restart points. This command is useful for abnormal

situations such as a workbench crash. In such situations, the restart point list may be empty even though

the intermediate restart files exist on your disk. Read restart points is used to repopulate your list of restart

points, so that you can restart from a previously saved restart point.




See Understanding Cell States in the Workbench User’s Guide for detailed information on typical cell

states.

Expert Settings

This subsection is used to specify the expert settings that are available. Expert settings provide you

with additional advanced controls for many of the settings available in the Outline and Properties

views under the Setup branch.

• General Expert Settings

– DumpInterfaceMeshes (string)

The only valid value for this setting is CFDPost . When this expert setting is used, files named

<Name of Data Transfer>source.csv or <Name of Data Transfer>target.csvare generated during the mapping process. These files report values of 0 and 1 for unmapped and

mapped nodes, respectively. These files are appropriate for import into CFD-Post as user defined

surfaces for the visualization of mapping data.

– MeshSyncOption (integer)

Value is 0, 1, 2, or 3 (default: 0). This setting is only relevant for coupled analyses with a participant

that consumes geometric data (for example, the Fluids solver in a Fluid Structure Interaction ana-

lysis, which receives displacement data). This setting can be used when the solution of the participant

consuming geometrical data is either sequenced identically as, or sequenced before, the solution

of the participant that provides the geometric data. Available options are:

→0 (default): If the maximum number of coupling iterations per coupling step is 1, then the solution

sequence is changed so that the participant that consumes geometrical data is solved last. If the

maximum number of coupling iterations per coupling step is greater than 1, then one additional

coupling iteration is performed at the end of the coupling step and only the participant that

consumes geometrical data is re-solved.

→1: Regardless of the maximum number of coupling iterations per coupling step, the solution

sequence is changed so that within each coupling iteration, the participant that consumes geo-

metrical data is solved last.

→2: Regardless of the maximum number of coupling iterations per coupling step, one additional

coupling iteration is performed at the end of the coupling step and only the participant that

consumes geometrical data is re-solved.

→3: No setup modifications are applied, and the solution proceeds with the specified participant

sequencing.

– GeneralAnalysis_IncrDisp_InitIterationValue_Zero (integer)

Value is 0 or 1 (default: 1). This setting is only relevant in a general coupled analysis, when displace-

ment is transferred, and when the solver receiving the displacement (such as Fluent) solves before

or simultaneously to the solver sending the displacement data (such as Mechanical).

→1: During the first coupling iteration of each coupling step the displacement transferred to the target

is 0 [m] (irrespective of the value provided by the source). This override of the transfer value is to

avoid possible double displacement, which could create folding of the mesh.



→0: The value for displacement provided by the source is transferred with no interference by this expert

setting (this value transferred may be modified by other settings such as ramping).

• Participant Variable Initial Value Settings

The following expert settings are useful for overriding the default initial values of variables of a given

type for all participants. These initial values are currently used in the ramping as well as the under-

relaxation of data transfers. Note that for the ramping algorithm, the reference target-side value for

displacement is always 0.0 [m]. The expert settings below will have no effect on the value used in

this case.

– Participant_Variable_InitValue_IncrDisp_X (real)

Participant_Variable_InitValue_IncrDisp_Y (real)

Participant_Variable_InitValue_IncrDisp_Z (real)

Replace initial value for Cartesian components of all variables of type "Incremental Displacement"

for all coupling participants. Default is 0.0 [m].

– Participant_Variable_InitValue_Force_X (real)

Participant_Variable_InitValue_Force_Y (real)

Participant_Variable_InitValue_Force_Z (real)

Replace initial value for Cartesian components of all variables of type "Force" for all coupling parti-

cipants. Default is 0.0 [N].

– Participant_Variable_InitValue_Temperature (real)

Replace initial value for all variables of type "Temperature" for all coupling participants (variables

include temperature and near wall temperature). Default is 295.15 [K].

– Participant_Variable_InitValue_HeatRate (real)

Replace initial value for all variables of type "Heat Rate" for all coupling participants. Default is 0.0

[W].

– Participant_Variable_InitValue_HeatTransferCoef (real)

Replace initial value for all variables of type "Heat Transfer Coefficient" for all coupling participants.

Default is 0.0 [W m^-2 K^-1].

• Data Transfer Control Settings

The following expert settings are useful for controlling the behavior of data transfers.

– DataTransfer_ScaleFactor_Force (double)

Scale, by the factor specified, source values for all data transfers of Force variables. Default value

is 1.0.

– DataTransfer_ScaleFactor_HeatRate (double)




Scale, by the factor specified, source values for all data transfers of Heat Rate variables. Default

value is 1.0.

– DataTransfer_ScaleFactor_HeatTransferCoef (double)

Scale, by the factor specified, source values for all data transfers of Heat Transfer Coefficient variables.

Default value is 1.0.

– DataTransfer_ScaleFactor_IncrDisp (double)

Scale, by the factor specified, source values for all data transfers of Incremental Displacement

variables. Default value is 1.0.

– DataTransfer_ScaleFactor_Temperature (double)

Scale, by the factor specified, source values for all data transfers of Temperature variables. Default

value is 1.0.

• SC Log Output Control Settings

The following expert settings are useful for controlling the output of various supplemental diagnostics

to the SC log file:

– DTDiagShowRMSChange (string)

Activates reporting of RMS change in data transfers if set to true. Default is ‘False’.

When RMS change is the type of data checked against the convergence target (this is the default),

this expert setting does nothing.

– DTDiagShowMaxChange (string)

Activates reporting of Max change in data transfers if set to true. Default is ‘False’.

If Max change is the type of data checked against the convergence target, this expert setting does

nothing. Note that the type of data checked (RMS change or Max change) can only be changed

through the System Coupling Input File.

– DTDiagShowMinValue (string)

Activates reporting of minimum nodal value in data transfers if set to true. Default is ‘False’.

– DTDiagShowMaxValue (string)

Activates reporting of maximum nodal value in data transfers if set to true. Default is ‘False’.

– DTDiagShowAvgValue (string)

Activates reporting of average nodal value in data transfers if set to true. Default is ‘False’.

– DTDiagShowSum (string)

Activates reporting of sum of nodal values in data transfers if set to true. Default is ‘False’.

– DTDiagShowAll (string)



Activates reporting of all diagnostics of nodal values in data transfers if set to true. Default is ‘False’.

• Expert Settings Related to Mapping

The coupling service uses a Profile Preserving mapping (ProfMap) for non-conservative quantities (for

example, displacement) data transfers, and a Conservative mapping (ConsMap) for conservative

quantities (for example, forces).

– ProfMapBucketScale (integer)

Value (ranging from 0 to 100, default: 50) that represents the number of discrete search ‘buckets’,

as a percentage of the number of nodes, to use during mapping. The objective is to generate

‘buckets’ that will contain roughly equal numbers of nodes. This setting will affect the speed of

the mapping, but it should not affect the outcome.

– ProfMapBucketTol (double)

Value (ranging from 0 to 1, default: 1e-4) that is used to create a bounding region around each

target node. The bounding region is used to increase the number of buckets that will be included

in the Bucket Surface Algorithm's search, which in some cases will improve the number of mapped

nodes.

– ProfMapEdgeTol (double)

Value (ranging from 0 to 1, default: 0.05 in natural coordinate space) that specifies the tolerance

within which a target node may be found in a source element. See the discussion on Bucket Sur-

face (p. 48) mapping algorithm in the section Mapping Algorithms (p. 46) for more information

regarding this tolerance setting.

– ProfMapTolOption (integer)

Value is either 0 or 1 (default: 0), where 0 indicates that the specified tolerance is relative to the

maximum Cartesian extent of the region being mapped, and 1 indicates that the specified tolerance

is absolute (using the same units as the mesh coordinates).

– ProfMapTol (double)

Value (ranging from 0 to 1, default: 1e-6) that specifies the tolerance for the 'gap' distance between

a target node and the source element that it is mapped to.

– ProfMapEnforceTol (integer)

Value is either 0 or 1 (default: 0), where 0 indicates that the distance between a target node and

the source element that it is mapped to (also known as the ‘gap’ distance) is not checked against

the tolerance specified with the expert setting ProfMapTol . Target nodes with final ‘gap’ distances

larger than the specified tolerance will be reported as mapped in the SCL file. These nodes are

mapped to the source nodes like all of the other mapped nodes and given a value accordingly.

A setting of 1 (which means on) indicates that such a check is performed. Target nodes with final

‘gap’ distances larger than the specified tolerance will be reported as unmapped in the SCL file.

These nodes are mapped to the source nodes like all of the other mapped nodes and given a value

accordingly.

– ConsMapPixelRes (integer)




Value, (ranging from 10 to 256, default: 100), that indicates the number of pixels to use when

forming the surfaces of intersection for each pair of source and target mesh element faces on the

interface. Larger values are needed if interface mesh lines are very nearly coincident. Any value

entered that is less than 10 or greater than 256 will be reset to 100 automatically.

– ConsMapTol (double)

Value, (ranging from 0.1 and 1, default: 0.1), that specifies the tolerance, in the element-face-normal

direction, to use when determining whether the source and target meshes map to one another.

This tolerance is normalized by the local element size. Any value entered that is less than 0.1 or

greater than 1 will be reset to 0.1 automatically.


This section describes:

• All the settings that appear in the Outline and Properties views under the “Solution” branch.

• Context menus (that is, the menus that appear with a right-click) for the Solution cell.


Solution Information

Chart Monitors

Validation and State of the System Coupling Solution Cell

System Coupling Solution Cell Context Menus

Solution Information

Solution information is automatically generated for output of the system coupling service and the

coupling participants. Figure 4: An Example of the Solution Information Branch (p. 29) displays an example

of the “Solution Information” branch from the Outline view. Select an entry from the listed solution

information sources to display its output in the Solution Information view.

Note

The default behavior of the Solution Information view is to always show the latest inform-

ation in the log file. Each time new information is added, the file will automatically scroll to

the end. However, if you move the vertical scroll bar away from the bottom, the view will

not scroll to the end when new information is added until you move the scroll bar back to

the end.

There are also some keyboard short-cuts that are available when operating in this view:

• Page Up scrolls up one page.

• Page Down scrolls down one page.

• Ctrl+Home jumps to the top of the log.

• Ctrl+End jumps to the bottom of the log.



Figure 4: An Example of the Solution Information Branch

For additional details about the solution information displayed for the coupling service, see System

Coupling Service Log File (scLog.scl_, scLog_##.scl ) (p. 57). For additional details about

solution information displayed for coupling participants, see Supported System Couplings (p. 3).

Chart Monitors

Convergence data is available for plotting once the solution is running or has been completed. The

data is available for plotting against different levels (X axis data). The higher (coarser) levels at which

the data is present are referred to as parent levels, where as the lower (finer) levels at which the data

is present are referred to as child levels. Any data present in a child level are also available at the parent

level for plotting. For example: In the graphic that follows, the flow chart shows different variables and

levels for a sample run. "Coupling Step" is the parent level for "Coupling Iteration", whereas "Solver 1

Step", "Solver 1 Iteration", "Solver 2 Step", and "Solver 2 Iteration" are child levels of "Coupling Iteration".

There are two variables, "Variable 1" and "Variable 2", present. "Variable 1" is present at "Solver 1 Iteration"

and hence is available for plotting at "Solver 1 Iteration" or any of its parents, that is, "Solver 1 Step",

"Coupling Iteration" or "Coupling Step". Similarly, "Variable 2" is available for plotting at "Solver 2 Itera-

tion", "Solver 2 Step", "Coupling Iteration", and "Coupling Step".

Chart Properties

Axis X Property:

• Quantity: The level at which the X data for the variables is plotted. This can be any level at which the

data is available. For example: For a variable "Data Transfer:Change:RMS", the available levels can be

"Coupling Step" and "Coupling Iteration". The X axis level can be defined by selecting an option in

the drop-down options list in the Properties view of a chart.

Axis Y Property:

• Title: The title of the axis




Properties Supported for Both Axes:

• Scale: The scale of the axis. Scale can be defined as Linear, Common Log (Log base 10) or Natural

Log.

• Automatic Range: The property to define whether or not automatic scaling should be applied to the

axis, or whether the RangeMin and RangeMax should be used.

• Range Minimum: The minimum range of the values in this axis.

• Range Maximum: The maximum range of the values in this axis.

Chart Variable

A variable that is plotted in the convergence chart. These variables are organized according to coupling

participants and include:

• measures of convergence obtained from co-simulation participants (for example, solver residuals)

• the change (RMS or maximum) in data transfer values

• diagnostic values (for example, minimum, maximum, average, and sum) taken from the nodal data asso-

ciated with data transfers

Chart Variable Properties

Refinement Level

The data plotted at the level defined by the X axis can be further refined to any of the child levels of

the X axis. For example: For X axis level defined at the "Coupling Step", the X data values for a variable

can be refined to the "Coupling Iteration" level. In this case the intermediate values available at "Coupling

Iteration" level between consecutive "Coupling Steps" are distributed equally between the coupling

steps; that is, if "Coupling Step" 2 has three "Coupling Iterations", then the data points are plotted at

1.33, 1.66, and 2. The refinement level can be defined by selecting an option in the drop down options

list in the Properties view of a chart.

Style

• Color: The line color of the chart variable in a plot

• Line Width: The width of the line drawn for this chart variable in pixels

• Symbol Size: The size of a symbol in pixels when a symbol is drawn for this variable

Working with Convergence Charts

The following context menu options are available:

Create Convergence Chart

You can create convergence charts by using the Create Convergence Chart context menu option. Right-

click the "Chart Monitors" tree node in the Outline view, then select Create Convergence Chart from

the context menu. This creates a new convergence chart without any variables defined. The default X

axis level is "Coupling Iteration".



Add Variable

Once the solution is running or completed, variables to be plotted can be added to a convergence chart.

Select a convergence chart in the Outline view, and then select Add Variable from the context menu.

Chartable data of interest are subsequently selected and added to the chart via the context menus

presented. The default refinement level for the added variable is set to the X axis level. If the data for

the new variable is not available at the level defined by the X axis, the X axis level and the refinement

level for the new variable are set to "Coupling Iteration".

Remove Variable

A variable included in the chart can be removed using the Remove Variable context menu option. This

removes the selected variable from the chart.

Delete Variable

A variable included in the chart can be removed using the Delete context menu option.

Delete Convergence Chart

A convergence chart can be deleted using the Delete context menu option.

Editing Chart and Chart Variable Properties

Chart and Chart Variable properties are displayed and can be edited in Properties view based on selection

in Outline view.

Note

When the solution is started, a default chart is added if one is not already present. The default

variables added correspond to the RMS Change in data on the target side of all data transfers.

For example if "Data Transfer" and "Data Transfer 2" are defined with target participants

equal to "Transient Structural" and "Fluid Flow", respectively, then the chart variables "Tran-

sient Structural: Data Transfer: Change: RMS" and "Fluid Flow: Data Transfer 2: Change: RMS"

are added to the default chart. If you add/delete variables to the default chart, then new

variables are not added by default on consecutive runs.

Using the Scene Chart Monitor View

Chart Zoom, Pan, and Fit

You can manipulate the display of a chart using the zoom, pan, and fit features.

• Zoom by using the mouse wheel or Shift+middle mouse button

• Box zoom by using the right mouse button

• Pan by using Ctrl+middle mouse button

• Fit by using the F key.

Saving a Chart

You can save the chart that you are viewing as a graphic. To do so, right-click the background of the

chart and select Save Image As. In the dialog box that appears, you will see a small image of the chart,

and can select the Size (resolution) that will be used when saving the chart. Click the button and

navigate to the folder where you want to save the file. Enter a file name. You can select either .png or

.bmp as the graphic file type. Click Save to select that file path as your save location. Click OK to save

the file to the location that you selected, with the resolution that you have selected.




Validation and State of the System Coupling Solution Cell

The state of the Solution cell is coupled to the states of the Solution cells for all co-simulation participants.

In particular, all coupled Solution cells will have the same state, which will reflect the least complete

state of all coupled cells.

System Coupling Solution Cell Context Menus

The System Coupling Solution cell has several context menus:

• Create Convergence Chart: From Chart Monitors you can create a convergence plot or chart monitor

using this context menu.

• Update, Refresh, Clear Generated Data, Reset: From the Solution cell, you can Update, Refresh, Clear

Generated Data, or Reset the Solution using the context menu. These commands are the same as those

available on the Solution cell for the corresponding System Coupling system on the Project Schematic

page.

• Add/Remove Variable: From Chart you can add or remove variables from the selected chart using the

context menu. For details, see Working with Convergence Charts (p. 30).

• Display Validation Failure: Select this to display error messages when System Coupling solution items

(for example, chart monitors) are found to be incorrect due to validation problems.

Note

If a coupled analysis is interrupted before reaching the specified coupling duration, then the

Solution cells will remain in an ‘Update Required’ state once execution stops. This reflects

the need to (re)update in order to complete the analysis, as specified during the setup.

However, downstream Results cells may be refreshed and/or updated to review the results

generated up to the point at which the analysis was interrupted.

See Understanding Cell States in the Workbench User’s Guide for detailed information on typical cell

states.



Workflows for System Coupling

This chapter describes general issues common to working with System Coupling systems.

Executing System Couplings Using the Command Line

Restarting a System Coupling Analysis

Stopping the Coupled Analysis Run

Executing System Couplings Using the Command Line

You can set up system coupling simulations by using the command line, rather than by using the

Workbench user interface.

To perform a system coupling simulation from the command line, you need to ensure paths to all required

scripts and executables are added to the PATH environment variable so that these applications can be

launched from command line.

Tip

Search your installation to help resolve any missing dynamic libraries.

To run an analysis from the command line, execute the steps below. If you would like an example of

this process, the tutorial Oscillating Plate with Two-Way Fluid-Structure Interaction provides detailed

steps on how to use the Command Line in the section Executing the Coupled Analysis from the Command

Line.

1. Generate the System Coupling Input file and place this file in the desired working directory for the

Coupling Service. To do this, enter (double click) the System Coupling Setup cell in the Workbench

schematic, and select the Export SCI File option from the File menu. Note that this option is only

available when the state of the Setup cell is up-to-date.

2. Generate all input files required for the co-simulation participants (that is, input files required for the

solvers involved in the coupling) and place these files in the respective desired working directories.

3. The command to start the Coupling Service differs between Linux and Windows:

• Linux:

.workbench -cmd ansys.services.systemcoupling.exe -inputFile oscillating_plate.sci

where .workbench is a script located in /ansys_inc/v150/aisol on Linux.

The typical location of the executable on Linux 64-bit Workbench installations is:

/ansys_inc/v150/aisol/CommonFiles/linx64

• Windows:

ansys.services.systemcoupling.exe -inputFile oscillating_plate.sci



The typical location of the executable on Windows 64- and 32-bit Workbench installations are,

respectively:

C:~\ANSYS Inc\v150\aisol\bin\winx64C:~\ANSYS Inc\v150\aisol\bin\intel

These commands launch the Coupling Service and create a System Coupling Server file (scServ-er.scs ) in the working directory. As described in System Coupling Server File (scServ-er.scs ) (p. 56), this file contains information needed to start each of the co-simulation participants,

specifically port and host information for the coupling service and identifiers for the participants.

Additional information needed to run from the command line is accessible below for each of the

co-simulation participants that support system couplings.

For more information about command line execution and options for supported co-simulation parti-

cipants, see Supported System Couplings (p. 3). Co-simulation participants will tend to use a common

set of system coupling related command line options (such as -schost , -scport , and -scname ).

You are strongly encouraged, however, to develop some expertise in running each of the participants

without system couplings before attempting to execute coupled analyses from the command line.

Additional system coupling command line information can also be found in the following section:

System Coupling Command Line Options

System Coupling Command Line Options

The following command-line options are available in the command line:

-debugLevel [ 0 | 1 | 2 | 3 | 4 | 5 ]Generates debug output to the System Coupling Log (.scl) file. The level of debug output increases with

each level, with the default (0) providing no debug output and level 5 providing the most complete

debug output.

-extractInputFile input_file_nameExtracts the content of an identified System Coupling Input (scInput.sci ) file that is contained in

the specified System Coupling Results (scResults_##_######.scr ) file (via -resultFile ). Valid

names are the ones returned by the -listInputFiles command line option.

-helpDisplays the option summary.

-inputFile path_to_sci_fileInputs to the coupled analysis are extracted from the specified System Coupling Input file, where

path_to_sci_file is the location of the input file.

-listInputFilesLists all of the input files stored in the specified System Coupling Results file (via -resultFile ). Output

is written to the System Coupling Log file for the run.

-logFile path_to_scl_fileGenerates the System Coupling Log file with a specific name in a specific directory, where

path_to_scl_file is the location of the generated log file. The default log file name is scLog.scland will be generated in the same directory from which the coupling services executable is run.



-resultFile path_to_scr_fileContinue the analysis from the specified System Coupling Results file, where path_to_scr_file is

the location of the results file. Note that if the -inputFile option is also used, then inputs to the

coupled analysis are extracted from that file.

For more information about command line execution and options for supported co-simulation parti-

cipants, see Supported System Couplings (p. 3).


The sections below walks you through the steps needed to restart a coupled analysis using System

Coupling, but you will also need restart information specific to the participants connected to your System

Coupling system. See Supported System Couplings for a list of supported systems and references to

their corresponding documentation regarding restarts.

Restarting a coupled analysis is further described in the following sections:

Generating Restart Files

Executing the Restart Run

Recovering from a Workbench Crash

Note

• The System Coupling Results file generated by the coupling service contains all the information

and data that are required to restart the coupling service only. Information and data that are

required to restart the coupling participants, as well as the act of restarting those participants,

are managed by the participants themselves.

• The convergence history for a restarted run is generally not identical to that observed in a

continuous run. There are two factors contributing to changes in convergence: interfaces are

re-mapped upon restart, thereby changing the interpolation weights; and restart- and continu-

ous-run convergence histories are not always identical (for example, the HHT transient discret-

ization used by ANSYS Mechanical will not yield identical convergence histories while the

Newmark discretization will).

• Changes in convergence history across restarts will yield changes in solution values if solutions

are not fully converged within coupling steps.

Generating Restart Files

Restarts of a system coupling analysis requires corresponding restart points to exist in the coupling

service and in each of the solvers participating in the analysis.

During a coupled analysis, restart points that contain information for restarts need to be created by all

of the systems involved in your coupled analysis. System Coupling’s restart file is the System Coupling

Results (scr) file. Creation of restart points is controlled in System Coupling to ensure participant solvers

are writing data at synchronized coupling steps.

To generate restart files for a coupled analysis, follow the steps below:

1. Before starting the analysis’ initial run, ensure that all coupling participants are set up to save (or retain)

the corresponding restart points during the run. For information on how to do this, see Supported




System Couplings for a list of supported systems and references to their corresponding documentation

regarding restarts.

2. Set up the System Coupling system to control the creation of restart points at certain intervals during

the coupled analysis run.

a. From the Project Schematic, double-click System Coupling's Setup cell to open the System Coupling

tab.

b. In System Coupling's Outline view on the left, select System Coupling > Setup > Execution

Control > Intermediate Restart Data Output.

c. In the Properties view, under Output Frequency, select the appropriate setting. See Intermediate

Restart Data Output for more information.

Executing the Restart Run

Once the coupled analysis run is finished or interrupted, or if the solution fails, you can restart this run

from any of the saved restart points. You need to select the same restart point in all coupling participants,

as well as in the System Coupling system.

To execute the restart run:

1. Specify a restart point in each participant connected to System Coupling. Make sure that these restart

points correspond to the restart point you will choose in System Coupling.

For information on how to do this for participant systems in your coupled analysis, see Supported

System Couplings for a list of supported systems and references to their corresponding restart

documentation.

2. If setup changes in the participant systems are needed before restarting, make these required changes.



documentation.

3. In some cases, setup changes are desired or are required to avoid failure of the coupled analysis. To

make these changes:

a. Double-click the System Coupling Setup cell or Solution cell to open the System Coupling tab.

b. Modify the required settings in System Coupling. Setup changes commonly include changes to a

combination of the following:

• Coupling analysis type

• Coupling initialization and duration settings

• Coupling step size

• Minimum and maximum number of coupling iterations per coupling step

• Data transfer convergence targets and under-relaxation factors



If running your analysis from the command line, note that each of the –inputFile and –res-ultFile command line options are required for this type of restart. If no modifications were

made, only the –resultFile command line option is required for the restart.

4. Select the restart point for the System Coupling system. To do this:

a. If the System Coupling tab is not already open, double-click the System Coupling Setup cell or

Solution cell to open the System Coupling tab.

b. In the System Coupling tab, select Analysis Settings, then in Properties of Analysis Settings >

Coupling Initialization, pick a restart point that corresponds to the restart point you selected in

the participant systems.

5. Start your restart run. To do this, in the System Coupling tab, right-click Solution and select Update.

Your restarted coupled analysis will now begin to solve.

Recovering from a Workbench Crash

Workbench or one of the components may crash such that restart files are available but they are not

recognized or populated in the Workbench project. If this is the case, you will be able to recover your

project and restart your analysis using the steps below.

The usual project directory (ProjectName_files ) contains the latest System Coupling results and

restart points (these solvers use the live project instead of running in a temporary directory).

Note that the .backup directory contains the original version of any files which have been modified

since the last save. These files are useful to recover the last saved state, but they are not useful for re-

starting your analysis.

To recover the project to be able to restart from a restart point:

1. Launch Workbench and open the project. Since the project was not closed down cleanly, a lock file will

exist. Select Unlock in the dialog box that appears.

2. The next dialog box that appears asks if you want to recover the last saved state before opening. Select

No here despite the warnings.

Your Project Schematic now shows a state as if the solution had not started, but examination of

the project files shows that backup files are available. Your Workbench project will not know about

these files.

3. Populate the restart data from the participant systems connected to System Coupling. Make sure that

these restart points correspond to the restart point chosen in System Coupling.



documentation.

4. Recover the System Coupling restart points:

a. On the Project Schematic, right-click System Coupling's Setup cell, and select Update.

b. Double-click the System Coupling Setup cell to open the System Coupling tab.




c. Select Analysis Settings, then in Properties of Analysis Settings, right-click Coupling Initialization

and select Read Restart Points.

The restart points will now be available in System Coupling as usual.

d. In Properties of Analysis Settings > Coupling Initialization, pick a restart point that corresponds

to the restart point you selected in the participant systems.

5. You can now start your restart run. To do this, in the System Coupling tab, right-click Solution and select

Update. Your restarted coupled analysis will now begin to solve.


During the analysis run, you may wish to interrupt or abort the analysis before it is completed. The in-

terrupted analysis can be thought of as a clean stop, where the run continues until the current coupling

step is finished, and the restart data are generated. Such a run can be restarted later from end of the

coupling step in which it was stopped, as described in Restarting a System Coupling Analysis (p. 35).

The aborted analysis, on the other hand, terminates the run immediately. This run cannot be restarted

from the coupling step in which it was stopped.

The workflow for stopping the coupled analysis run in Workbench is as follows:

1. Start the analysis by selecting Update from the context menu of the Solution cell of the System Coupling

component.

2. In the Progress view of Workbench, click the Stop button .

3. A popup window, shown in Figure 5: Interrupt Prompt from Workbench (p. 38), will appear asking how

the run should be stopped.

Figure 5: Interrupt Prompt from Workbench

You can choose from the following options:

• Select Interrupt to perform a clean shutdown. The analysis will stop once the current coupling

step is completed.

• Select Abort to stop the analysis run immediately. All available generated data will be discarded.

• Select Cancel to continue with the current run.

4. See Restarting a System Coupling Analysis (p. 35) for information on how to restart the coupled analysis

run.



If you are running your analysis from the command line, to stop a run an scStop.stop file must be

created in the working directory for the System Coupling service. See System Coupling Service Shutdown

File (scStop.stop ) (p. 56) for more information.




Understanding the System Coupling Service

This chapter provides information about the System Coupling Service used in the execution of coupled

analyses. The two main roles of the coupling service are: coupling management, and the mapping of

data transfers. This chapter also describes the various files used by and generated by the coupling service.

Coupling Management

Data Transfers

Files Used by the Coupling Service

Files Generated by Coupling Service

Understanding the System Coupling Input File

Understanding the System Coupling Log File

Coupling Management

The primary role of the System Coupling Service is to manage the coupled analysis. There are three

aspects to this:

• Inter-Process Communication

• Process Synchronization and Analysis Evolution

• Convergence Management

For more information, see the following sections.

Inter-Process Communication

Process Synchronization and Analysis Evolution

Convergence Management

Evaluating Convergence of Data Transfers

Inter-Process Communication

The coupling service and participants, which are often highly optimized physics solvers, are executed

as independent computational processes, and this introduces the need for Inter-Process Communication

(IPC). This communication is realized using a proprietary, light-weight, TCP/IP based client-server infra-

structure that does not interact with other communication mechanisms like the Message Passing Interface

(MPI).

All high level communication needed for process synchronization, brokering data transfers and managing

convergence between the coupling service and participants are defined in terms of Application Pro-

gramming Interfaces (APIs) that use the low level IPC infrastructure.

Process Synchronization and Analysis Evolution

The coupling service and participants advance synchronously through a coupled analysis. High-level

synchronization is managed with the use of synchronization points, and low-level synchronization,

between synchronization points, is managed using a token-based protocol.



The five primary synchronization points used to manage advancement through the coupled analysis

are shown in Figure 6: Execution Sequence Diagram for the Coupling Service and Co-Simulation Parti-

cipants (p. 42). This figure also features notes regarding the processing that occurs between these

points, as well as the coupling step and iteration loop structure. Each of these synchronization points,

shown in dark gray, represents a gateway beyond which a given process may not advance until all

other processes (or a subset thereof, as controlled by the coupling service) arrive. Note, as well, that

while a process may serve data both between and at synchronization points, it may only request data

between synchronization points.

Figure 6: Execution Sequence Diagram for the Coupling Service and Co-Simulation Participants

Details regarding processing between the Solution and Check Convergence synchronization points

are shown in Figure 7: Processing Details for the Coupling Service and Co-Simulation Participants (p. 43).

During this stage of the analysis, the coupling service controls the advancement of co-simulation parti-

cipants, or solvers, through two secondary synchronization points: Data Transfer and Solve, both

shown in light gray. The sequencing of solvers is controlled by manipulating the relative order in which

the solvers advance beyond these secondary synchronization points. For example, solvers with

identical sequence indices all advance through the Data Transfer synchronization point together, and

then do the same for the Solve synchronization point.



Figure 7: Processing Details for the Coupling Service and Co-Simulation Participants

These figures highlight that all participants traverse the duration of the entire coupling step during

each coupling iteration. They have complete freedom, however, to traverse the coupling step duration

in one or more ‘solver’ steps, each of which may include one or more solver iterations. If multiple

‘solver’ steps are used within one coupling step, then this is referred to as sub-stepping (or sub-cycling).

Review the participant systems’ documentation to see if sub-stepping occurs and is supported with

System Coupling.

Convergence Management

By default, the system coupling log file reports Root Mean Square (RMS) convergence for data transfers

for both the source and target side of the transfer. Convergence of the coupling step is evaluated at

the end of each coupling iteration. Coupling step convergence requires that:

• the target side RMS values have reached the convergence criteria that you specified in the input to the

system coupling setup, and

• that the minimum number of coupling iterations that you specified are met.

If the coupling step is not yet converged, then a new coupling iteration is started. If the coupling step

is converged, then a new coupling step is started if the coupling duration has not yet been reached.

Evaluating Convergence of Data Transfers

To evaluate convergence of data transfers, each iteration is measured against the previous iteration.

The change in all of the data transfer values between these two successive iterations is reduced to a

normalized value. When two successive iterations produce a normalized value that is under the conver-

gence target (you can change this convergence target, the default value is 1e-2), the data transferred

is converged.



Coupling Management

Two global (that is, over all locations) measures of convergence are evaluated and reported during ex-

ecution of the coupled analysis. These include the maximum and Root Mean Square (RMS) of the nor-

malized change in data transfer values. The RMS is the default measure used to determine convergence.

The measure can be changed to the maximum of the normalized value through the System Coupling

Input file.

The RMS value is evaluated as:

(1)µ=

� �

�

where ¶

� is the normalized change in the data transfer value between successive iterations within/across

a given coupling step, and is measured as:

(2)µ

=× − +

��

� � ��

�

where � is the data transfer value, and l is the location of the data transfer on the coupling interface.

In Equation 2 (p. 44), the denominator, or normalization factor, is evaluated differently in the transient

and general coupling analyses. In the transient coupling case, the normalization factor equals the average

of the range and mean of the magnitude of data transfer values over all locations for the current iteration.

In the general coupling case, it equals the average of the range and mean of the magnitude of data

transfer values over all locations for all iterations in the entire analysis. This normalization factor is a

representative scale for the data transfer values and ensures that division by zero (due either to zero

range or zero mean) is avoided.

In Equation 2 (p. 44), the numerator, �, is the un-normalized change between successive iterations,

and is expressed as:

(3)= −

� ��

��

�

��

where ��

�� and �

�

�� correspond to the current and the previous iterations respectively, and � is the

under-relaxation factor applied in forming the final value applied during the current iteration. In the

first coupling iteration of every coupling step,� is assumed to be unity.

When there is no change in data transfer values, the default for RMS/MAX is 1.0e-014.

Note

Global data transfer convergence measures are initialized to unity during the first

coupling iteration of the first coupling step. Although monotonic convergence to the

specified target values is ideal, oscillatory convergence and/or divergence (i.e., constant

or increasing convergence measures) may also occur.

Data Transfers

Data transfers in System Coupling use one of two data transfer algorithms:



• Profile Preserving data transfer algorithm is used when transferring non-conserved quantities like

displacements and temperatures.

• Conservative Profile Preserving data transfer is used when transferring conserved quantities like mass,

momentum, and energy flows (for example, forces).

These two data transfer algorithms are discussed in the section Data Transfer Algorithms (p. 46). Both

data transfer algorithms incorporate the following components:

• Data Pre-Processing: This is the first component used in the data transfer process and could involve

creation of supplemental data on mesh locations that are needed by the mapping and interpolation

algorithms.

• Mapping: This is the second component used in the data transfer process and involves the match-

ing/pairing of a source and a target location to generate weights. For example, in a fluid-solid inter-

action problem, a fluid node must be mapped to a solid element to receive displacements. Similarly,

either a solid node or a Gauss point in a solid element must be mapped to a fluid element to receive

stress.

• Interpolation: This is the third component used in the data transfer process and involves the (re)use

of the generated weights to project source data onto target locations.

• Interpolated Data Post-Processing: This is the final component of the data transfer process and

could involve explicit under-relaxation, ramping, and/or clipping of the target data, as well as the

creation of supplemental data on mesh locations needed by the consumers of interpolated, target

data.

Note that participant data transfer regions must consist of triangular or quadrilateral faces. Polyhedral

faces as well as faces with hanging nodes (cut-cells) are not supported by System Coupling.

A variety of algorithms exist in the literature to address these components. In the discussions below,

only those that are used in System Coupling are presented.

• Data Pre-Processing Algorithms (p. 45)

• Mapping Algorithms (p. 46)

• Interpolation Algorithms (p. 53)

• Interpolated Data Post-Processing Algorithms (p. 53)

Important

Unit conversions are automatically applied for all data transfer algorithms during each of the

mapping and interpolation phases.

Data Pre-Processing Algorithms

Data pre-processing algorithms are used to create supplemental data on mesh locations that are needed

for mapping and interpolation. These pre-processing algorithms may also be used during post-processing

of interpolated data to provide data on the mesh locations required by co-simulation participants.



Data Transfers

Creating Nodal Data from Face/Element Centroid Data

Conservative data (for example, heat flows and forces) may be available on element (face) centroids. If

these data are required on nodes, the following steps are executed:

• an element-node value is calculated by dividing the total value by the number of nodes that define the

element, and

• the element-node values are scattered to, and accumulated at, each node.

Creating Face/Element Data from Node Data

Conservative data (for example, heat flows and forces) may be available on nodes. If these data are re-

quired on elements/faces, the following steps are executed:

• the area for each face/element that shares a common node is calculated for all nodes,

• the nodal area is calculated as the sum of all areas for each face/element that shares a common node,

• the area fraction is calculated as the area divided by nodal area for each face/element that shares a

common node, and

• the face/element value is calculated for each element-node as the nodal value times the respective area

fraction.

The face/element values corresponding to each element-node are summed if a total face/element value

is required.

Mapping Algorithms

Several mapping algorithms are used when executing data transfers during system couplings. To assist

in evaluating the quality of the mapping, a mapping summary is included in the System Coupling service

log file (see System Coupling Service Log File (scLog.scl_, scLog_##.scl ) (p. 57)). Note that

summary data depends upon on the availability and relevance of specific information (for example, the

number of nodes or area on the surface and/or target meshes) for each mapping algorithm.

Mapping is performed only at the start of the System Coupling simulation. Because of this, the mesh

topology on the data transfer regions cannot change (that is, cannot be dynamically remeshed) during

the simulation.

The two mapping algorithms used in System Coupling (discussed below) are Bucket Surface and Gen-

eral Grid Interface (GGI).

Data Transfer Algorithms

Data transfer algorithms are combinations of mapping/interpolation algorithms (discussed in the sections

above) that are used in the System Coupling service.

Note that the fidelity of the data transferred to the target side of the interface is limited by the least-

resolved side of the interface. For example, if the target side of the interface is significantly coarser than

the source side, then only the large scale features of the source data will be captured in the data



transfer. Similarly, if the target side of the interface is significantly finer than the source side, then the

resulting target data will be a linearly interpolated representation of the data on the source side.

Note

A number of advanced controls for the data transfer algorithms are exposed via expert

settings. For more information, see Expert Settings Related to Mapping in Expert

Settings (p. 24).

Profile Preserving

The Profile Preserving data transfer algorithm is the default algorithm used by System Coupling when

transferring non-conserved quantities like displacements and temperatures. For this data transfer al-

gorithm, the Bucket Surface mapping algorithm is used to generate mapping weights. In this algorithm,

the mesh nodes on the target side of the data transfer interface are mapped onto mesh elements on

the source side as illustrated in Figure 8: Mapping target node to source element for Profile Preserving

Data Transfer (p. 47). Standard, weight-based interpolation (resulting in the � � values shown) and sub-

sequent under-relaxation are used to evaluate the final data applied on the target side of the interface.

Figure 8: Mapping target node to source element for Profile Preserving Data Transfer

Profile Preserving data transfer algorithm is the default algorithm used when transferring non-conser-

vative quantities because of the profile-preserving nature of the mapping weights generated by the

Bucket Surface algorithm.

Conservative Profile Preserving

The Conservative Profile Preserving data transfer algorithm is the default algorithm used by System

Coupling when transferring conserved quantities like mass, momentum, and energy flows (for example,

forces). For this data transfer algorithm, the General Grid Interface (GGI) mapping algorithm is used to

generate mapping weights. Standard, weight-based interpolation and subsequent under-relaxation are

used to evaluate the final data applied on the target side of the interface.

Conservative Profile Preserving data transfer algorithm is the default algorithm used when transferring

conserved quantities because of the conservative nature of the mapping weights generated by the GGI

algorithm. Resulting target values are locally (in the vicinity of each source and target element) conser-

vative. If the source side of the interface is completely mapped to the target side of the interface, then

the resulting target values are also globally conservative. If any portions of the source side of the interface

are not mapped onto the target side, then the data transfer is not globally conservative. Note that any

portions of the target side of the interface that are unmapped (that is, weights equal to zero) are

automatically assigned a value of zero, which differs from the handling of unmapped nodes using the

Profile Preserving data transfer algorithm.



Data Transfers

Bucket Surface

The underlying ideas for this algorithm are presented in the book Computational Nonlinear Mechanics

in Aerospace Engineering, American Institute of Aeronautics and Astronautics, edited by S. Atluri, ISBN

1563470446, Chapter 5, Fast Projection Algorithm for Unstructured Meshes by K. Jansen, F. Shakib, and T.

Hughes, 1992. Specifically, the implementation of the Smart Bucket Algorithm as described in the chapter

stated above is used in system coupling. This algorithm generates weights that are ideal for transferring

the profiles of non-conserved quantities like stresses, displacement, temperature, and heat transfer

coefficient from a source mesh to a target mesh. Since a complete description of the algorithm is

available in the reference quoted above, only a brief overview of it is presented below.

The first step in the process of computing the mapping weights using the Smart Bucket Algorithm is

to divide the mapping source mesh into an imaginary structured grid, with each grid section called a

“bucket.” A 2D bucket is used to demonstrate this concept in Figure 9: Example of a Bucket Grid on a

2D Source Mesh (p. 48). Similarly, a 3D bucket grid is generated for a 3D mesh, and this is what is used

in System Coupling.

Next, each node on the data transfer regions of the target mesh is initially associated with a bucket. In

System Coupling, data transfer regions consist of element faces from the 3D mesh. Two cases arise:

buckets associated with the target node are either empty (without even one source element in it) or

non-empty. For example, bucket A shown in Figure 9: Example of a Bucket Grid on a 2D Source

Mesh (p. 48) is empty. Each case (empty and non-empty buckets) is discussed separately in the sections

below.

Figure 9: Example of a Bucket Grid on a 2D Source Mesh

Case 1: The bucket associated with a target node is non-empty

If the bucket associated to a given target node is non-empty, the mapping algorithm attempts to match

each of the target nodes to one source element in the bucket.



First, each target node is checked to see if it is in the domain of any of the source elements. This is

done by looping through all the source elements in that bucket and checking to see if the target node

is within their domain. For each source element in the bucket, the vector element–local (or natural)

coordinates � (corresponding to the vector of global coordinates of the target node,µ� ) is found

by solving the set of nonlinear equations given by the isoparametric mapping below:

(4)µ =� � � ��

��

where � �

is the matrix of linear shape functions associated with the source element and ��

is the vector of global coordinates of element–local node �. It is then checked to see if � lies within

the domain of the source element based on certain criteria discussed next.

For a four-noded quadrilateral source element, if the natural coordinates � corresponding to a target

node satisfy the conditions in Equation 5 (p. 49) below, the target node is said to be exactly within the

domain of the element.

(5)≤≤

�

�

�

�

where �� and �� are the components of the vector of natural coordinates �. However, if the natural

coordinates do not satisfy the conditions in Equation 5 (p. 49) but do satisfy the ones in Equation 6 (p. 49)

below, then the target node is in the domain of the source element but only within the specified toler-

ance �� (also known as element edge tolerance). The value of tolerance is exposed in the System

Coupling UI as one of the expert settings. See the description of ProfMapEdgeTol in the section

Expert Settings Related to Mapping in Expert Settings (p. 24).

(6)≤ +≤ +

� ��

� ��

!

This concept is explained with the help of Figure 10: A Quadrilateral Source Element in the Natural Co-

ordinate Space (p. 50) wherein a quadrilateral source element is shown along with two different target

nodes, one of which satisfies Equation 5 (p. 49), and other that satisfies Equation 6 (p. 49).



Data Transfers

Figure 10: A Quadrilateral Source Element in the Natural Coordinate Space

Similarly, for a three-noded triangle element, the conditions listed in Equation 7 (p. 50) below, are used

to check if a target node is exactly within the domain of the element:

(7)

≥≥

− − ≥

�

�

� �

�

�

� �

And the conditions in Equation 8 (p. 50) below will determine if the target node is within the domain

but up to a tolerance ��.

(8)

≥ −≥ −

− − ≥ −

� ��

� ��

� � ��

�

�

Now that target nodes are determined to be in the domain of specific source elements, each node must

be paired with only one source element. In both of the cases above (four-noded quadrilateral and three-

noded triangle), it is possible that a target node occurs (either exactly or within a tolerance) in more

than one source element’s domain. The finite element interpolation of the nodal solution requires each

target node to be paired with only one source element.

To satisfy this requirement, the target node is consequently paired with that source element for which

the gap is minimized. The gap is defined as the Euclidean distance between the target node and its

projection onto/into a source element. In some cases, such as when candidate source elements are co-

planar, the gap values may be identical and an alternate approach is required to pair the target node

with one source element. Under these conditions, only the source elements with identical (and minimized)



gaps are considered. The target node may be exactly in the domain of any of these source element, or

it will be in their domain within a tolerance. Preference is given to the last source element for which

the target node is exactly in its domain. If the target node is only in the different domains within a

tolerance, then the last candidate source element is used.

Once the target node is paired with a source element, mapping weights are computed by evaluating

the finite element shape functions associated with the paired source element at the target node.

If no target node-to-source element match is found in a non-empty bucket, then the target node is re-

ported as being unmapped. It is important to note, however, that mapping weights are still evaluated

for such nodes using the Bucket Surface Algorithm. Specifically, all unmapped target nodes are simply

mapped to the nearest source node in the bucket and the target node is assigned the solution value

corresponding to that source node.

Note

Significant ‘gap’ distances between successfully-mapped target nodes and source elements

may occur. For information about how to have mapped nodes with ‘gap’ distances larger

than a specified tolerance be reported as unmapped, see Expert Settings Related to Mapping

in Expert Settings (p. 24).

Case 2: The bucket associated with a target node is empty

If the bucket initially found for the target node is empty, then the closest non-empty bucket is found

and the same procedure as highlighted in Case 1 is followed so that each target node is mapped to

one source element and mapping weights are calculated.

Unmapped Nodes

With the Bucket Surface algorithm, there are two types of target nodes that can be reported as un-

mapped: nodes that do not fall within a bucket (these are “unmatched nodes”), and nodes that do fall

within a bucket, but that do not meet the gap tolerance (these are "gap nodes”). Unmatched nodes

are mapped to the nearest source node in the bucket and the target node is simply assigned the solution

value corresponding to that source node. Unmatched nodes are always reported as unmapped in the

SCL file. Gap nodes are within a bucket, and so are mapped to the source nodes like all of the other

mapped nodes and given a value accordingly. Gap nodes are reported as mapped in the SCI file. The

gap tolerance and the reporting of gap nodes in the SCI file can be modified using Expert Settings (p. 24).

General Grid Interface (GGI)

The underlying ideas for this algorithm are presented in the article on Three- Dimensional Navier Stokes

Predictions of Steady-State Rotor/Stator Interaction with Pitch Change, 3rd Annual Conference of the CFD,

Society of Canada, Banff, Alberta, Canada, Advanced Scientific Computing Ltd, by P.F. Galpin, R.B. Broberg

and B.R. Hutchinson, June 25-27, 1995. This algorithm generates weights that are ideal for transferring

conserved quantities such as mass, momentum and energy flows.

In this algorithm, each element face on both the source and the target sides is first divided into n integ-

ration point (IP) (sub-) faces, where n is the number of nodes on the face. The three-dimensional IP

faces are then converted into a two-dimensional quadrilaterals made up of rows and columns of pixels.

Pixels from the converted quadrilaterals on the source and target sides are intersected, creating a

number of overlapped areas called ‘control surfaces.’ Mapping weight contributions are evaluated for

each control surface based upon the associated source and target element face areas and the pixel in-



Data Transfers

tersections. Final mapping weights for each of the target (or source) nodes are evaluated by accumulating

these control surface contributions.

If no control surfaces are created (for example, when no polygon intersection between mapping source

and target exists), then mapping weights are identically zero and nodes and elements on the target (or

source) side of the interface are reported as being unmapped.

As an example, consider the schematic shown in Figure 11: General Grid Interface Mapping (p. 52) that

corresponds to a typical interface between the source (sending) and target (receiving) sides. In the

schematic, the control surfaces resulting from the intersection of all IP faces on the interface (labeled

with an ‘X’), are shown. For example, the IP faces S1 and S2 on the source side intersect with the IP

faces R1 and R2 on the target side creating areas A1, A2, and A3 on the control surface. In this case,

the mapping weight contributions for the target IP face R1 (and associated target node) that are asso-

ciated with the source IP faces S1 and S2 (and nodes) are respectively given by:

(9)=��

��

�

�

and

(10)=+

��

� ��

�

� �

Figure 11: General Grid Interface Mapping



Interpolation Algorithms

The interpolation algorithm is responsible for providing target node values using the source data and

mapping weights that were generated by the mapping algorithm(s) (see Mapping Algorithms (p. 46)).

The mapping weights are applied in Equation 11 (p. 53) to evaluate �, which is the target node, or iter-

ation point (IP) face value.

(11)∑==

� � ��

�

� ��

where �� is the value at the �

source node, and �� is the associated weight. For weights obtained

with the bucket surface mapping algorithm, is the number of nodes in the source element. For weights

obtained via the GGI mapping algorithm, � is the number of areas (associated with a target IP face)

obtained due to the intersection of the sender and receiver faces on the control surface.

Interpolated Data Post-Processing Algorithms

Interpolated data post-processing algorithms are the last step in the data transfer process. In many

situations (such as an implicit coupling where the number of coupling iterations within a coupling step

is more than one), the interpolated target data needs to be post-processed before it is exposed to the

target participant of the data transfer. Two optional post-processing algorithms may be applied to the

target data generated during interpolation: ramping and under-relaxation. Each of these algorithms is

used to improve convergence of the overall analysis. Other post-processing algorithms that are auto-

matically applied involve:

• clipping unphysical data values (p. 55), and

• creation of supplemental data on mesh. For information on the creation of supplemental data, see

Data Pre-Processing Algorithms (p. 45).

Unless otherwise noted, post-processing algorithms are applied to each:

• data transfer location (node), and

• component of vector data transfers

Ramping Algorithm

The ramping controlled by the System Coupling service works by slowing the application of the source-

side value on the target-side of the data transfer. For each data transfer location (node) where ≤� ��

is true, the following formula is applied:

(12)= + −� ��

��

�� !�"#� ��$ �� !�"#�

where

%&'()*+

is the ramped, target-side value.

,-./.0.12.

is the reference target-side value, which for the first coupling step is the initial

value for the data transfer variable (see Table 3: Initial Values used for the Reference

Target-Side Value (p. 54)). Thereafter, the reference target-side value is the final value



Data Transfers

from the previous coupling step. The one exception is displacement, where for every

coupling step, ��

is always .

��

is the raw, target-side value obtained from interpolation.

� is the current coupling iteration number within the coupling step.

� �� is the minimum number of coupling iterations per coupling step.

Under-Relaxation Algorithm

Under-relaxation works by limiting a potentially large variation of the target-side data between two

successive coupling iterations. For each data transfer location (node), the following formula is applied:

(13)= + −� � � � ��

where

�� !"�#

is the relaxed, target-side value.

$%&'&(&)*&

is the reference target-side value. For coupling iterations within a coupling

step, the reference target-side value is the final value from the last coupling iteration.

For the first coupling iteration of the first coupling step, the reference target-side value

is the initial value for the data transfer variable (see Table 3: Initial Values used for the

Reference Target-Side Value (p. 54)). For the first coupling iteration of all subsequent

steps, the reference target-side value is the final value from the last coupling step.

+,-.

is the raw, target-side value obtained from interpolation or from ramping (if applied).

Note that if you have applied both ramping and under-relaxation, the data is first ramped

and then under-relaxed. In this case, =/ /012 013456

for the under-relaxation’s raw

target-side value.

ω is the under-relaxation factor (URF). In a transient analysis, in the first coupling iteration

of every coupling step, the URF is overridden and set to 1, and so data transferred at

this coupling iteration is not under-relaxed.

Initial Values used in Ramping and Under-Relaxation Algorithms

The default for the initial value used as the reference target-side value (789:9;9<=9

) in Equation 12 (p. 53)

and Equation 13 (p. 54) is based on the physical type of the variable. The default values are listed in

Table 3: Initial Values used for the Reference Target-Side Value (p. 54).

Table 3: Initial Values used for the Reference Target-Side Value

NotesInitial Value used for the

Reference Target-Side

Value (>?@A@B@CD@

)

Variable

Type

For the ramping algorithm,

the reference target-side

0.0 [m]Incremental

displacement

value for incremental displace-

ment is always 0.0 [m] for

every coupling step.

0.0 [N]Force



NotesInitial Value used for the

Reference Target-Side

Value (��

)

Variable

Type

Variables of this type include

temperature and near wall

temperature.

295.15 [K]Temperature

0.0 [W]Heat Rate

0.0 [− −

��

]Heat Transfer

Coefficient

These defaults for the initial values above can be overridden using the methods discussed in the section

Expert Settings (p. 24). Note that for the ramping algorithm, the reference target-side value for displace-

ment cannot be modified using expert settings.

Clipping Algorithm

Although uncommon, it is possible that unphysical values, such as negative heat transfer coefficients,

are provided by the data transfer source or are generated during mapping. To ensure unphysical values

are not applied to the data transfer target, these unphysical values are clipped to be within a valid

range. For example, any negative heat transfer coefficient values are changed to 0 [− −

� ��

] before

being transferred to the target participant.

The variable(s) that are clipped and their valid range are listed in the table below. Note that at the end

of any coupling step where clipping is used, the System Coupling Log file will have a message about

the clipping.

Maximum ValueMinimum ValueVariable

Type

unlimited0 [

− −��

� �]

Heat Transfer

Coefficient


This section outlines the files used by the coupling service during its execution.

System Coupling Service Input File (scInput.sci)

System Coupling Service Shutdown File (scStop.stop)

System Coupling Service Input File (scInput.sci)

The scInput.sci file, which is an XML file generated by the System Coupling system in Workbench,

provides analysis-related inputs to the coupling service. The input XML file is composed of several dif-

ferent sections: participants, analysis, transfers, and execution control. You can modify this file, with an

appropriate XML editor, although this is not encouraged.

When the System Coupling system's Setup cell is up-to-date and the System Coupling user interface is

active (by editing either the System Coupling Setup or Solution cell), you will be able to export, and

save, the input file using the Export SCI File option available from the Workbench File menu.

For more detailed information about the input file contents, see Understanding the System Coupling

Input File (p. 58).




System Coupling Service Shutdown File (scStop.stop)

If a text file named scStop.stop is found in the coupling service’s run directory, then the service will

shut down as soon as possible. The shutdown file should contain two (or more) lines as shown below:

0The reason for terminating the analysis

The first line contains an integer flag that indicates whether or not the termination should be interpreted

as an ‘interrupt’ or as a ‘stop’.

• With an integer value of 0, the analysis will be interrupted; the coupling service will complete the current

coupling step and signal the co-simulation participants that the execution has ended. This will cause the

coupling service and participants to shutdown cleanly.

• With an integer value of 1, the analysis will be stopped; the coupling service will signal the co-simulation

participants to abort the run as quickly as possible. This will not produce a clean shutdown.

The second and subsequent lines in the file are reported in the coupling service’s log file when summar-

izing the reason for shutting down the coupled analysis.


This section outlines the files generated by the coupling service during its execution.

System Coupling Server File (scServer.scs)

System Coupling Service Log File (scLog.scl_, scLog_##.scl)

System Coupling Results File (scResults_##_######.scr)

System Coupling Server File (scServer.scs)

The scServer.scs file, which is written to the service’s run directory, contains information that is

used to connect the participants to the coupling service. This file is generated shortly after the coupling

service is started, and indicates that the coupling service is ready to receive connections from the co-

simulation coupling participants.

This text file contains the following lines of data:

• The server’s port and host, separated by an ‘@’ character.

• A block containing the number of co-simulation participants connected to the System Coupling system

in the Workbench schematic, and their unique and display names. In the Workbench environment:

– the unique names are automatically generated and are reported as the ComponentID in the

Properties view of the co-simulation participant’s Solution cell,

– the display names correspond to the names (which you are able to specify) below the participant’s

system

Example 1: An Example scServer.scs File

[email protected]

2

Solution 1

Fluid Model



Solution 2

Solid Model

Note

When the participants are started and instructed to connect to the running SC Service, they

must connect to the service using the unique names (for example Solution 1 and

Solution 2 in the example above).

System Coupling Service Log File (scLog.scl_, scLog_##.scl)

The scLog.scl file provides key runtime information related to a coupled analysis between various

participants, including:

• The command line used to start the system coupling service

• System coupling header and build information

• A summary of system coupling setup information, including:

– Analysis information

– Coupling participant information (number of participants, and summary information pertaining to

each participant)

– Data transfer information (number of data transfers, and summary information pertaining to each

data transfer)

– Execution control information (co-simulation sequence, debug output)

– Setup validation (summary of system coupling input file validation)

– System coupling co-simulation summary (summary of system coupling participants)

• Solution information, including:

– Mapping summary (including percentages of mapped source and target nodes and the percentages

of mapped source and target areas, depending upon the mapping algorithm that was used)

– Convergence information at each coupling step and iteration

The information here includes the coupling step index, the current analysis time for transient

couplings, the coupling iteration index, the participant name and data transfer name, the

participant convergence status (for example, “Not Yet Converged...”, “Converged”, and so on),

and the data transfer convergence (for example, the RMS/Maximum normalized change).

• Shutdown information, including:

– Run completion status

During the execution of a run, the service log file, named scLog.scl_ , is generated, evolving with

the analysis, and is finally renamed at the end of the run. The final log file is named with the convention:




scLog_##.scl , where the suffix _## denotes the run index. For example, scLog_13.scl corresponds

to the 13th run (that is, the 12th restart) executed for the analysis.

For more detailed information about the log file contents, see Understanding the System Coupling Log

File (p. 65).

System Coupling Results File (scResults_##_######.scr)

The system coupling results file contains important data generated and used by the system coupling

service during the analysis. This data enable you to:

• Restart the analysis or continue from a previous analysis

• Post-process the heavy weight interface data

• Monitor the analysis’ convergence

• Reconstruct the analysis

The specific data contained in the file are summarized as:

• A history of the input (SCI) files used to drive the coupling service’s execution

• Convergence data corresponding to the data transfers and solvers’ field equations

• Heavyweight data corresponding to the source and target regions and variables for defined data transfers

A system coupling results file is always created at the end of the analysis. The default file naming con-

vention is of the form scResults_##_######.scr , where the run index is recorded in the “_##”

suffix and the coupling step index is recorded in the “_######” suffix (for example, scRes-

ult_13_000101.scr corresponds to the 101st

coupling step within the 13th

run of the analysis). In-

termediate results files, with the same naming convention, can also be created at various coupling step

intervals (defined by you) during the analysis.

Important

All data stored in the System Coupling Result file(s) are written in the SI unit system.


The input XML file is composed of several different sections: participants, analysis, transfers, and execution

control.

The participant section contains information obtained through the coupling data interface (CDI) and

the connections to upstream solver systems. It is intended to be read-only. In the participants section,

you can view the Count (an integer representing the number of connected participants). For each

connected participant, you can view the following: Note that depending upon the type of participant

(co-simulation or static data), some of the options may or may not be applicable.

• Type (integer attribute)

The type of coupling participant (0 – co-simulation, 1 – static data)



• Name (string)

The name of the participant. This is the name with which the participant identifies itself to the system

coupling. This corresponds to the “Component ID” which is unique to a specific system’s Solution

cell in the Workbench user interface.

• DisplayName (wide string)

The display name of the participant provided by you in the in Workbench user interface.

• FilePath (string)

The full path to the primary file used to access source data from a static data participant.

• SupportsCouplingIterations (boolean)

Whether or not the co-simulation participant supports the execution of multiple coupling iterations

per coupling step.

• UnitSystem

• Regions (options below are applicable to an individual region)

– Name (string)

The name of the region (intrinsic to the participant).

– DisplayName (wide string)

The display name of the region given by you in the Workbench user interface.

– TopologicalDimensionality (integer)

The geometry type of the region (0 – undefined, 1 – point, 2 – curve, 3 – surface, 4 – volume).

• Variables (options below are applicable to an individual variable)

– Name (string)

The name of the variable (intrinsic to the participant).

– DisplayName (wide string)

The display name of the variable given by you in the Workbench user interface.

– PhysicalType (string)

The physical type of the variable (options include: Length / Force).

• BaseUnits (strings denoting base units for all data of noted physical type)

– Length (string)

– Time (string)

– Mass (string)




– Luminance (string)

– Angle (string)

– SolidAngle (string)

– Temperature (string)

– ChemicalAmount (string)

– Current (string)

The analysis section contains details used to define the coupled analysis. In the analysis section, you

can set the following:

• AnalysisType (integer)

This setting defines the nature of the sequential steps used in coupling co-simulation participants.

Available option is 0 (general), and 1 (transient).

• Initialization

This setting defines the initial time for the coupled analysis

– Option (integer)

Available options are 0 (Program Controlled) and 1 (Start Time). The former is the default option

for coupling initialization. When this option is used, the coupling service will make the most appro-

priate choice of an initial time value. When the latter option is used, the coupling service will

override the initial/start time for the analysis with the value specified as part of Time (see below).

– Time (double)

If option 1 is chosen above, then this is the initial time for the coupling analysis.

• Duration

This setting defines the duration of the coupled analysis.


Available options are 0 (NumberOfSteps ) and 1 (EndTime ).

– NumberOfSteps (integer)

This option is available only if no end-time requirements exist for co-simulation participants.

– Time (double)

Final time of coupling analysis.

• Step

– MaximumIterations (integer)

The maximum number of coupling iterations allowed per coupling step.



– MinimumIterations (integer)

The minimum number of coupling iterations allowed per coupling step.

– Size (double)

The size of the coupling step when it is associated with a time (this is done for transient analyses,

size is measured in seconds).


Available option is 1 (coupling step size, used for transient analyses) and 0 (non dimensional step

size, used for general analyses).

• UnitSystem (string)

The transfers section contains details used to define the data transfers between any static and co-sim-

ulation coupling participants. In the transfers section, you can set the Count (an integer representing

the total number of data transfers) as an attribute. For each coupling transfer, you can set the following:

• Name (string)

The name of the transfer (which you provided) in the Workbench user interface.

• ExecuteCouplingAt (integer)

This setting defines “when” the current data transfer is executed during the coupled analysis. The

only available option is 2 (Start of Iteration).

• Source

The information related to the source participant involved in the data transfer.

– Participant (string)

The name of the source participant.

– Region (string)

The name of the source region (defined for a given participant) participating in the data transfer.

– Variable (string)

The name of the source variable, the data corresponding to which is exchanged during the data

transfer (also defined for a given participant).

• Target

The information related to the target participant involved in the data transfer

– Participant (string)

The name of the target participant

– Region (string)




The name of the target region participating in the data transfer

– Variable (string)

The name of the target variable, the data corresponding to which is exchanged during the data

transfer

• ConvergenceOption (integer)

Specifies the type of data transfer convergence check in an implicit coupling (that is, if more than

one coupling iteration per coupling step is specified; a value of 0 indicates the RMS normalized

change).

• ConvergenceTarget (double)

The target value that determines the convergence of the data transfer

• UnderRelaxationFactor (double)

The Under Relaxation factor (URF) applied to the data increments between any two successive

coupling iterations. The URF has a range of < ≤ . Note that when transferring incremental

displacement, the URF must equal 1. In this case, a value less than 1 can lead to an accumulation of

errors, and the following warning will be displayed in your SCL file:

The under relaxation factor for the data transfer named '<name of data transfer>' is smallerthan one. Under relaxation factor less than one for incremental displacement might lead to errors.

• Ramping (integer)

This setting defines if and how ramping is used when applying data from the source-side to the target-

side of the data transfer. Valid options are: 0 – none (that is, stepped), and 1 – linearly ramped up to

the minimum number of coupling iterations. The default is none, which implies the target side of

the data transfer experiences the full value from the source side during the first coupling iteration.

The execution control section contains details used to define the solution sequence between the

coupling participants, the system coupling debug output, intermediate result files output, and expert

settings. For each participant, you can set the following:

• CoSimulationSequence

This subsection is used to specify the sequencing of co-simulation coupling participants (most often

solvers) during a coupling iteration. In the CoSimulationSequence subsection, the 'Count' attribute

specifies the number of participants for which sequencing information will be provided.

– Participant

A Participant subsection is required for each co-simulation participant.

→Name (string)

The name of the participant.

→SolutionSequence (integer)



The sequence number of the participant in the coupled solution. Within a coupling iteration, a

participant with a larger sequence number will solve later than another with a lower sequence

number.

• DebugOutput

This subsection is used to specify the section(s) of debug output to write to the system coupling log

(SCL) file. As presented below, the level of detail is specified for each section or all sections (the default).

– DefaultOutputLevel (integer)

This setting provides the default level for the different sections of debug output. If this entry is set

and another specific entry (for example, Startup) also exists, then the output level for the specific

entry will override the level set here.

– Startup (integer)

This setting controls the level of output from the start of the coupling service until creation of the

“Summary of SC Setup” banner in the SCL file.

– ParticipantConnection (integer)

This setting controls the level of output from the end of the setup validation until the “Initial Syn-

chronization” synchronization point.

– AnalysisInitialization (integer)

This setting controls the level of output from the “Analysis Initialization” until the “Solution” syn-

chronization point.

– SolutionInitialization (integer)

This setting controls the level of output during the setup of coupling steps and iterations. This

output does not include information related to the data transfers.

– ConvergenceChecks (integer)

This setting controls the level of output from the “Check Convergence” synchronization point until

the next synchronization point, which may be either “Shutdown” or “Solution.”

– Shutdown (integer)

This setting controls the level of output after the “Shutdown” synchronization point.

– Transfers

This section is used to specify the debug output generated for data transfers. Note that header

information for mapping is generated whenever the mesh coordinate or mesh topology output is

requested. Similarly, header information for the data transfers is generated whenever the transfer

data output is requested.

→DefaultOutputLevel (integer)

This setting provides the default level for the different kinds of debug output. If this entry is set

and another specific entry (for example, SourceMeshCoords ) also exists, then the output level

for the specific entry will override the level set here.




→SourceMeshCoords (integer)

This setting controls the level of output for mesh coordinates of the source region in all data

transfers.

→SourceMeshTopol (integer)

This setting controls the level of output for mesh topology (elements and nodes) of the source

region in all data transfers.

→SourceData (integer)

This setting controls the level of output for the source data in all data transfers.

→TargetMeshCoords (integer)

This setting controls the level of output for mesh coordinates of the source region in all data

transfers.

→TargetMeshTopol (integer)

This setting controls the level of output for mesh topology (elements and nodes) of the source

region in all data transfers.

→TargetData (integer)

This setting controls the level of output for the target data in all data transfers.

The level of detail to include in debug output is controlled using one of the following integer values

for either the default or specific sections of output:

– 0: None

– 1: Level 1

– 2: Level 2

– 3: Level 3

– 4: Level 4

– 5: All Levels

Increasing values always generate more detailed output. Note, as well, that the output level settings

for each of the mesh coordinates and topology, and transfer data control the number of lines of

output generated. Specifically, 10L lines of data will be written for an output level setting of L (for

example, 100 lines will be written for an output level of 2, or “Level 2”).

• IntermediateResultsFileOutput

This subsection is used to specify the frequency at which intermediate result files, which can be used

for restarts, are written by the System Coupling service.

– FrequencyOption (integer)



Available options are 0 (every coupling step) and 1 (coupling step interval)

– StepInterval (integer)

The coupling step interval at which intermediate result files should be generated (Note that this

is valid only when FrequencyOption is set to Step Interval). For example, using a step interval

of 3, results will be generated at steps 3, 6, 9, ...

The following entry may be reported in the SCI file, but is not used by the System Coupling service:

• MappingSettings


The System Coupling Service log file (scLog.scl ) provides key run time information and is divided

into four blocks:

• start-up and executable information,

• coupled analysis setup information,

• solution details,

• and shut-down information.

The start time and date, command line information and executable details for the run appear as follows:

Run start time and date: 10:15:41, Sep 19 2013

Command line used to start this service:

C:\Program Files\ANSYS Inc\v150\aisol\bin\winx64\Ansys.Services.SystemCoupling.exe -inputFile scInput.sci

==================================================================================================================================================================================================================| || ANSYS System Coupling Service || Version 15.0, Copyright 2013 || (Build Info. - 10:09:03, Sep 19 2013) || |==================================================================================================================================================================================================================

The command used to start the System Coupling service is given next as shown below:

Command line used to start this service: C:\Program Files\ANSYS Inc (Dev)\v150\aisol\bin\winx64\Ansys.Services.SystemCoupling.exe

An echo of the SC service input file is provided next in the log file below the following header:

====================================================================== ====================================================================== | | | Summary of System Coupling Setup | | | ====================================================================== ======================================================================

The information generally found in this section includes unit system data (for example, MKS, and so

on), as well as information relating to coupling (time versus coupling step), initialization (options such




as time value or initial coupling step), duration (for example, end time), and step size and the maxim-

um/minimum number of iterations.

Note

When the coupling is defined by coupling step (and not by time), then time-related inform-

ation (initial time, end time, or step size) is not displayed in this section of the log file, and

only step-related information is available (for example, initial step, number of steps, maximum

and minimum iterations).

Summary of System Coupling Setup

Under this section of the log file, there are sub-blocks (for example, “Analysis Information”, “Coupling

Participant Information”, “Data Transfer Information”, “Execution Control Information”, “Setup Validation“

and “System Coupling Co-Simulation Summary”). A brief description of these sub-blocks is provided

below.

The Analysis Information section includes basic information about the coupling definition, the unit

system, as well as time and step information.

======================================================================| Analysis Information |======================================================================

General : Analysis Type = Transient Unit System = MKS

Initialization : Option = Automatic

Step : Option = Step Size Size = 0.05 Minimum Iterations = 5 Minimum Iterations = 5

Duration : Option = End Time Time = 0.05

The Coupling Participant Information section includes information about each of the solvers connected

to the system coupling simulations (for example, internal name, type (either Co-Simulation or Static

Data), units, and so on). Additional information for coupled regions and variables that appear in data

transfers is also displayed in this section of the log file. This additional information includes: the coupled

name and type (for regions); and the variable name and physical type (for variables). This information

is not displayed for regions and/or variables that do not participate in data transfers. If such regions or

variables exist, a message is written to indicate that the related information has been omitted from this

section of the log file.

======================================================================| Coupling Participant Information (2) |======================================================================

+--------------------------------------------------------------------+| Participant: Fluent |+--------------------------------------------------------------------+

General : Unit System = MKS_STANDARD Type = CoSimulation Name = Fluent



Summary of Coupling Regions (1)Region : plate Internal Name = plate Type = Surface

Summary of Coupling Variables (2)Variable : Displacement Display Name Internal Name = INCD Physical Type = Length Variable : Force Display Name Internal Name = FORC Physical Type = Force

Summary of Base Units (9) Angle = radian ChemicalAmount = mol Current = A Length = m Luminance = cd Mass = kg SolidAngle = sr Temperature = C Time = s +--------------------------------------------------------------------+ | Participant: External Data | +--------------------------------------------------------------------+

General : Unit System = SI Type = Static Data Name = Setup 2 File Path = external_load_data.xml

Summary of Coupling Regions (1) Region : File1 Internal Name = ExtDataReg_Setup 2_0 Type = Surface

Summary of Coupling Variables (1) Variable : Temperature1 Internal Name = ExtDataVar_Setup 2_0_1 Physical Type = Temperature

Summary above omits variables not used in data transfers.

Summary of Base Units (9) Angle = radian ChemicalAmount = mol Current = A Length = m Luminance = cd Mass = kg SolidAngle = sr Temperature = K Time = s

The Data Transfer Information section includes:

• Region and variable information for the source and target of each data transfer

• Data transfer options, such as the convergence criteria and target

• The under-relaxation factor

• Ramping option

======================================================================| Data Transfer Information (2) |======================================================================




+--------------------------------------------------------------------+| Data Transfer: Mechanical Displacement to Fluent |+--------------------------------------------------------------------+

Source : Mechanical Region = Mechanical Wall Display Name Variable = DISP Display Name

Target : Fluent Region = plate Variable = Displacement Display Name

General Information : Name = Mechanical Displacement to Fluent Execute Transfer At = Start Of Iteration Convergence Option = RMS Change In Data Target Value = 0.01 Under Relax. Factor = 0.25 Ramping = None

+--------------------------------------------------------------------+| Data Transfer: Fluent Force to Mechanical |+--------------------------------------------------------------------+

Source : Fluent Region = plate Variable = Force Display Name

Target : Mechanical Region = Mechanical Wall Display Name Variable = FORC Display Name

General Information : Name = Fluent Force to Mechanical Execute Transfer At = Start Of Iteration Convergence Option = RMS Change In Data Target Value = 0.01 Under Relax. Factor = 0.25 Ramping = Linear to Min. Iterations

The Execution Control Information section includes a summary of the sequencing of co-simulation

participants, and requests for debug and intermediate result file output. Note that the debug and inter-

mediate result output summaries are generated only if such output is requested. For example:

======================================================================| Execution Control Information |======================================================================

+--------------------------------------------------------------------+| Co-Simulation Sequence |+--------------------------------------------------------------------+

Sequence Index : 1 Fluent Solver

Sequence Index : 2 Mechanical Solver

+--------------------------------------------------------------------+| Debug Output |+--------------------------------------------------------------------+

General Output : Default = Level 1 Startup = None Participant Conn. = None Analysis Init. = None Solution Init. = None Convergence Checks = None Shutdown = None



Data Transfer Output : Default = Level 1 Source Coords. = None Source Topology = None Source Data = None Target Coords. = None Target Topology = None Target Data = None

+--------------------------------------------------------------------+| Intermediate Restart Data Output |+--------------------------------------------------------------------+

Output Frequency : Option = Step Interval Interval = 3

The Setup Validation section includes any warning or error messages that may have been generated.

For example:

======================================================================| Setup Validation |======================================================================

+--------------------------------------------------------------------+| Warnings ( 1) |+--------------------------------------------------------------------+

1 ) Auto-Correction: The specified maximum iterations per step is less than the specified minimum iterations. The maximum iterations will be set to the minimum iterations.

+--------------------------------------------------------------------+| Errors ( 1) |+--------------------------------------------------------------------+

1 ) The solution sequence specified for the participant named 'Fluent' is not greater than zero. Adjust this (and other) sequence values appropriately.

The System Coupling CoSimulation Summary section includes a brief summary of the participants in

the co-simulation.

======================================================================| System Coupling CoSimulation Summary |======================================================================

Participant : Mechanical APDL Version/Build Info = Mechanical APDL Release 15.0 UP20130905 DISTRIBUTED WINDOWS x64 Version Participant : Fluent Version/Build Info = ANSYS Fluent 15.0.0

Solution

Next is the “Solution” block. Under it, the following information is provided.

====================================================================== ====================================================================== | | | Solution | | | ====================================================================== ======================================================================

The Solution block contains a Mapping Summary section:




+--------------------------------------------------------------------+ | MAPPING SUMMARY | +--------------------------------------------------------------------+ | Data Transfer | | | Diagnostic | Source Side | Target Side | +----------------------------------+----------------+----------------+ | Mechanical Displacement to Fluent| | | | Percent Nodes Mapped | N/A | 100 | | Fluent Force to Mechanical | | | | Percent Nodes Mapped | 100 | 100 | | Percent Area Mapped | 100 | 100 | +----------------------------------+----------------+----------------+

The current coupling step number and the current simulation time are reported as shown below. This

information will be a part of a box that is repeated in the log file at the beginning of every coupling

step. It looks similar to the following:

+====================================================================+| COUPLING STEP = 1 SIMULATION TIME = 0.001 ||--------------------------------------------------------------------|| Solver | Solution Status || Data Transfer | || Diagnostics | Source Side Target Side |+====================================================================+

Note that if the simulation is defined only by steps (and not by time), then the log file output will only

present step-related information.

Next is another box that repeats every coupling iteration of every coupling step. It looks like:

+--------------------------------------------------------------------+| COUPLING ITERATION = 1 |+--------------------------------------------------------------------+| Fluent | Not yet converged... ||- - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - || Mechanical Displacement to Fluent| Not yet converged... || Change:RMS | 1.00000e+000 1.00000e+000 ||--------------------------------------------------------------------|| Mechanical | Not yet converged... ||- - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - || Fluent Force to Mechanical | Not yet converged... || Change:RMS | 1.00000e+000 1.00000e+000 |+--------------------------------------------------------------------+| COUPLING ITERATION = 2 |+--------------------------------------------------------------------+| Fluent | Converged ||- - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - || Mechanical Displacement to Fluent| Converged || Change:RMS | 2.82982e-005 1.42982e-004 ||--------------------------------------------------------------------|| Mechanical | Converged ||- - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - || Fluent Force to Mechanical | Converged || Change:RMS | 1.30000e-004 2.08200e-000 |+--------------------------------------------------------------------+

As indicated above, after every coupling iteration, the convergence status is given for each participant.

Common participant status values are Converged and Not yet converged... , however, Diver-gence detected... and Status Unavailable could also be reported. Below the solver status

is a list of the data transfers for which the participant is the target, plus diagnostics used to evaluate

convergence of the data transfer. Any supplemental diagnostics (as described in the SC Log Output

Control Settings section in Understanding the System Coupling Input File (p. 58)) that have been re-

quested are also included here.

Notes specific to the execution of a given coupling step will be reported under the final coupling iteration

of the step. For example:



+====================================================================+ | NOTES | | * During this coupling step, the target variable, Convection | | Coefficient, was clipped for the data transfer: Upper HTC. | | * Intermediate result file written: scResult_01_000475.scr | +====================================================================+

Shutdown

Next is the “Shut Down” block under which the following information is included:

====================================================================== ====================================================================== | | | Shut Down | | | ====================================================================== ======================================================================

System Coupling Service shut down...

Run completed successfully.

The preceding output is generated under normal shutdown conditions. If a co-simulation participant

(or the coupling service itself ) fails during the analysis, the normal shutdown output will be replaced

by messages similar to the following:

+====================================================================+ | NOTICE | | An exception has occurred and has been transmitted to the coupling | | participants. These participants have been disconnected from the | | coupling service. | +====================================================================+

+====================================================================+ | System Coupling Exception | +====================================================================+ | Origin : Fluids Problem (Solution 1) | | Error Code : 2 | | Error Description : | | Fluent encountered fatal error after sync point Solve | +====================================================================+

System coupling run completed with errors.

The first block indicates that all co-simulation participants have been notified of the problem. The

second block indicates the origin (that is, the coupling participant) of the failure, and an error code and

description. For additional information, see Troubleshooting Two-Way Coupled Analyses Problems (p. 73).




Best Practice Guidelines for Using System Coupling

This chapter presents ideas to facilitate the successful setup and execution of a coupled analysis via

the System Coupling infrastructure:

Building up a Coupled Analysis from Decoupled Systems

Troubleshooting Two-Way Coupled Analyses Problems

Improving Coupled Analysis Stability

Building up a Coupled Analysis from Decoupled Systems

Coupling otherwise independent analysis systems often introduces additional non-linearity to the

solution and solution process. For this reason, it is strongly recommended that you verify that all of

your constitutive analyses run independently before you systematically build up your one- and two-

way coupled analyses.

The independent analyses executed prior to coupled analysis should attempt to replicate the effects of

the coupled problem as closely as possible. For fluid-structure interaction problems, for example, the

fluid-only analysis could include user-specified motion that approximately models the expected motion

(or range thereof ) from the structural analysis. Similarly, the structure-only analysis could include a user-

specified load that approximately models the expected load (magnitude and distribution) from the

fluid analysis.

Prior to executing two-way coupled analyses, it is also strongly recommended that you execute a set

of one-way coupled analyses. The benefits of building up coupled analyses this way include:

• Augmenting the fully decoupled analyses proposed above with a more accurate approximation of

the inputs expected from the independent analysis

• Verifying the need for a two-way coupled analysis by assessing the sensitivity of the dependent

analysis to inputs expected from the independent analysis

For fluid-structure interaction problems, for example, loads exported from the fluid-only analysis could

be applied in the structure-only analysis. If, under these conditions, a significant deformation due to

the applied loads is observed, then a two-way coupled analysis may be appropriate. Note, however,

that two-way coupled analyses are significantly more computationally expensive (by approximately an

order of magnitude) than one-way coupled analyses.

Execution of a two-way coupled analysis follows once fully decoupled and one-way coupled analyses

are verified to run as expected and the need to execute a two-way coupled analysis is confirmed. Even

at this point, however, difficulties may be encountered during the execution of the two-way coupled

analysis due to the increased complexity of this problem. The following information will aid in debugging

such analyses.


Once any solution difficulties associated with executing fully decoupled and one-way coupled analyses

have been addressed, a two-way coupled analysis may be attempted. The information presented in this



section provides a summary of tools and strategies available to facilitate debugging two-way coupled

analyses. These focus on text based and graphical monitor output, and supplemental output for visual-

ization in ANSYS CFD-Post.

For more information, see the following sections:

Using Text-Based Monitor Output to Debug Coupled Analyses

Using Graphical Monitor Output to Debug Coupled Analyses

Using Supplemental Output to Debug Coupled Analyses

Supplemental Output for Diagnosing Mapping Problems

Using Text-Based Monitor Output to Debug Coupled Analyses

Text-based monitor output is contained in the System Coupling Log (SCL) file that is created in the run

directory. Sections of the SCL file that are most relevant to the debugging process are identified below.

If problems are encountered, you should carefully review all of these sections.

• Setup Validation: This section facilitates review and verification of the input settings made for the system

coupling service. These inputs are validated by the coupling service, and both warnings and errors generated

during validation are reported here. Any automatic corrections applied to the inputs are listed with valid-

ation warnings.

• Mapping Summary: This section summarizes the extent to which the source and target regions associated

with each data transfer are correctly mapped onto one-another. Under normal conditions, diagnostics

should report a nearly perfect mapping. Less than perfect mappings should be critically considered for

their validity.

• Coupled Solution Convergence History: This section summarizes the convergence of both the coupling

participants and the data transfers that target each of the participants. It is strongly recommended that

sufficient coupling iterations be executed, per step, to ensure that the field equations solved by all

coupling participants and the data transfers defined for the coupled analysis converge fully. Note, however,

that the coupling service will advance to the next coupling step, regardless of convergence, once the

maximum number of coupling iterations per step has been executed. You are advised to identify and

understand all reasons for poor convergence of coupling participants or data transfers.

• Error Messages: Fatal errors are reported, as they occur, in the log output. These errors may have originated

either within the coupling service itself or within any of the coupling participants. When such an error

occurs, output from the service and all participants should be critically reviewed.

• Shutdown Reporting: Under normal conditions, the end of the log output generated by the coupling

service reports whether or not the coupled analysis completed successfully. When the analysis does not

complete successfully, additional information is provided as to what may have caused the problem.

For more information on the content of the SCL file see System Coupling Service Log File (scLog.scl_,scLog_##.scl ) (p. 57). Note, as well, that supplemental debug output can also be written to the SCL

file to facilitate debugging. This output is generated by adding debug output specifications to the system

coupling setup.

Similar output files often exist (either by default or by user request) for the coupling participants. For

example, the ANSYS Fluent solver can generate a text based transcript file and the ANSYS Mechanical

APDL solver can generate a text based output file. Please refer to Supported System Couplings (p. 3)

for more information regarding the text based monitor output that they can generate.



Using Graphical Monitor Output to Debug Coupled Analyses

Graphical monitor output is provided in the form of convergence charts within the System Coupling

user interface. This output is most useful to rapidly identify convergence problems. Once such problems

are identified, a review of text monitor output is usually appropriate.

Chartable data includes:

• Data transfer convergence and diagnostics, corresponding to the numerical data written to the system

coupling log file.

• Co-simulation participant convergence, most often corresponding to the (normalized) field equation

convergence values from the solvers.

Each co-simulation participant provides whatever convergence data it can. Thus, different amounts of

data may be available for charting from each co-simulation participant.

Convergence data is collected from a co-simulation participant at the end of that participant’s solution

during a given coupling iteration. In particular, the set of solver substep and solver iteration convergence

data corresponding to the coupling iteration are updated all at once. Thus, if rapid divergence and

failure of a solver occurs during a given coupling iteration, this information will not be included in the

charted output for that iteration.

Using Supplemental Output to Debug Coupled Analyses

At your request, the system coupling service will generate output that supplements the text-based and

graphical monitor output. As discussed below, the supplemental output facilitates the diagnosis of

mapping problems.

Note that visualization of multi-dimensional features (for example, mesh interface regions) of a problem

currently requires the use of an external viewer such as the Results component system (that is, CFD-

Post) in the ANSYS Workbench environment.

Supplemental Output for Diagnosing Mapping Problems

Supplemental output, which is specifically aimed at diagnosing mapping problems, includes:

• Data transfer source and target interface meshes.

• A scalar field indicating (un)mapped nodes.

To enable this output, create and set the expert setting DumpInterfaceMeshes to the value CFDPost .

When this setting is made, one user surface definition file (in a comma separated value, CSV, format)

will be generated by the coupling service during the mapping process for each source and target for

each data transfer. This data is used in the CFD-Post application either using the "Import Surface or Line

Data" functionality or by creating a user surface location directly from the definition file(s).

Once the user surfaces associated with the source and target interface meshes are created in CFD-Post,

they may be visually examined for consistency (for example, if the source and target surfaces or nodes

are coincident). The surface may be colored by the ‘Unmapped’ variable, which will report values of 0

and 1 for unmapped and mapped nodes, respectively. This corresponds to blue and red, respectively,

using the default color map.




Unmapped nodes may also be visualized by inserting a point location with the Method set to Variable

Minimum for the ‘Unmapped’ variable on the surface of interest. Attributes of the plotted points, such

as the symbol shape and size, may be edited to facilitate visualization.


There are several ways to improve the stability of a coupled analysis:

Data Transfer Ramping

Participant Solution Stabilization

Co-Simulation Participants Sequencing

Data Transfer Ramping

In some cases, applying the full magnitude of data on the target side of data transfer interface will ini-

tiate oscillatory convergence or even divergence within and between the coupled co-simulation parti-

cipants. For this reason, the target side data may be ramped from the final value observed in the previous

coupling step (or zero during the first coupling step) to the full magnitude during the initial coupling

iterations within the current step.

For more information about ramping behavior and controls, see Data Transfers (p. 14). For more inform-

ation about the algorithm used for System Coupling’s ramping, see Ramping Algorithm (p. 53).

Participant Solution Stabilization

Solution instabilities that manifest as a very rapid divergence of the coupled analysis may arise if a

given coupling participant is particularly sensitive to data obtained from another participant. In these

cases, it may be advantageous to use various solution stabilization algorithms that have been imple-

mented in the target participant.

For an example of participant solution stabilization, refer to the dynamic mesh system coupling solution

options used in ANSYS Fluent, described in System Coupling Motion in the Fluent User's Guide.

Co-Simulation Participants Sequencing

In general, the driver of the physical problem should be processed first (that is, given a lower sequence

index). If, in a fluid-structure interaction (FSI) simulation, the fluid flow (such as air flow around a wing)

causes the structure (that is, the wing) to deform, then the fluid analysis should be first in the processing

sequence.

The System Coupling infrastructure allows the co-simulation of multiple coupling participants. In many

cases, the execution (for example, solve) sequence of the co-simulation participants is inconsequential.

In some cases, however, the sequence may affect solution stability and/or the time required to execute

the complete coupled analysis.

Note

To improve solution stability, sequential solutions are used by default. To facilitate syn-

chronization of interface geometry, participants that consume geometrical or mesh de-

formations (e.g., the Fluids solver in a Fluid Structure Interaction analysis) are executed

last.



Controlling Participant Sequencing

Participant sequencing controls the order in which co-simulation participants collect data (as prescribed

by defined data transfers) and execute their part of the coupled analysis. Ordering is specifically controlled

by assigning a sequence index to each of the co-simulation participants. Participants with the smallest

sequence index are processed first. If two (or more) participants are assigned the same sequence index,

they are processed simultaneously (that is, required data is first collected from other participants, and

then the participants all execute (for example, solve) simultaneously.

Care is taken to ensure that the geometry and mesh are properly synchronized at the end of each

coupling step for all co-simulation participants. This is required to ensure consistency during post-pro-

cessing and during restarts. An extra ‘partial’ coupling iteration reprocesses all participants that are

targets of deformation or motion-related data transfers. An extra partial iteration is executed once after

all convergence targets are met or the maximum number of coupling iterations for the step is realized.

A warning that extra partial iterations will be performed is provided in the validation output that follows

the setup summary in the System Coupling Service Log File (scLog.scl_, scLog_##.scl ) (p. 57).

When an extra 'partial' coupling iteration is used to properly synchronize the interface geometry and

mesh, there will be no noticeable change in the geometry and mesh during the first coupling iteration

of the subsequent step. This will be clearly evident in convergence chart monitor output as near-zero

values for the change in motion related data transfer values.

Using Sequencing to Reduce Coupled Solution Execution Time

As noted above, all co-simulation participants that share the same sequence index will collect data and

execute their respective parts of the coupled analysis at the same time. This is a way of parallelizing

the coupled solution process and potentially reducing the overall execution time of the coupled analysis.

However, convergence difficulties (for example, more coupling iterations per step) and possible diver-

gence may occur when multiple participants run simultaneously. This is because each participant in the

group that is solved simultaneously collects and uses less up-to-date information from other participants.

The stronger the physical coupling between each participant is, the more likely convergence difficulties

will be encountered if the participants are processed simultaneously.




Tutorial: Oscillating Plate with Two-Way Fluid-Structure Interaction

In this tutorial you will learn how to solve a Fluid-Structure Interaction (FSI) case. You will model struc-

tural deformation in a fluid using System Coupling to coordinate the ANSYS Mechanical and ANSYS

Fluent solvers.

DetailsFeatureComponent

Transient StructuralAnalysis SystemsANSYS Workbench

Fluid Flow (Fluent)

System CouplingComponent Systems

Defining new materialsEngineering Data

ImportGeometryDesignModeler

MeshingMechanical

Defining the physics

Named Selections

Coupled analysis restart

Coupled analysis batch exe-

cution from command line

MeshingMeshing

Defining the physicsANSYS Fluent




Defining the couplingSystem Coupling




VectorPlotsCFD-Post

Animation

This tutorial includes:

Overview of the Problem to Solve

Creating the Project

Optional: Preparing for a Command-line Run

Adding Analysis Systems to the Project

Adding a New Material for the Project

Adding Geometry to the Project

Defining the Physics in the Mechanical Application

Setting up your Fluid Analysis

Defining and Running the Coupling in the System Coupling Application

Viewing Results in CFD-Post



Setting Up and Executing a Coupled Analysis Restart from Workbench

Executing the Coupled Analysis from the Command Line

Note

In the main flow of the tutorial, you use the user interface to completely solve the simulation.

However, at a series of points during the tutorial you have optional instructions that produce

files that will enable you to solve the simulation from the command line. The steps related

to this are:

1. Optional: Preparing for a Command-line Run (p. 82)

2. Preparing for a Command-Line Run of the Structural System (p. 90)

3. Preparing for a Command-Line Run of the Fluent System (p. 96)

4. Preparing for a Command-Line Run of the System Coupling System (p. 100)

5. Executing the Coupled Analysis from the Command Line (p. 105)

If you do not want to solve the simulation from the command line, you may ignore those

steps.


This tutorial uses an example of an oscillating plate within a fluid-filled cavity to demonstrate how to

set up and run a simulation involving a two-way coupled analysis in ANSYS Workbench.

A thin plate is anchored to the bottom of a closed cavity filled with fluid (air), shown in Figure 12: Di-

mensions of the oscillating plate case (p. 80). There is no friction between the plate and the side of the

cavity. An initial pressure of 100 Pa is applied to one side of the thin plate for 0.5 s to distort it. Once

this pressure is released, the plate oscillates back and forth to regain its equilibrium, and the surrounding

air damps this oscillation. You will simulate the plate and surrounding air for a few oscillations to be

able to observe the motion of the plate as it is damped.

Figure 12: Dimensions of the oscillating plate case

To simulate this case, you will set up a two-way Fluid-Structure Interaction (FSI) analysis. You will

model the motion of the oscillating plate using the Mechanical application’s Transient Structural

analysis system. You will model the motion of the fluid in the closed cavity using the Fluent application’s



Fluid Flow (Fluent) analysis system. The two analyses are solved at the same time with the System

Coupling system coordinating the solution process as well as the data transfers between the two ana-

lysis systems.

The two-way coupling involves two data transfers:

• Force data from the motion of the air is received by the Transient Structural analysis system as it solves

the structural behavior over time.

• Displacement data from the motion of the plate is received by the Fluid Flow (Fluent) analysis system

as it solves the fluid behavior over time.

The oscillation of the plate is dependent on time, and so you need to choose appropriate time values

for the coupled transient analysis:

• Time duration is the total time observed in the analysis. In this analysis, you will set the time duration to

be 10 s, which is enough time to observe the plate oscillating a few times. With this time duration, you

will not model the full damping back to the plate’s equilibrium. When setting up a transient analysis, make

sure that you choose a time duration that will allow you to observe the behavior of interest in your system.

• Time step is the size of the time increments that you are solving within your transient analysis. In this

analysis, you will set the time step to be 0.1 s, which is fine enough to observe the oscillations to a reas-

onable degree. When setting up a transient analysis, make sure you choose a time step that works for the

physics you are solving. Too large a time step will miss behavior of the system, and too small a time step

will be computationally expensive.


Create the project by setting up Workbench and importing the project files:

1. Start ANSYS Workbench:

• To launch ANSYS Workbench on Windows, click the Start menu, then select All Programs > ANSYS

15.0 > Workbench 15.0.

• To launch ANSYS Workbench on Linux, open a command line interface and enter the path to runwb2 .

For example:

~/ansys_inc/v150/Framework/bin/Linux64/runwb2

The Project Schematic appears with an Unsaved Project. By default, ANSYS Workbench is configured

to show the Getting Started dialog box that describes basic operations in ANSYS Workbench. Click

the [X] icon to close this dialog box.

2. Create a directory where you will store your project (this is your working directory). For example, under

My Documents , create a directory named SystemCouplingOscillatingPlate.

3. Select File > Save or click Save .

4. Select the path to your working directory to store files created during this tutorial.

5. Under File name, type SystemCouplingOscillatingPlate and click Save.




The project files and their associated folder locations appear under the Files view. To make the

Files view visible, select View > Files from the main menu of ANSYS Workbench.

6. This tutorial uses the geometry file, oscillating_plate.agdb , for setting up the project. To access

tutorials and their input files on the ANSYS Customer Portal, go to http://support.ansys.com/training.

Copy the supplied geometry file, oscillating_plate.agdb , to the user_files directory

that is in the SystemCouplingOscillatingPlate_files directory.

By working with a copy of the geometry file in your working directory, you prevent accidental

changes to the original geometry file.

Optional: Preparing for a Command-line Run

This tutorial runs from within Workbench. However, you also have the option of taking files created

from applications running in Workbench and performing a second system coupling run from a command

line. If you want to try this alternative, follow the instructions below to prepare the locations where this

second system coupling run will be performed. As you work through the tutorial in Workbench, you

will be prompted to add source files from the applications running in Workbench to the directories you

create here.

To prepare a directory structure for executing the analysis from a command line:

1. Create a high-level directory named SystemCouplingOscillatingPlate_CmdLine. This directory

should be a sibling to SystemCouplingOscillatingPlate .

2. In the SystemCouplingOscillatingPlate_CmdLine directory, create subdirectories within

which the Mechanical APDL, Fluent, and System Coupling service executables will be run. Name these

subdirectories: Structural_CmdLine , FluidFlow_CmdLine , and Coupling_CmdLine .


You are doing a two-way FSI analysis by coupling two analysis systems: a Transient Structural system

and a Fluid Flow (Fluent) system. You will use the System Coupling system to couple the other two

systems and to coordinate the solution execution.

To add these three systems to your Workbench project:

1. From the Analysis Systems toolbox located on the left side of the ANSYS Workbench window, select

the Transient Structural template. Double-click the template, or drag it onto the Project Schematic

to create a standalone system.

A Transient Structural system is added to the Project Schematic, with its name selected and ready

for renaming.

2. Type in the new name, Structural, to replace the selected text. In this tutorial, “Structural system”

will be used to refer to the Transient Structural system.

If you missed seeing the selected text, right-click the first cell in the system and select Rename

from the context menu. You will then be able to edit the name.

3. Drag a Fluid Flow (Fluent) analysis system on top of the Structural system’s Geometry cell (A3) and

drop it there.



http://support.ansys.com/training

A Fluid Flow (Fluent) system, coupled to the Structural system, is added to the Project Schematic.

This Fluid Flow (Fluent) system is connected to the Structural system through the Geometry cell

(A3 to B2), and so both of these systems will share the same geometry.

4. Change the name of this system to Fluid. In this tutorial, “Fluid system” will be used to refer to the

Fluid Flow (Fluent) system.

5. Expand the Component Systems toolbox, drag a System Coupling system and drop it to the right of

the Fluid Flow (Fluent) system.

6. Drag the Structural system's Setup cell (A5) and drop it on the System Coupling system’s Setup cell

(C2).

7. Drag the Fluid system's Setup cell (B4) and drop it on System Coupling system’s Setup cell (C2). Now

all three systems are connected for a two-way FSI analysis.

8. Save the project.

The Project Schematic should appear as shown in Figure 13: System Coupling of Transient Structural

and Fluid Flow (Fluent) Systems (p. 83).

Figure 13: System Coupling of Transient Structural and Fluid Flow (Fluent) Systems

The Structural and Fluid systems have various cells. The icons on the right side of each cell provides

visual indications of a cell's state at any given time. In your current Project Schematic in Workbench

(shown in Figure 13: System Coupling of Transient Structural and Fluid Flow (Fluent) Systems (p. 83)),

most cells appear with a blue question mark ( ), indicating that cells need to be set up before continuing

the analysis. As these cells are set up, the data transfer occurs from top to bottom. See Understanding

Cell States for a description of various cell states.

Now that your project systems are in place, you can start working through your analysis. Your current

project systems enables you to perform your analysis by:

• adding a new material,

• sharing the geometry,

• setting up the physics in the Structural system,

• setting up the physics in the Fluid system,




• defining and running the coupling in the System Coupling system, and

• viewing the results in CFD-Post.

Adding a New Material for the Project

In the Project Schematic, the Structural system’s Engineering Data cell (A2) appears in an up-to-date

state because default material is already available for the project. You will use material for the oscillating

plate that is not in the default material available, and so you need to update this cell by adding this

new material to the Engineering Data.

The case requires a new material with properties that allow it to oscillate when pressure is applied. You

will create a new material named Plate, define its properties to be suitable for oscillation, and set it as

the default material for the analysis.

1. On the Project Schematic, double-click the Engineering Data cell (A2) in the Structural system.

Engineering Data opens in a new tab in Workbench. The Outline and Properties views are among

the views that appear.

2. In the Outline of Schematic A2: Engineering Data view, click the empty row at the bottom of the

table to add a new material for the project. Type in the name Plate.

When you click away from that cell, Plate is created and appears with a blue question mark, indic-

ating that its properties need to be defined.

3. From the Toolbox on the left, expand Physical Properties. Select Density and drag it onto the cell

containing Plate (A4) in the Outline of Schematic A2: Engineering Data view. If the toolbox is not

visible by default, select View > Toolbox to make it visible.

Density is added as a plate property in the Properties of Outline Row 4: Plate view, as shown in

the following figure.



4. In the Properties of Outline Row 4: Plate view, set the Value of Density (B2) to 2550 kg m^-3. Do

not type in units.

5. In the toolbox under Linear Elastic, drag Isotropic Elasticity onto Plate (A4) in the Outline of

Schematic A2: Engineering Data view.

Isotropic Elasticity is added as the plate property in the Properties of Outline Row 4: Plate view.

6. In the Properties of Outline Row 4: Plate view, expand Isotropic Elasticity by clicking the plus sign.

Now set Young’s Modulus to 2.5e06 [Pa] and Poisson’s Ratio to 0.35. Do not type in units.

The desired plate data is created and is available to the remaining cells in the Structural system.

The next step is to set Plate as the default material for the analysis as outlined below:

1. In the Outline of Schematic A2: Engineering Data view, under Material, right-click Plate (A4) and

select Default Solid Material For Model.

2. From the main menu, select File > Save to save material settings to the project.

3. Close the Engineering Data tab to return to the Project Schematic.


You will add geometry to your project by importing an existing DesignModeler file. Once you add the

geometry, it will be shared between the Structural and Fluid systems because you have connected their

geometry cells in the Project Schematic. All of the geometry parts have to be unsuppressed at this point

in your project so that they are available for use later in the Structural and Fluid systems.

1. On the Project Schematic, right-click the Structural system’s Geometry cell (A3) and select Import

Geometry > Browse.

2. In the Open dialog box, browse to your working directory, select SystemCouplingOscillating-Plate_files > user_files > oscillating_plate.agdb from your working directory, and

click Open.

3. In the Structural system, double-click the Geometry cell (A3) to edit the geometry using DesignModeler.

The DesignModeler application opens in a separate window.

4. In DesignModeler’s Tree Outline on the left, expand the branch 2 Parts, 6 Bodies to see all of the

bodies that compose the geometry. The one solid body is listed, and under Part are the five fluid

bodies. Ensure that all of these bodies are already unsuppressed (they should all have small green check

marks).

5. The geometry is set up for the project. Save any changes by selecting File > Save Project from the

main menu in DesignModeler, and then select File > Close DesignModeler to return to the Project

Schematic.

The updated geometry is now available for both the Structural and Fluid systems.

Later in the tutorial, when you generate the structural mesh, the fluid bodies will first be suppressed.

Similarly, when you generate the fluid mesh, the solid body will be suppressed. You will suppress these




bodies from within the Mechanical and Meshing applications, so no further changes are needed in

DesignModeler.

Note

Because the Structural system’s Geometry cell (A3) shares its content directly with the Fluid

system’s Geometry cell (B2), you can edit the geometry only through the Structural system’s

Geometry cell (A3).


In the Mechanical application, you are setting up the structural analysis and defining the coupling inter-

face. You will not solve the structural analysis from the Mechanical application because you will use

the System Coupling system to solve both structural and fluid systems at the same time.

When setting up your own two-way coupled analysis, it is a best practice to set up and solve the

structural analysis within the Mechanical application before continuing with your coupled analysis. If

issues occur within your structural system, the isolated analysis is easier to troubleshoot than the more

complex coupled analysis.

The structural Geometry cell (A3) is up-to-date, and so you start your setup by generating the structural

mesh. This section describes the step-by-step definition of the structural physics:

Generating the Mesh for the Structural System

Assigning the Material to the Geometry

Setting the Basic Analysis Values

Inserting Loads

Preparing for a Command-Line Run of the Structural System

Completing the Setup for the Structural System

Generating the Mesh for the Structural System

Generate the mesh for the Structural system directly in the Mechanical application:

1. On the Project Schematic, double-click the Structural system’s Model cell (A4) to open the Mechanical

application.

The Mechanical application opens in a separate window.

2. In Mechanical’s Outline on the left, expand Geometry to see the two geometries, solid and Part.

3. For the structural analysis, you need to generate the mesh for only the solid body. To do this, you need

to first suppress the Fluid bodies.

Right-click the Part geometry (which contains all of the fluid bodies), and select Suppress Body.

The fluid bodies are now suppressed and their status changes to an x mark. You now will see only

the solid body in the Graphics view. Click Zoom to Fit to view the entire model in the Graphics

view.

4. You will define the mesh by marking divisions on the edges of the solid. These divisions will be used

as guides for the mesh creation:



a. Click Edge .

b. Click an edge that lies parallel to the X axis.

c. In the Outline, right-click Mesh and select Insert > Sizing.

d. Beside Type, select Number of Divisions from the drop-down menu.

e. Beside Number of Divisions, select 1.

5. Repeat steps a to d to create 10 divisions on an edge that is parallel to the Y axis and 4 divisions on

an edge that is parallel to the Z axis. To summarize:

Number of DivisionsEdge Direction

1X axis

10Y axis

4Z axis

6. In the Outline, right-click Mesh and select Generate Mesh from the shortcut menu.

A hex mesh is generated on your solid body.


When you defined the Plate material, you set it to be the default for your solid body. In the Mechanical

application, you can see that this material is set correctly.

1. In the Mechanical’s Outline on the left, select Project > Model > Geometry > solid.

2. In the Details of “solid”, ensure that Material > Assignment is set to Plate. Otherwise, click the ma-

terial name and use the arrow that appears to make the appropriate change.


You now need to set up information about the transient analysis’ time steps, which are the basic ana-

lysis values needed for the transient structural analysis.

The time step (0.1 s) is chosen to be an appropriate size to observe the plate’s oscillations. The time

duration (10 s) is chosen so that the plate oscillates a few times during the analysis. These time settings

are dependent on the physics that you are observing, including the material properties of the plate.

When setting your own transient analysis, make sure that you choose time settings appropriate to the

physics you are solving.

1. In the Mechanical application’s Outline view, select Project > Model > Transient > Analysis Settings.

The details of Analysis Settings appear in the Details of “Analysis Settings” below the Outline

view.

2. In the Details of “Analysis Settings”, specify the following settings under Step Controls (do not type

units next to the time values):




1. Set Step End Time to 10 .

2. Set Auto Time Stepping to Off .

3. Set Time Step to 0.1 .

Inserting Loads

The loads applied for the structural analysis are equivalent to the boundary conditions in a fluid analysis.

In this section, you will set the following loads and interface:

• a fixed support on the bottom of the plate

• a fluid-solid interface where the plate interacts with the fluid

• a pressure load on one side of the plate, to start the oscillation

On the surfaces of the plate that lie coincident with the symmetry planes, you will not set a load. With

no load set, the default of an unconstrained condition will be applied on these two surfaces. For this

particular case, this unconstrained condition is a reasonable approximation of the frictionless support

that would otherwise be applied.

Defining the Fixed Support

The fixed support is needed to hold the bottom of the thin plate in place. Set up the fixed support:

1. Right-click Transient in the Outline view, and select Insert > Fixed Support from the shortcut menu.

2. Rotate the geometry using the Rotate button so that the bottom (low-y) face of the solid is visible,

then select Face and click the low-y face.

That face is highlighted to indicate the selection.

3. In the Details of “Fixed Support” view, click Apply beside Geometry to set the fixed support.

If the Apply button is not visible, select Fixed Support in the Outline view and, in the Details

view, click the text next to the Geometry setting to make the Apply button reappear.

The text next to the Geometry setting changes to 1 Face .

Defining the Fluid-Solid Interface

The fluid-solid interface defines the interface between the fluid in the Fluid system and the solid in the

Structural system. Data will be exchanged across this interface during the execution of the simulation.

When setting up your structural system for a coupled analysis, you need to define this interface on regions

in the structural model that will receive force data from the Fluid system.

1. In the Outline view, right-click Transient and select Insert > Fluid Solid Interface from the shortcut

menu.



2. Using the same face-selection procedure described earlier in Defining the Fixed Support (p. 88), select

the three faces of the geometry that form the interface between the structural model and the fluid

model (low-x, high-y and high-x faces). Hold down Ctrl to be able to select multiple faces.

3. In the Details of “Fluid Solid Interface”, beside Geometry, click Apply.

The text next to the Geometry setting changes to 3 Faces .

Note that this load (fluid-solid interface) is automatically given an Interface Number of 1.

Defining the Pressure Load

The pressure load on one side of the plate provides the initial pressure of 100 Pa for the first 0.5 s of

the simulation. This pressure to the plate starts the oscillation. It is defined using tabular data.

1. In the Outline view, right-click Transient in the tree view and select Insert > Pressure from the

shortcut menu.

2. In the Viewer, select the low-x face. In the Details of “Pressure” view beside Geometry, click Apply.

The text next to the Geometry setting changes to 1 Face .

3. In the Details of “Pressure” view, click the cell next to Magnitude, and using the arrow that appears,

select Tabular.

The Tabular Data view appears on the bottom right of the Mechanical application window. The

times of 0 s and 10 s are the beginning and end of your analysis, based on the time duration (10

s) that you specified earlier.

4. In Tabular Data, set a pressure of 100 Pa in the table row corresponding to a time of 0. Do not type

in units.

5. You now need to add two new rows to the table. Do this by typing the new time and pressure data

into the empty row at the bottom of the table. Notice that the rows are automatically re-ordered based

on the time value. Add the data from Table 4: Tabular Data for Step Pressure Load (p. 89).

Table 4: Tabular Data for Step Pressure Load

Pressure (Pa)Time (s)

1000

1000.5

00.51

010

You now have tabular data similar to a step function for your pressure, with 100 Pa applied for 0.5

s. The step function is displayed in the graph to the left of the table.

6. The settings for the structural physics are now complete. Save these settings by selecting File > Save

Project from Mechanical’s main menu.

7. If you do not intend to execute a command line run using the set up from the Mechanical system,

proceed to Completing the Setup for the Structural System (p. 90). If you do intend to execute a com-

mand line run, continue with the next section.




Preparing for a Command-Line Run of the Structural System

If you intend to execute a command-line run using the set up from the structural system:

1. From the Mechanical application, select Tools > Write Input File.

2. Specify the path and APDL Input File (SystemCouplingOscillatingPlate_CmdLine\struc-tural.dat ) that you will use later.

Tip

The Write Input File option is available only if you have Transient (A5) selected in the

Outline tree.

Note

Though out of the scope of this tutorial, below is information about augmenting your

structural setup, and transferring the structural setup from the Mechanical application to the

Mechanical APDL application.

• In some cases, you may need to augment your structural setup in the Mechanical APDL applic-

ation. If this is the case, then open that application and select File > Read Input From to

choose the .dat file created by Mechanical. Once the .dat file has been read, make your

setup modifications and write a Mechanical APDL Database file using File>Save As Jobname.db

or File >Save As. Starting the Mechanical APDL solver from the created database file is explained

later in the tutorial.

• Transferring the structural setup from the Mechanical application to the Mechanical APDL ap-

plication is facilitated in ANSYS Workbench. To do this, right-click the Mechanical system's

Setup cell (A5), and select Transfer to New > Mechanical APDL. Once the new Mechanical

APDL system is introduced, update the upstream Mechanical system's Setup cell (A5). The

setup will be read into the Mechanical APDL user interface by right-clicking that system's

Analysis cell and selecting Edit in Mechanical APDL.

Completing the Setup for the Structural System

On the Project Schematic, the Structural system’s Setup cell (A5) appears in an update-required state.

To complete the setup in the Structural system, you need to ensure that all the data is in the right state

in the Project Schematic.

1. In the Structural system, right-click the Setup cell (A5) and select Update from the shortcut menu.

The status of the Setup cell changes to up-to-date. All cells in the Structural system down to the

Setup cell should now appear in an up-to-date state.

2. From the main menu, select File > Save to save the project.

The set up for the Structural system is complete. Remember that you will not solve the structural ana-

lysis from the Mechanical application because you are using the System Coupling system to solve both

Structural and Fluid systems at the same time. In the next section, you will set up the Fluid system.




You will use the Fluent application to set up your Fluid system, but first you need to generate the mesh

using the Meshing application. The fluid Geometry cell (B2) is up-to-date because it shares the geometry

with the structural analysis, and so you start your Fluid system’s setup with creating a mesh.

Generating the Mesh for the Fluid System

You will generate a mesh for the Fluid system using the Meshing application. For this geometry, you

will use a swept mesh across the x-y plane, creating a hex mesh with a depth of one element.

1. In the Project Schematic, double-click the Fluid system’s Mesh cell (B3) to open the Meshing application.

The Meshing application appears in a separate window.

2. In the Meshing application’s Outline view on the left, expand Geometry to see the two geometries,

solid and Part.

3. For the fluid analysis, you need to generate the mesh for only the fluid bodies. To do this, you need to

first suppress the structural body.

Right-click solid and select Suppress Body

The solid body is now suppressed and its status changes to an x mark. You now will only see the

fluid bodies in the Graphics view.

4. In the Outline on the left, click Mesh. In the Details of “Mesh” below, under Defaults, notice that the

Physics Preference is set to CFD and Solver Preference is set to Fluent.

5. Now you need to define sweep as the meshing method, and set up all of the information that the

sweep method needs:

a. In the Outline, right-click Mesh and select Insert > Method.

Automatic Method will appear under Mesh

b. Click Body , and then select all five fluid bodies in the Graphics view. Use the Ctrl key to select

multiple bodies. Note that the fifth fluid body is very thin, and is above the plate.

c. With all five bodies selected, in the Details of “Automatic Method” – Method, beside Geometry

click No Selection. Click the Apply button that appears.

The text next to Geometry changes to 5 Bodies .

d. Under Definition, set Method to Sweep.

Notice that in the Outline above, under Mesh, the method is now renamed to Sweep Method.

e. In the Details of “Sweep Method” – Method, next to Src/Trg Selection, click Automatic. Using

the arrow that appears, select Manual Source.

Manual Source enables you to dictate which surfaces are used as the source for the sweep

meshing. Source is highlighted, indicating that information about which surfaces to use is

needed.




f. Select Face , then Ctrl-select all five fluid faces on one of the walls in the x-y-plane (either side

of the wall will work).

g. In the Details view, beside Source, click No Selection. Click the Apply button that appears.

The text next to Source changes to 5 Faces .

h. Set Free Face Mesh Type to All Quad so that all of the mesh elements are quadrilateral.

i. Next to Sweep Num Divs, set the value to 1.

j. In the Outline above, click Mesh. In the Details of “Mesh”, expand Sizing and set Min Size to

0.06 and Max Face Size to 0.2 . These settings control the size of the mesh elements that will

be generated.



6. Now that all of the settings for your swept mesh are complete, you need to generate the mesh. In the

Outline, right-click Mesh and select Update.

The swept mesh that you have defined is now generated for your fluid bodies.

7. Select File > Save Project, and then File > Close Meshing to close the Meshing application.

Defining the Physics in the ANSYS Fluent Application

In the Fluent application, you are setting up the fluid analysis, and defining the coupling interface. You

will not solve the fluid analysis from the Fluent application because you are using the System Coupling

system to solve both structural and fluid systems at the same time.

When setting up your own two-way coupled analysis, it is a best practice to set up and solve the fluid

analysis before continuing with your coupled analysis. If issues occur within your fluid system, the isolated

analysis is easier to troubleshoot than the more complex coupled analysis.

This section describes the step-by-step definition of the fluid physics:

Adding the Solution Setup Settings

Defining the Dynamic Mesh

Adding the Solution Settings

Preparing for a Command-Line Run of the Fluent System

Adding the Solution Setup Settings

You now need to open your analysis in the Fluent application, set the Fluid analysis to be transient,

and add material to the fluid geometry.

1. In the Project Schematic, double-click the Fluid system’s Setup cell (B4) to open the Fluent application.

2. The Fluent Launcher opens in a new window. Under Options, select Double Precision.

3. Use the remaining default options (3D and serial), and click OK to close the Fluent Launcher.

The Fluent application opens in a new window, and the mesh file is automatically loaded.

4. On the left, select Solution Setup > General. Under Time, click the Transient option.

5. On the left, select Solution Setup > Materials > Air to assign material to your geometry. Click the

Create/Edit button, and in the dialog box that appears, for Density (kg/m3) type 1 and Viscosity

(kg/m-s) type 0.2 . Do not type units.

Click Change/Create to save these changes, and then click Close.

6. Under Solution Setup > Models, note that by default, the viscous model is laminar and the energy

model is turned off. No changes are needed to these settings.

Defining the Dynamic Mesh

A dynamic mesh is needed for any coupled analysis where a system receives displacements. In this tu-

torial, the plate is oscillating back and forth, and the dynamic meshing settings determine how the

mesh of the fluid bodies react to this deformation of the moving structural body.

The mesh on the fluid-structural interface is static, so as the fluid mesh is modified to accommodate

the deformation in the transient system, the mapping on this coupling interface stays consistent.




Set up the dynamic mesh:

1. On the left, select Solution Setup > Dynamic Mesh.

2. Check the Dynamic Mesh option in the panel. The settings for Dynamic Mesh are now available.

3. Under Mesh Methods, Smoothing is checked by default. Click the Settings button to specify the settings

for the smoothing used.

The Mesh Method Settings dialog box appears.

a. On the Smoothing tab, set Method to Diffusion.

b. For the Diffusion Parameter, type 2. Click OK to close the Mesh Method Settings dialog box.

4. Under Dynamic Mesh Zones, click Create/Edit to specify which zones in your geometry will have dy-

namic meshing.

The Dynamic Mesh Zones dialog box appears.

5. Define the dynamic mesh settings needed for the surface “symmetry1”, which is the wall in the x-y

plane that goes through the origin. This surface will be affected by the solid body’s displacement, and

its mesh needs to be able to deform.

a. In the Dynamic Mesh Zones dialog box, under the Zone Names drop down list, select the zone

“symmetry1”.

b. Set its Type as Deforming.

c. Select the Geometry Definition tab.

d. Specify the Definition as “plane”.

e. Specify Point on Plane as 0,0,0

f. Specify Plane Normal as 0,0,1

g. Click Create at bottom of dialog box to create this dynamic mesh zone.

The list of Dynamic Mesh Zones on the right side of the dialog box now includes the “sym-

metry1”.

6. Define the dynamic mesh settings needed for the surface “symmetry2”, which is the second wall in the

x-y plane. This surface will be affected by the solid body’s displacement, and its mesh needs to be able

to deform.

a. Under the Zone Names drop down list, select the zone “symmetry2”.

b. Set its Type as Deforming.

c. Select the Geometry Definition tab.

d. Specify the Definition as “plane”.

e. Specify Point on Plane as 0,0,0.4



f. Specify Plane Normal as 0,0,1

g. Click Create at bottom of dialog box to create this dynamic mesh zone.

The list of Dynamic Mesh Zones now includes the “symmetry2”.

7. Define the dynamic mesh settings needed for the surface “wall_bottom”, which is the two surfaces on

the bottom of the fluid zones (the two surfaces are interrupted by the solid body in the middle of the

geometry). This surface is not affected by the solid body’s displacement, and so its mesh should remain

stationary.

a. Under the Zone Names drop down list, select the zone “wall_bottom”.

b. Set its Type as Stationary, then click Create at bottom of dialog box to create this dynamic mesh

zone.

The list of Dynamic Mesh Zones now includes the “wall_bottom”.

8. Repeat the previous step's instructions to create stationary dynamic mesh zones for the three surfaces

below. These three surface complete the enclosed cavity, and they are not affected by the solid body’s

displacement. Their mesh should remain stationary.

• “wall_top”

• “wall_inlet”

• “wall_outlet”

9. Define the dynamic mesh settings needed for the surfaces in the zone “wall_deforming”, which are the

surfaces surrounding the solid body. These surface will deform throughout the simulation.

a. Under the Zone Names drop down list, select the zone “wall_deforming”.

b. Set its Type as System Coupling, then click Create at bottom of dialog box to create this dynamic

mesh zone.

The list of Dynamic Mesh Zones now includes the “wall_deforming”.

10. You now have seven dynamic mesh zones defined and listed on the right of the dialog box. Click Close.

Adding the Solution Settings

Set the solutions settings in the Fluent application so that your fluid system is ready to be solved:

1. On the left side of the Fluent application, select Solution > Solution Methods.

a. Under Pressure-Velocity Coupling > Scheme, select Coupled.

b. Under Spatial Discretization > Momentum, select Second Order Upwind.




2. On the left side of the Fluent application, select Solution > Calculation Activities, then specify Autosave

Every (Time Steps) to be 2.

3. On the left side of the Fluent application, select Solution > Run Calculation, then:

a. Specify Number of Time Steps to be 10 . Note that the system coupling’s number of time steps

will override this value.

b. Specify the Max Iterations/Time Step to be 5. This value is the maximum amount of times that

Fluent can iterate within a coupling iteration.

c. Leave the default Time Step Size (s) as 1, but note that the system coupling’s time step size will

override this value.

4. On the left side of the Fluent application, select Solution > Solution Initialization. Under Initialization

Methods, click the Standard Initialization option.

5. In Solution > Solution Initialization, click Initialize.


7. If you intend to execute a command line run using the setup from the Fluent system, go to Preparing

for a Command-Line Run of the Fluent System (p. 96).

8. If you do not intend to execute a command line run using the setup from the Fluent system, Select

File > Close Fluent to close Fluent and to return to the Project Schematic.

The setup for the Fluid system is complete. Remember that you will not solve the fluid analysis

from the Fluent application because you are using the System Coupling system to solve both

structural and fluid systems at the same time. In the next section, you will set up the System

Coupling system.

Proceed to the section Defining and Running the Coupling in the System Coupling Applica-

tion (p. 97).

Preparing for a Command-Line Run of the Fluent System

If you intend to execute a command line run using the set up from the Fluent system, select File >

Export > Case from the main menu in the Fluent user interface, and specify the path and Case File

(SystemCouplingOscillatingPlate_CmdLine\fluidFlow.cas ) that you will use later.

Important

You should perform this step before updating the coupled solution within the Workbench

environment for the following reasons:

• Editing the Fluent system’s Setup cell after a solution is executed will clear all existing solution

files.

• Editing the Fluent system’s Solution cell after a solution is executed will load the most recent

(rather than the original) case and data files.



You may now close Fluent.


In the System Coupling system, you are setting up the coupling between your Structural and Fluid

analyses. You will use the System Coupling system to solve both of these analyses at the same time.

Notice that in the Structural and Fluid systems, all of the cells up to Setup are marked as up-to-date.


To set up the transient analysis settings for your coupled analysis:

1. In the Project Schematic, double-click the System Coupling system’s Setup cell (C2).

In the dialog box, click Yes to allow upstream data to be read. The System Coupling system is ob-

taining data from the Structural and Fluid systems’ Setup cells (A5 and B4).

The System Coupling application opens in a new tab in your Workbench project.

2. In Outline of Schematic C1: System Coupling, select System Coupling > Setup > Analysis Settings.

3. In Properties of Analysis Settings (on the bottom left):

a. Set Duration Controls > End Time to 10 .

The end time is the same as the Structural system’s time duration. The choice of 10 s gives

enough time to observe the plate oscillating a few times. System Coupling’s end time value

always overrides the number of time steps specified in the Fluent application.

b. Set Step Controls > Step Size to 0.1 .

The coupling iteration size is same as the transient analysis’ time step, and the choice of 0.1

s is small enough for use to observe the plate’s oscillations to a reasonable degree. System

Coupling’s step size value always overrides the time steps size specified in the Fluent applica-

tion.

c. Set Maximum Iterations to 20 .

A large buffer is given by setting the maximum iterations to 20. It is unlikely that the system

will need many coupling iterations within each coupling step, but this limit will allow the

solution to continue if there is trouble converging within a coupling step.

Creating the Data Transfers

For your two-way coupled analysis, data from the Structural and Fluid solutions need to be shared

throughout the solution process. System Coupling coordinates the transfer of data between these two

systems using the Data Transfers that you create.

1. In Outline of Schematic C1: System Coupling, expand System Coupling > Setup > Participants until

all region components are visible.




2. Ctrl-select the "wall_deforming" (from the Fluid system) and "Fluid Solid Interface" regions (from the

Structural system). With both selected, right-click on one of those regions and select Create Data

Transfer.

Under System Coupling > Setup > Data Transfers, Data Transfer and Data Transfer 2 are created:

a. Data Transfer: here, the surface of the Fluid system around the plate transfers force to the surface

of the Structural system around the plate.

b. Data Transfer 2: here, the surface of the Structural system around the plate transfers displacement

to the surface of the Fluid system around the plate.

Click on System Coupling > Setup>Data Transfers > Data Transfer. In the Properties of Data-

Transfer on the bottom left, notice that the source, target and variable transferred are already

defined for each of these data transfers. These settings are also already defined for Data Transfer

2.

Preparing System Coupling for Restarts

You should ensure that System Coupling is producing restart data, in the event that the System Coupling

analysis needs to be restarted.

1. Under System Coupling > Setup > Execution Control, select Intermediate Restart Data Output. The

restart output frequency for the system coupling analysis is defined and controlled by these settings.

2. In Properties of Intermediate Restart Data Output:

• Set Output Frequency to At Step Interval.

• Set Step Interval to 5.

3. Select File > Save to save your settings before solving.

Note

Recall that earlier, the Fluent auto-save frequency was set to 2 so that Fluent will output

result files (case and data files) every two time steps (that is, 2, 4, 6, 8, 10, etc.). Fluent

will also output additional result files at 5, 10, 15, 20 etc. based on the Step Interval

frequency specified for the Intermediate Restart Data Output. In CFD-Post, both sets

of files will be available for post-processing.

Solving and Restarting the Coupled Analysis

During the solution process, the System Coupling system coordinates the solving of your Structural and

Fluid systems as well as the data transfers between these two systems. The Fluid system solves using

the Structural solution’s displacement data, and the Structural system solves using the Fluid solution’s

force data.

1. To start solving the coupled analysis, in Outline of Schematic C1: System Coupling, right-click Solution

and select Update.

The solution progress begins, and progress is summarized in the Scene Chart Monitor and Solution

Information views, as well as the Workbench schematic progress view. This solution will run for



100 coupling steps because you specified an end time of 10 s in System Coupling (“time duration”

in Mechanical), and each coupling step represents 0.1 s (“step size” in System Coupling, and “time

step” in Mechanical).

Note that you can alternatively start solving the coupled analysis from Workbench’s Project

Schematic:

a. To return to the Project Schematic, click on the Project tab in Workbench. To start the solution

process from the Project Schematic view, right-click the System Coupling system’s Solution cell

(C3) and choose Update.

Notice that the Structural and Fluid systems’ Solution cells’ (A6 and B5) update operations

are disabled because the coupled solution process must be run through the System Coupling

system.

b. Click on the System Coupling tab to return to the System Coupling system and observe the coupled

solution progress.

If you closed the System Coupling application and so there is no System Coupling tab, you

can re-open the System Coupling user interface by double-clicking on its Solution cell (C3).

2. On the bottom right of the screen, click on Show Progress to see the progress of your solution.

3. As your analysis is solved, in the Solution Information view, information from the System Coupling

Log file is displayed. Useful information includes:

a. Each coupling step and coupling iteration is recorded with information about convergence of the

data transfer.

b. At the beginning of the file (scroll up in your Solution Information view), there is an overview of

the participants (the Fluid and Structural system), the data transfers, the System Coupling settings,

and a mapping summary.

c. The Mapping Summary has information about the percentage of nodes on your fluid-structure in-

terface that are mapped. This information is used to determine the quality of the mapping in your

system.

4. Restart data will be output during the solution process. An additional note will be seen in the System

Coupling log output under Solution Information indicating the name and frequency of the system

coupling result file. For example, the intermediate result file is written: scResult_01_000005.scr. The restart

data for Fluent will also be output at the same frequency during the coupled solution. When the coupled

solution completes, Mechanical restart files (that is, file.r001, file.r002 etc.) will be visible in the Workbench

project files (that is, they are automatically transferred from the solver temporary/scratch folder). The

file naming convention is such that file.r001 refers to a Mechanical restart file at step 5, file.r002 refers

to a Mechanical restart file at step 10, and so on.

5. The System Coupling solution is complete when the System Information view reads “System coupling

run completed successfully.”

6. Select File > Save to save the project, and then click on the Project tab to return to the Project

Schematic.




Preparing for a Command-Line Run of the System Coupling System

If you intend to execute a command-line run using the setup from the System Coupling system, you

need to export the System Coupling Input (SCI) file. To do this:

1. In your Project Schematic, make sure that the System Coupling Setup cell (C2) is in an up-to-date state.

2. If your System Coupling tab is not open, double-click System Coupling’s Setup cell (C2).

3. From the System Coupling tab, in the main menu, select File > Export SCI File.

4. Specify the path and SCI file (SystemCouplingOscillatingPlate_CmdLine\coupling.sci )

that you will use later.

5. Select File > Save to save the project, and then click on the Project tab to return to the Project

Schematic.


You will use CFD-Post to view the results of your coupled analysis. You have simulated the plate oscil-

lating in a closed cavity filled with air. The results you have obtained show the plate and surrounding

air for a few oscillations, and you will be able to use CFD-Post to see the motion of the plate as it is

damped.

In Workbench, you need to set up the Project Schematic so that CFD-Post can read the solution of

your Structural and Fluid systems.

To view the results in CFD-Post:

1. In the Project Schematic, drag the Structural Solution cell (A6) to the Fluid Results cell (B6).

2. Double-click the Fluent Results cell (B6) in the Fluid system to launch CFD-Post.

CFD-Post opens in a new window. Both sets of results are loaded into the CFD-Post session, and

are ready for you to view.

Creating an Animation

An animation is a good way to view results in a transient analysis. In this animation, you will show:

• The pressure and velocity of the fluid on the symmetry plane

• The deformation of the plate geometry, with stress visible

Set up your animation:

1. From the task bar at the top of the CFD-Post application, select Tools > Timestep Selector to open

the Timestep Selector dialog box.

The Timestep Selector dialog box shows the results time history for both Fluent and MAPDL system

coupling.

2. In the Timestep Selector dialog box, on the Fluid tab, select a Time of 0.2 s for the Fluid case, then

click Apply.



Close the Timestep Selector dialog box.

3. Under Cases > Fluid at 0.2s > Part Fluid, check the “symmetry1” zone under the Fluid case to display

that zone, then double-click to edit it.

a. In Details of symmetry1, on the Color tab set the Mode to Variable and set Variable to Pressure.

b. On the Render tab, clear the Lighting check box and check Show Mesh Lines.

c. Click Apply to save your changes. The pressure at 0.2 s is now visible on the one side of the fluid

geometry.

4. Under Cases > Structural at 0.2s > Default Domain, check the Default Boundary zone, then double-

click to edit it.

a. In the Details of Default Boundary, on the Color tab, set the Mode to Variable and set Variable

to Von Mises Stress.

b. On the Render tab enable Show Mesh Lines.

c. Click Apply. Stress is now visible on the structural body.

5. From the task bar at the top of the CFD-Post application, select Insert > Vector to create a vector plot.

Accept the default name and click OK.

a. In the Details view on the Geometry tab, set the Locations to symmetry1, set Sampling to Face

Center, and ensure that Variable is set to Velocity.

b. On the Symbol tab, set Symbol to Arrowhead3D.

c. Click Apply. A vector plot of the velocity is now visible on the one side of the fluid geometry.

6. In the Outline under User Locations and Plots, clear the Default Legend View 1 check box.

7. From the task bar at the top of the CFD-Post application, select Insert > Text and click OK to accept

the default name.

a. In the Details of Text 1 view, for Text String, type Time = . Check the Embed Auto Annotation,

and from the Expression drop-down list select Time Value.

b. On the Location tab, set X Justification and Y Justification to None, and set the Position text

as 0.1 in the first field, and 0.2 in the second field.

c. Click Apply.

The corresponding transient results are loaded into the Animation in CFD-Post, and when you run the

animation, you can see the mesh move in both the Fluent and Mechanical regions.

1. Zoom in so that you can see the oscillating plate clearly.

2. At the top of the CFD-Post application, click Animation .




The Animation dialog box appears.

3. Select Keyframe Animation.

4. In the Animation dialog box:

a. Click New to create KeyframeNo1 .

b. Highlight KeyframeNo1 , then change # of Frames to 48 .

c. Load the last timestep (100 ) using the Timestep Selector (found at the top of the CFD-Post In-

terface).

d. Back in the Animation dialog box, click New to create KeyframeNo2 .

The # of Frames parameter has no effect for the last keyframe, so leave it at the default value.

e. Click the More Animation Options button , then check the Save Movie check box.

f. Click Browse next to Save Movie to set a path and file name for the movie file.

If the file path is not given, the file will be saved in the directory from which CFD-Post was

launched.

g. Click Save.

The movie file name (including path) will be set, but the movie will not be created yet.

h. If frame 1 is not loaded (shown in the F: text box in the middle of the Animation dialog box), click

To Beginning to load it.

Wait for CFD-Post to finish loading the objects for this frame before proceeding.

i. Click Play the animation .

The movie will be created as the animation proceeds. This process will be slow, since a timestep

must be loaded and objects must be created for each frame.

j. Save the results by selecting File > Save Project from the main menu.

k. Close the animation dialog box. Your animation is now saved in the file path you specified. You

can play the video in any media player.

Plotting Results on the Solid

You will use a chart to display the deformation of the solid body. One point at the top of the plate is

used to track the displacement in the chart. This chart is a useful way to view the damping that occurs

in the plate’s motion due to the interaction with the fluid.

1. Create a point in the solid domain by using node number 77. This point is at the top corner of the

solid body, and will be used to track the deformation of the plate.



a. From the task bar at the top of the CFD-Post application, select Insert > Location > Point. Click

OK to accept the default name.

b. In the Details view, on the Geometry tab, set Domains to Default Domain, set Method to Node

Number, and set Node Number to 77.

c. Click Apply. On your model, cross hairs appear on node number 77, so you can see where this

point is on your solid body.

2. To view the deformation using the point you just created, insert an XY Transient Chart for the data at

this node (“Point 1”). In the chart you create, the x-axis is time, and the y-axis is the total mesh displace-

ment.

a. From the task bar at the top of the CFD-Post application, select Insert > Chart; click OK to accept

the default name.

b. In the Details view, on the General tab, set Type to XY - Transient or Sequence

c. On the Data Series tab, for Name type System Coupling, and set Location to Point 1.

d. On the X Axis tab, ensure that the Expression is Time.

e. On the Y Axis tab, set the Variable to Total Mesh Displacement X.

3. Click Apply to generate the chart of mesh displacement over time.

After the chart is generated, note the damping that is visible in the plate’s motion. The plate does

not return to equilibrium in this chart because of the length of time we chose for the simulation

of this case. To see the full damping of the system, you would need to simulate the case for a

longer time duration.

4. Save the project and then select File > Close CFD-Post.

Post-Processing in Mechanical

You can also see the structural results of your FSI analysis in the Mechanical application. Note that the

Mechanical system does not have any information about results on the fluid bodies.

1. From the Project Schematic, double-click the Results cell (A7) to relaunch ANSYS Mechanical.

The Mechanical application opens in a new window.

2. In the Outline view, right-click Solution A6 and select Insert > Stress > Equivalent (von Mises) results.

3. Right-click Solution A6 again and select Insert > Deformation > Directional results.

4. Right-click Solution A6 again and select Evaluate All Results.

The equivalent stress and directional deformation of the place are now visible on your model.

5. Under Solution A6 click Equivalent Stress to view the stress on the structural body.

6. Under Solution A6 click Directional Deformation to view the deformation of the structural body.




7. From your Project Schematic, save the project.

All systems are now complete and the Project Schematic is up-to-date.

Setting Up and Executing a Coupled Analysis Restart from Workbench

1. In the Mechanical application,

a. Under Project > Model > Transient, select Analysis Settings.

b. In Analysis Settings Details, set Restart Type to Manual.

c. In Analysis Settings Details, set Current Restart Point to Load Step 50, Substep 1 (that is, 5s).

d. Close ANSYS Mechanical.

2. From the Project Schematic, double-click the Fluid Solution cell (B5):

a. From the File menu, select Solution Files....

b. In the Solutions Files dialog box that appears, click on 100 time steps, 10s - Current to deselect

it, and then click on 50 time steps, 5s to select this time step.

c. Select the Read button. Fluent will read in the case/data file associated with 5s.

d. Close Fluent.

3. From the Project Schematic, double-click the System Coupling Setup cell (C2):

a. From the outline, select Setup > Analysis Settings.

b. In Properties of Analysis Settings, under Initialization Controls, from the Coupling Initialization

drop-down list, select Step 50, Time 5[s].

c. Optional: Under Execution Control > Intermediate Restart Data Output, set Output Frequency

to None. If this is not done, there will be a second set of restart files output under the Workbench

project.

4. To start solving the coupled analysis restart, right-click the Solution branch in Outline of Schematic

C1: System Coupling, and select Update. The solution progress will be summarized in the Chart Monitor

(starting from 5s) and Solution Information views (also starting from 5s), as well as the Workbench

schematic progress view.

5. Once your solution is complete, select File > Save to save your project.

6. You have now used the Workbench, Fluent, Mechanical, and System Coupling interfaces to complete

this tutorial’s simulation. If you would like to complete the optional steps to run this tutorial using the

command line, continue with Executing the Coupled Analysis from the Command Line (p. 105).

Otherwise, you are now finished Oscillating Plate with Two-Way Fluid-Structure Interaction tutorial.

When you are finished viewing your results, and select File > Save from the main menu, and then

File > Exit to close your Workbench project.




This section describes how to execute the analysis for this tutorial from the command line. In this example,

all executables are run in batch mode (there are no user interfaces or launchers) from a standard install-

ation on a single Windows 64-bit machine.

Note

In order to be able to execute runs from the command line, all executables and dynamic

library dependencies must be properly resolved. For more information, see Executing System

Couplings Using the Command Line.

Preparing the Required Input Files

Runs executed from the command line require input files for each of the executables used in the coupled

analysis.

1. If you have not been creating the input files for the command-line analysis as you worked through the

tutorial, then follow the instructions in Optional: Preparing for a Command-line Run (p. 82) to create

the file structure for the command-line run.

2. If you have not been creating the input files for the command-line analysis as you worked through the

tutorial, then follow directions in the sections referenced below and create the listed input files in the

SystemCouplingOscillatingPlate_CmdLine directory:

a. Create the file structural.dat according to Preparing for a Command-Line Run of the Struc-

tural System (p. 90).

b. Create the file fluidFlow.cas according to Preparing for a Command-Line Run of the Fluent

System (p. 96).

c. Create the file coupling.sci according to Preparing for a Command-Line Run of the System

Coupling System (p. 100).

3. An additional input file is required to execute the Fluent solver in batch mode. In the SystemCoup-lingOscillatingPlate_CmdLine directory, create a journal file named fluidFlow.jou that

contains the following:

file/start-transcript "Solution 1.trn"file set-batch-options , yes ,file/read-case/fluidFlow.cass i i(sc-solve)wcd FLUENTRestart.cas.gzexitok

Running the Analysis

To run the analysis:

1. Open a command window, and from the SystemCouplingOscillatingPlate_CmdLine\Coup-ling_CmdLine subdirectory, run System Coupling service using the following command:




"C:\Program Files\ANSYS Inc\v150\aisol\bin\winx64\Ansys.Services.SystemCoupling.exe" –inputFile ..\coupling.sci

Tip

You may prefer to add the previous command to a batch file.

Now when you run the System Coupling service command, the coupling service starts and creates

the System Coupling Server File (SystemCouplingOscillatingPlate_CmdLine\Coup-ling_CmdLine\scServer.scs ). For details, see Files Generated by Coupling Service (p. 56).

2. Open scServer.scs and review its contents, which will be similar to the following:

12345@yourmachine2SolutionStructuralSolution 1Fluid

where:

• 12345 is the server port

• yourmachine is the host's name

• 2 indicates that two participant connections are expected

• The unique names to be used when starting the structural and fluid flow solvers are, respectively:

"Solution" and "Solution 1". The unique names from the solver(s) are encoded in the coupling service

input file and are reported here along with the names of the systems in the Workbench schematic.

Note this correlation, since the unique names are needed when starting the respective solvers. Note,

as well, that the unique names are determined by Workbench and can vary depending upon the order

in which systems were introduced into the schematic.

3. Copy the fluidFlow.cas file into the FluidFlow_CmdLine subdirectory.

This step ensures that Fluent treats that subdirectory as the run directory, and generates all sub-

sequent case and data files there. By keeping the basic input files separate from the run directories,

you can easily clear or delete the run directories for retries.

4. From a new command window, change to the FluidFlow_CmdLine subdirectory, then run the Fluent

solver by entering the following command:

"C:\Program Files\ANSYS Inc\v150\fluent\ntbin\win64\fluent.exe" 3ddp -hidden -driver null -scport= 12345 -schost= yourmachine -scname="Solution 1" -i ..\fluidFlow.jou>FLUENT.out

5. From a new command window, change to the Structural_CmdLine subdirectory, then run the

Mechanical APDL solver by entering the following command:



"C:\Program Files\ANSYS Inc\v150\ansys\bin\winx64\ANSYS150.exe" -b -scport 12345-schost yourmachine -scname "Solution" -i ..\structural.dat -o ANSYS.out

Note

• In steps 4 and 5 above, you may need to adjust the coupling service port and host (12345and yourmachine, respectively) and solvers' unique names ("Solution" and "Solution 1"

for the Mechanical APDL and Fluent solvers, respectively) based upon information extracted

from the system coupling server file.

• The input file name, structural.dat , will need to be replaced with the name of the

manually-created input file (e.g. mapdl.dat ) if such a file was created to enable a resume

from a Mechanical APDL database file.

Restart Analysis Execution

For the sake of simplicity, the restart analysis uses the same solver and coupling service directories in

which the initial analysis was performed.

Preparing the Required Input Files

In the SystemCouplingOscillatingPlate_CmdLine directory, create the following:

1. Create a restart journal file for the Fluent solver. Name this file fluidFlowRestart.jou , and have

it contain the following:

file/start-transcript "Solution 2.trn" file set-batch-options , yes , rcd/fluidFlow-1-00050.cas(sc-solve) exit ok

Note

The "-1-" in the file name fluidFlow-1-00050.cas represents the run number and

may be different in your system, depending upon how many runs were completed before

writing the .cas file.

2. Create a restart input file for the Mechanical APDL solver. Name this file structuralRestart.dat ,

and have it contain the following:

/batch/solu/gst,on,onantype,4,rest,50,1,continuesolvesavefinish/exit




Run the Analysis

Much as when you ran the initial analysis:

1. Open a command window, change to the Coupling_CmdLine subdirectory, and run the System

Coupling service using the following command:

"C:\Program Files\ANSYS Inc\v150\aisol\bin\winx64\Ansys.Services.SystemCoupling.exe" –inputFile ..\coupling.sci –resultFile scResult_01_000050.scr

2. Open the system coupling server file (scServer.scs ) and note the coupling server’s port and host.

Note that the solvers’ unique names have not changed because they are encoded in the coupling service’s

input file.

3. Change to the FluidFlow_CmdLine subdirectory, and run the Fluent solver by entering the following

command:

"C:\Program Files\ANSYS Inc\v150\fluent\ntbin\win64\fluent.exe" 3ddp -hidden -driver null -scport= 12345 -schost= yourmachine -scname="Solution 1" -i ..\fluidFlowRestart.jou>FLUENTRestart.out

4. Change to the Structural_CmdLine subdirectory, and run the Mechanical APDL solver by entering

the following command:

"C:\Program Files\ANSYS Inc\v150\ansys\bin\winx64\ANSYS150.exe" -b -scport 12345 -schost yourmachine -scname "Solution" -i ..\structuralRestart.dat -o ANSYSRestart.out

Note

In steps 3 and 4 listed above, you may need to adjust the coupling service port and

host (12345 and yourmachine, respectively) and solvers' unique names ("Solution"

and "Solution 1" for the Mechanical APDL and Fluent solvers, respectively) based upon

information extracted from the system coupling server file.

Loading the Results into CFD-Post

To load the Results files into CFD-Post:

1. To start CFD-Post, from the Start menu, go to All Programs > ANSYS 15.0 > Fluid Dynamics > CFD-

Post 15.0.

2. From CFD-Post, select File > Load Results.

3. Open the final CAS file, which will have a name similar to FluidFlow_CmdLine\fluidFlow-1-00100.cas .

4. Again select File > Load Results.

5. In the dialog box that appears, select Keep current cases loaded, and clear Open in new view.

6. Open the file Structural_CmdLine\file.rst . When post-processing results, your structural results

are named after the name of the file they are loaded from. From this command line run, your structural

results will appear under the name “file” (because of file.rst).



7. Proceed to Viewing Results in CFD-Post (p. 100) for instructions on how to post-process the results. When

following these instructions, remember that your command line structural results will appear under the

name ”file”, and not “Structural”.




Tutorial: Heat Transfer from a Heating Coil

In this tutorial you will learn about executing a sequence of one-way thermal transfers in a heat exchanger

using the System Coupling infrastructure.

DetailsFeatureComponent

Steady State ThermalAnalysis SystemsANSYS Workbench

Fluid Flow (Fluent)

System CouplingComponent Systems

External Data

ImportGeometry and Named SelectionsDesignModeler

Defining the physicsSteady State Thermal

Defining the physicsANSYS Fluent

Defining the couplingSystem Coupling

Compare film coefficientsCase ComparisonCFD-Post

Examine temperatures and

temperature distributions

This tutorial includes:


Part 1:Transferring Data from the Steady-State Thermal Analysis to the Fluid Flow Analysis

Part 2:Transferring Data from the Fluid Flow Analysis to the Steady-State Thermal Analysis


In this tutorial, a variety of ANSYS Workbench systems are used to analyze conjugate heat transfer in a

simple heat exchanger.

The heat exchanger involves the coupling of solid and fluid models. The solid model consists of a copper

alloy heating coil and the fluid model consists of an annular region with flowing water that envelops

the coil. A constant heat generation source of 8.72 e+6 W/m3 is specified for the coil and the heat

generated is made to convect away from its surface by water flowing at a nominal speed of 0.4m/s.



The tutorial is divided into two parts. In the first part, the convective heat transfer experienced by the

heating coil is estimated and the steady-state thermal analysis is executed for the solid model. The

resulting temperature from the coil surface is then used to execute the fluid analysis. In the second part

of the tutorial, the thermal analysis for the solid model is also executed, however the convective heat

transfer obtained from the fluid analysis is used instead of the original estimate.

In a case such as the one described here, there are advantages to using one-way data transfer instead

of conjugate heat transfer or two-way analysis. One-way data transfer works well when separate groups

are performing the computational fluid dynamics analysis and the thermal finite element analysis. The

individual solutions are simpler with a one-way analysis than they would be with a two-way coupled

analysis. Another advantage of one-way data transfer is that it provides a more flexible workflow; any

thermal variable of interest can be transferred. Coordinate transformations can also be applied when

using one-way data transfer.

Part 1: Transferring Data from the Steady-State Thermal Analysis to the

Fluid Flow Analysis

This part of the analysis has the following steps:


Adding Analysis and Component Systems

Adding New Materials for the Project


Preparing the Steady-State Thermal Source Data

Using External Data to Access the Steady-State Thermal Source Data

Preparing the Fluid Flow Analysis

Preparing and Executing the Coupled Thermal Analysis

Reviewing Results in CFD-Post


1. Start ANSYS Workbench:

• To launch ANSYS Workbench on Windows, click the Start menu, then select All Programs>ANSYS

15.0>Workbench 15.0.



• To launch ANSYS Workbench on Linux, open a command line interface and enter the path to runwb2 .

For example:

~/ansys_inc/v150/Framework/bin/Linux64/runwb2

The Project Schematic appears with an Unsaved Project. By default, ANSYS Workbench is configured

to show the Getting Started dialog box that describes basic operations in ANSYS Workbench. To

control the display of this dialog box, select Tools>Options from the main menu and go to Project

Management>Startup and select or clear the Show Getting Started Dialog check box.

2. Create a directory where you will store your project (this is your working directory). For example, under

My Documents , create a directory named SystemCouplingHeatingCoilTutorial .

3. Select File>Save.

A Save As dialog box appears.

4. Select the path to your working directory to store files created during this tutorial.

5. Under File name, type SystemCouplingHeatingCoil and click Save.

The project files and their associated directory locations appear under the Files view. To make the

Files view visible, select View>Files from the main menu of ANSYS Workbench.

6. This tutorial uses the geometry file, HeatingCoil.agdb , and a Fluent mesh file, HeatingCoilFLU-ENTMesh.msh, for setting up the project. To access tutorials and their input files on the ANSYS Cus-

tomer Portal, go to http://support.ansys.com/training.

Copy the supplied geometry file, HeatingCoil.agdb , and the mesh file, HeatingCoilFLU-ENTMesh.msh, to the user_files directory that is in the SystemCouplingHeating-Coil_files directory.

By working with copies of the geometry and mesh files in your working directory, you prevent

accidental changes to the original files.

Setting the Units in ANSYS Workbench

To ensure that the units for this project are set correctly, select Units from the top menu bar and confirm

that Metric (kg,m,s,°C,A,N,V) is checked.

Adding Analysis and Component Systems

In ANSYS Workbench, set up an analysis system in order to transfer data from a Steady-State Thermal

system to a Fluid Flow system, as outlined in this section.

1. Drag a Steady-State Thermal system from the Analysis Systems toolbox and drop it onto the Project

Schematic.

2. From the Analysis Systems toolbox, drag a Fluid Flow (Fluent) system onto the Project Schematic

and drop it to the right of the Steady-State Thermal system.

3. You will use the System Coupling infrastructure to obtain data from the Steady-State Thermal system

for use in the Fluid Flow (Fluent) system. From the Component Systems toolbox, drag a System

Coupling system and drop it to the right of the Fluid Flow (Fluent) system.



Part 1:Transferring Data from the Steady-State Thermal Analysis to the Fluid Flow

Analysis

http://support.ansys.com/training

4. Drag the Setup cell from the Fluid Flow (Fluent) system (B4) and drop it onto the Setup cell in the

System Coupling system (C2). That establishes the relationship between the fluid flow and the external

data that is coming in through system coupling.

5. From the Component Systems toolbox, drag an External Data system onto the Project Schematic and

drop it between the Steady-State Thermal system and the Fluid Flow (Fluent) system.

Note that this changes the lettering of the Fluid Flow (Fluent) system from (B) to (C) and the

System Coupling system from (C) to (D).

6. Drag the Setup cell from the External Data system (B2) and drop it onto the Setup cell in the System

Coupling system (D2).

7. Save the project: click Save .

The Project Schematic should appear as shown in Figure 14: Project Schematic of a Fluid Solid Interface,

System Coupling Problem (p. 114).

Figure 14: Project Schematic of a Fluid Solid Interface, System Coupling Problem

The Structural and Fluid systems contain various cells. ANSYS Workbench provides visual indications of

the state of a cell at any given time via icons on the right side of each cell. In Figure 14: Project

Schematic of a Fluid Solid Interface, System Coupling Problem (p. 114), most cells appear with a blue

question mark , indicating that cells need to be set up before continuing the analysis. As these cells

are set up, the data transfer occurs from top to bottom. See Understanding Cell States for a description

of various cell states.

Now the project is ready for further processing. A project schematic such as this with interconnected

systems enables you to perform a multiphysics analysis by adding a new geometry, setting up the

physics of the individual systems (Steady-State Thermal, and Fluid Flow systems in this example), and

also viewing the results.

Adding New Materials for the Project

1. On the Project Schematic, double-click the Engineering Data cell in the Steady-State Thermal system

(A2).

In the tab that appears, you will set the Material Properties for the coil.

2. In the Outline of Schematic A2: Engineering Data window, note that Structural Steel is the first entry

in the Material section. Right-click the empty row at the bottom of the Material section, just below

the Structural Steel entry to add a new material for the project.



3. Select Engineering Data Sources.

4. Click General Materials in the Data Source column of the Engineering Data Sources tab.

5. In the Outline of General Materials section, click the plus sign beside the Copper Alloy option to add

copper alloy material to the project.

6. You now have all the material properties that you need for the project. At the top of your Workbench

window, close the Engineering Data tab to return to the Project Schematic.

7. From the main menu, select File>Save to save material settings to the project.


You will add geometry by importing an existing DesignModeler file.

1. On the Project Schematic, right-click the Geometry cell in the Steady-State Thermal system (A3) and

select Import Geometry>Browse.

2. In the Open dialog box, browse to your working directory, select SystemCouplingHeating-Coil_files >user_files >HeatingCoil.agdb , and click Open.

Preparing the Steady-State Thermal Source Data

You will now define the physics for the steady-state thermal analysis.


To assign the material to the geometry:

1. On the Project Schematic, double-click the Model cell in the Steady-State Thermal system (A4). This

will open the Mechanical application.

2. In the Mechanical application, right-click Project>Model (A4)>Geometry>Part>Container and select

Suppress Body.

3. Click Project>Model (B4)>Geometry>Part>Coil.

4. In the Details of “Coil” view, use the Material>Assignment drop-down box to select Copper Alloy.

Generating the Mesh

You will now define and generate a mesh for the heating coil.

1. In the Mechanical application Outline view, right-click Project>Model (A4)>Mesh and select Insert>Meth-

od.

2. Select the whole coil geometry in the viewer window by clicking on it.

3. In the Details of “Automatic Method” - Method view, click Scope>Geometry>Apply.

4. In the Details of “Automatic Method” - Method view, select Definition>Method>Sweep.

5. Click the box to the right of Definition>Free Face Mesh Type. Select All Tri.




Analysis

6. Click Project>Model (A4)>Mesh to open the Details of “Mesh” view.

7. In the Details of “Mesh” view, select Sizing>Element Size and enter 0.05 .

This creates triangular elements on the source face. These triangular elements then get swept

through the coil body during the Sweep. Quad elements are not used for this case because the

coarse mesh that is used would result in a poor quality mesh on the source face.

8. Right-click Project>Model (A4)>Mesh and select Generate Mesh.

Defining the Physics for the Structural Analysis

In this step, the physics for the steady-state thermal portion of the problem is defined.

Defining the Steady-State Thermal Analysis

1. In the Mechanical application Outline view, click Project>Model (A4)>Steady-State Thermal

(A5)>Initial Temperature.

2. In the Details of “Initial Temperature” view, change Definition>Initial Temperature Value to 250 °C.

3. Right-click Project>Model (A4)>Steady-State Thermal (A5) and select Insert>Internal Heat Generation.

4. Select the coil body in the viewer window.

5. In the Details of “Internal Heat Generation” view, click Geometry>Apply.

6. In the Details of “Internal Heat Generation” view, change Definition>Magnitude to 8.72e6 W/m3.

This is the source for the steady-state thermal calculation.

7. In this step you will introduce a convection boundary condition to allow the heat to escape from the

area around the coil. The convection boundary condition is applied to the outer coil surface, not to the

ends. The heat that was introduced in the previous step will be dissipated due to convection.

In the Mechanical application Outline view, right-click Project>Model (A4)>Steady-State Thermal

(A5) and select Insert>Convection.

Convection values will reflect the heat removal from the coil surface.

8. In the Details of “Convection” view, change Scope>Scoping Method to Named Selection.

9. In the Named Selection drop-down box, select CoilSurface.

10. Change Definition>Film Coefficient to 1000 W/m2·°C.

11. Change Definition>Ambient Temperature to 30°C.

The heat transfer (film) coefficient value should be approximately 1000 W/m2·°C. This will be the

estimate that you use for this part of the tutorial. In a later part of this tutorial, you will run the

CFD analysis and compare the estimated number to the calculated number for the heat transfer

coefficient value. At that time, you will replace the estimated heat transfer coefficient value with

the full set of heat transfer coefficient values that are calculated from the fluid dynamics side.

12. To define the fluid solid interface, in the Mechanical application Outline view, right-click Project>Model

(A4)>Steady-State Thermal (A5) and select Insert>Fluid Solid Interface.



13. In the Details of “Fluid Solid Interface” view, change Scope>Scoping Method to Named Selection.

14. In the Named Selection drop-down box, select CoilSurface.

15. In the Export Results drop-down box, select Yes. This setting will make Mechanical export the static

results to an ANSYS External Data file (the .axdt file).

The .axdt files are generated from the results on defined fluid solid interfaces. These files will be

used to transfer thermal data from ANSYS Mechanical to ANSYS Fluent when you are using External

Data and System Coupling (this is the method used in this tutorial).

16. In the Mechanical application Outline view, right-click Project>Model (A4)>Steady-State Thermal

(A5)>Solution (A6) and select Insert>Thermal>Temperature.

17. In the Mechanical application Outline view, right-click Project>Model (A4)>Steady-State Thermal

(A5)>Solution (A6) and select Insert>Thermal>Total Heat Flux.

18. Click File>Save Project.

Executing the Structural Analysis

To create the temperature and heat flux distribution solutions, click the Solve button which

is located in the main toolbar of the Mechanical application.

Post-Processing the Structural Analysis Results

When the solution is complete you will look at the temperature and total heat flux distribution results:

1. To look at the temperature distribution, in the Mechanical application Outline view, click Project>Model

(A4)>Steady-State Thermal (A5)>Solution (A6)>Temperature.




Analysis

Figure 15: Temperature of the Coil

2. To look at the total heat flux distribution, in the Mechanical application Outline view, click Project>Model

(A4)>Steady-State Thermal (A5)>Solution (A6)>Total Heat Flux.



Figure 16: Total Heat Flux Distribution on the Coil

In the Messages view, just under the viewer window, there will be an Info message that states,

"The thermal results at the Fluid Solid Interface(s) have been written to the solver files directory."

This tells you that the .axdt file has been created. You now have an ANSYS External Data file

(.axdt file) that can be brought into External Data. This file contains the Temperature and Heat

Flow values exported from the Fluid Solid Interface region that you defined. This file will be imported

into External Data to provide thermal boundary conditions for Fluent via the System Coupling

component.

3. Click File>Save Project and File>Close Mechanical.

Using External Data to Access the Steady-State Thermal Source Data

You can access the ANSYS External Data file (.axdt file) as follows:

1. In the Files window, scroll down to find the fsin_1.axdt file.

2. Right-click the file path under the Location column for the fsin_1.axdt file and select Copy. This

transfers the file path to your clipboard.

3. On the Project Schematic, double-click the Setup cell in the External Data system (B2).




Analysis

4. Under Location in the Outline of Schematic section, click the button and select Browse. Use Ctrl-v

to paste the location of the fsin_1.axdt file into the File Name field.

5. Press the Enter key on your keyboard to open the directory that contains the fsin_1.axdt file.

6. Select the fsin_1.axdt file and click Open.

All the information about the external data for this project has been automatically entered into

the appropriate data sections. In the Properties of File section, the Value of the Format Type is

AXDT. The Table of File section summarizes the x, y and z coordinate data that appear in the

Preview of File section. There are also temperature values in Celsius and heat rate in Watts that

have been imported from the fsin_1.axdt file. You can scan this data to ensure that it seems

reasonable for this project.

7. Close the External Data tab to return to the Project Schematic.

8. On the Project Schematic, right-click the Setup cell in the External Data system (B2) and select Update.

Preparing the Fluid Flow Analysis

To prepare the fluid flow analysis:

Importing the Mesh for the Fluid Flow Analysis

You will add the mesh to be used in the Fluent analysis by importing an existing Fluent mesh file.

1. In the ANSYS Workbench Project Schematic, right-click the Mesh cell in the Fluid Flow (Fluent) system

(C3) and click Import Mesh File>Browse.

2. Browse to your working directory, select SystemCouplingHeatingCoil_files>user_files>HeatingCoilFLUENTMesh.msh, and click Open.

You will notice that the Geometry cell is automatically deleted and the Mesh cell is renamed to

Imported Mesh.

Defining the Physics for the Fluid Flow Analysis

At this stage of the analysis, you will define the physics for the fluid flow portion of the problem.

1. Double-click the Setup cell in the Fluid Flow (Fluent) system (C3) to start Fluent.

2. In the Fluent Launcher, select Double Precision. Click OK.

The mesh file is automatically loaded into the Fluent session.

3. Select Solution Setup>Models>Energy>Edit. Check the Energy Equation check box and click OK.

4. In the Models setting, click Viscous – Laminar>Edit. Select k-epsilon (2 eqn) for the Model and

Scalable Wall Functions for the Near-Wall Treatment. Click OK.

5. Select Solution Setup>Materials>Fluid.

6. Click the Create/Edit button.

7. Click the Fluent Database button.



8. In the Fluent Fluid Materials section, select water-liquid (h2o<l>).

9. Click the Copy button to add water to this problem and click Close.

10. In the Create/Edit Materials panel, click Change/Create and Close.

11. Select Solution Setup>Cell Zone Conditions>Edit.

12. In the Fluid panel, change Material Name to water-liquid. Click OK.

13. Select Solution Setup>Boundary Conditions.

14. Before you select a zone, select the Highlight Zone check box in order to display only the selected

zone in the viewer.

15. Select coilsurface>Edit.

16. In the Wall panel, in the Thermal tab, set the Thermal Conditions to via System Coupling. Click OK.

This boundary is now marked as one that will participate in couplings. It will be able to accept

either temperature or heat flow data.

17. Select inflow.

18. Change the Type to velocity-inlet and click Yes to accept this change.

19. In the Velocity Inlet panel, set the Velocity Magnitude to 0.4 and click OK.

20. Select outflow.

21. Change the Type to pressure-outlet and click Yes to accept this change.

22. In the Pressure Outlet panel, verify that the Gauge Pressure is 0. Click OK.

23. Select Solution>Solution Methods and set the Scheme to Coupled.

24. Select Solution>Monitors>Residuals, Statistics and Force Monitors>Residuals - Print, Plot and click

Edit.

25. In the Residuals Monitors panel, under Equations, change Absolute Criteria for energy residual from

1e-06 to 1e-05 .

26. Click OK.

In this problem, energy residuals level off around 8e-06. This step ensures that Fluent terminates

once this level of convergence is reached during the coupled analysis.

27. Select Solution>Run Calculation and set the Number of Iterations to 200 .

28. Click File>Save Project to pass the changes to Workbench.

29. Now that the physics is defined, close Fluent.

The next step is to set up the coupled thermal analysis.




Analysis


1. In the ANSYS Workbench Project Schematic, double-click the Setup cell in the System Coupling system

(D2).

2. Click Yes in the pop-up window to read the upstream data.

3. In Outline of Schematic D1: System Coupling, select System Coupling>Setup>Participants >External

Data>Regions>File1.

This is the .axdt file that was copied into External Data in the Using External Data to Access the

Steady-State Thermal Source Data (p. 119) section.

4. In Properties of Region: File1, right-click Topology>Output>File1:Temperature1 and select Create

Data Transfer.

5. In Outline of Schematic D1: System Coupling section, select System Coupling>Setup>Data Trans-

fers>Data Transfer.

6. In Properties of Data Transfer : Data Transfer section, in Target>Participant, select Fluid Flow

(Fluent).

7. In Target>Region, select coilsurface.

8. In Target>Variable, select temperature.

9. Click File>Save.

Note

For one-way steady thermal coupled analyses, it is good practice to use one coupling

iteration per run. This can be done by selecting Analysis Settings in the tree view and

changing Maximum Iterations to 1 in the details view. However, in this tutorial, default

settings will be used.

10. Click on the Project tab in Workbench to return to the Project Schematic, keeping the System Coupling

tab open.

11. From the Project Schematic, right-click the Fluid Flow (Fluent) system’s Solution cell (C4) and select

Properties. In the Properties view that appears in Workbench, check Solution Monitoring. This setting

will allow you to monitor Fluent’s solution from Workbench.

Right-click the Fluid Flow (Fluent) system’s Solution cell (C4) and select Show Solution Monitoring.

A new tab opens with the solution monitor. When you solve your analysis using System Coupling,

use this tab to watch Fluent solve the fluid part of this analysis.

12. Click on the System Coupling tab in Workbench to return to the system coupling interface.

13. In Outline of Schematic D1: System Coupling, right-click System Coupling>Solution and select Update.

This starts the coupled analysis. Fluent connects up to the coupling service and will run end-to-

end. Fluent will accept external data and will run through its full convergence. Solution progress



is summarized in the Scene Chart Monitor : Chart and Solution Information : System Coupling

views.

14. In Outline of Schematic D1: System Coupling, right-click System Coupling>Solution>Chart Monitors

and select Create Convergence Chart to create a new convergence chart.

15. Right-click the new Chart 2 that appears and select Add Variable>External Data>Data Trans-

fer>Value>Average.

16. Right-click the same chart again and select Add Variable>Fluid Flow (Fluent)>Data Transfer>Value>Av-

erage.

The chart shows the difference between the average nodal temperature values in Kelvin, transferred

from the source region to the target region. Notice that the source and target values differ by ap-

proximately 11 degrees. This difference is due to mismatching of the nodes on the source and

target sides.

17. Close the System Coupling tab to return to the Project Schematic.

Reviewing Results in CFD-Post

You will view three graphical results of the project in CFD-Post.

1. In the ANSYS Workbench Project Schematic, double-click the Results cell in the Fluid Flow (Fluent)

system (C5) to start CFD-Post.

2. From the CFD-Post toolbar, click and select Plane.

3. Click OK to accept the default name of Plane 1 .

4. In the Details of Plane 1 section, in the Geometry tab, set the Method to ZX Plane.

5. In the Color tab, set the Mode to Variable and the Variable to Temperature.

6. Set the Range to User Specified, the Min to 300 K, and the Max to 305 K.

7. Click Apply.

8. Click the y axis on the Viewer triad.

Figure 17: Advection of Heated Water Out of the Heat Exchanger (p. 124) shows the thermal

boundary layer around the coil surface and illustrates how the warmed-up fluid is being advected

out of the heat exchanger. The full temperature range is much larger due to temperature extremes

on a small fraction of the surface. By neglecting those extreme temperatures, more colors are used

over the range of interest.




Analysis

Figure 17: Advection of Heated Water Out of the Heat Exchanger

9. For the next view, disable the plane view by deselecting the Outline>User Locations and Plots>Plane1

check box.

10. Select the Outline>Cases>FFF>part container>coilsurface check box.

11. Right-click the coil surface in the Viewer and select Color>Wall Heat Transfer Coefficient.

Earlier in the tutorial, the heat transfer (film) coefficient value was estimated at approximately 1000

W/m2·°C. This is slightly lower than with the average calculated value on the coil surface in Fig-

ure 18: Wall Heat Transfer Coefficient on the Coil Surface (p. 125).

Note that there is variability in the distribution of the heat transfer coefficient on the coil surface.

This distribution will be explored in the second part of this tutorial where you will replace the es-

timated heat transfer coefficient value with the full set of heat transfer coefficient values that are

calculated from the fluid dynamics side. The data from the first part of the tutorial will be exported

from CFD-Post and brought into a system coupling analysis of a steady state thermal system.



Figure 18: Wall Heat Transfer Coefficient on the Coil Surface

12. For the next view, right-click the coil surface in the Viewer and select Color>Wall Adjacent Temperature.

In the Defining the Steady-State Thermal Analysis (p. 116) section, we estimated that the ambient

temperature of the coil surface would be approximately 30°C. Figure 19: Wall Adjacent Temperature

on the Coil Surface (p. 126) shows that the calculated wall adjacent temperature is close to this

value with some variation. In the second part of this tutorial, we will transfer the data of the tem-

perature distribution over to the structural side.




Analysis

Figure 19: Wall Adjacent Temperature on the Coil Surface

Part 2:Transferring Data from the Fluid Flow Analysis to the Steady-State

Thermal Analysis

This part of the analysis has the following steps:

Exporting the Data

Adding Additional Analysis and Component Systems

Using External Data to Access the Fluid Flow Source Data

Preparing the Steady-State Thermal Analysis


Reviewing Results in the Mechanical Application

Exporting the Data

Export results from the first part of the tutorial.

1. If you are not already in CFD-Post, in the ANSYS Workbench Project Schematic, double-click the Results

cell in the Fluid Flow (Fluent) system (C5) to start CFD-Post.



2. Click File>Export>Export External Data File.

3. In the Export External Data File panel, confirm that the File path is pointing to user_files/export.axdt .

4. Select coilsurface for the Location.

5. In the Select Recommended Variables box, select HTC and Wall Adjacent Temperature.

6. Click Save and close CFD-Post.

Adding Additional Analysis and Component Systems

The physics for this steady-state thermal system is identical to the physics in the first part of this tutorial,

except that the data for the convection boundary condition will be obtained from the output from the

first part of this tutorial through system coupling.

1. In order to create a copy of the first system, right-click the Setup cell (A5) in the Steady-State Thermal

system and select Duplicate. The setup for this duplicate system (E) is identical to the setup of the A

Steady-State Thermal system. Duplicating from the Setup cell in this way produces a new system with

shared Engineering Data, Geometry and Model. The existing Setup cell state is copied to the new

system.

2. From the Component Systems toolbox, drag a System Coupling system and drop it to the right of

the Copy of Steady-State Thermal system. This will provide data to the steady-state thermal system.

3. Drag the Setup cell from the Copy of Steady-State Thermal system (E5) and drop it onto the Setup

cell in the System Coupling system (F2).

4. From the Component Systems toolbox, drag an External Data system onto the Project Schematic and

drop it to the left of the Copy of Steady-State Thermal system.

Note that this changes the lettering of the Copy of Steady-State Thermal system from (E) to (F)

and the System Coupling system from (F) to (G).

5. Drag the Setup cell from the External Data system (E2) and drop it onto the Setup cell in the System

Coupling system (G2).



Part 2:Transferring Data from the Fluid Flow Analysis to the Steady-State Thermal

Analysis

Figure 20: Project Schematic of a Fluid Solid Interface, System Coupling Problem Part 2

Using External Data to Access the Fluid Flow Source Data

The fluid flow source data was generated in the first part of this tutorial. You will provide the path to

this data so that it can be used in the analysis.

1. If the Files window is not already open, select View>Files.

2. Click the down arrow next to Type in the title bar of the Files window to sort the type of files in ascend-

ing order.

3. To copy the file path for the source data, in the Location column, right-click the file path for the export.axdt file and select Copy.

4. In the Project Schematic, double-click the Setup cell in the second External Data system (E2).

5. In the Outline of Schematic section, under the Location column, click the ellipsis button and select

Browse. Paste the data source file path into the File Name section of the Open File(s) window. Select

the export.axdt file and click Open.

6. Close the External Data tab to return to the Project Schematic.

7. In the Project Schematic, right-click the Setup cell in the External Data system (E2) and select Update.

Preparing the Steady-State Thermal Analysis

1. Double-click the Setup cell in the Copy of Steady-State Thermal system (F5).

2. In the Outline view of the Mechanical application, in the Steady-State Thermal 2 (F5) section, a duplicate

of the manually-specified Convection condition is still present. Remove this by right-clicking and selecting

Delete.



In the first part of this tutorial, the Fluid Solid Interface was used to flag a region so that an .axdtfile was created and temperature values and heat rates were output. In the second part of this tu-

torial, the Fluid Solid Interface will be used to receive data from system coupling as well as to

create an .axdt file.

3. Close the Mechanical application.

4. Right-click the Setup cell in the Copy of Steady-State Thermal system (F5) and select Update.


1. Double-click the Setup cell in the System Coupling system (G2). Click Yes to read the upstream data.

2. You will set up the data transfer. In the Outline of Schematic G1: System Coupling window, Ctrl-select

Fluid Solid Interface and File 1. Right-click File 1 and select Create Data Transfer to automatically

create a pair of data transfers.

Data Transfer is for the heat transfer coefficient and Data Transfer 2 is for the reference temper-

ature.


4. Right-click the Solution section and select Update. This will draw the data from the external data system

and provide it to the Mechanical application.

5. After the solution has finished, close the System Coupling tab to return to the Project Schematic.

6. Right-click the Results cell in the Copy of Steady-State Thermal system (F7) and select Update.

Reviewing Results in the Mechanical Application

1. Double-click the Results cell in the Copy of Steady-State Thermal system (F7) to open the Mechanical

application.

2. To compare the results from the first part of the tutorial with those from the second part, split the

viewer window into two parts. Click the Viewport icon in the top menu bar and select Vertical View-

ports.

3. Click in the left viewport and then in the Outline view, click Steady-State Thermal (A5)>Solution

(A6)>Temperature.

4. Click in the right viewport and then in the Outline view, click Steady-State Thermal 2 (F5)>Solution

(F6)>Temperature.




Analysis

The left view now shows the original, uncoupled case and the right view is the coupled result.

5. To synchronize the two views, click the Manage Views icon in the top menu bar.

6. The Manage Views window appears in the lower left part of the Mechanical application window. Click

in the left viewport and click the Create a View icon, .

7. Click in the right viewport, select View 1 and click the Apply a View icon, .

8. To allow a better comparison of the two sets of results, both the scales should be changed to the same

values. Double-click the second-lowest value in the colored legend and change it to 200 and change

the second-highest value in the colored legend to 1600. Do this in both the left and right viewports.

Figure 21: Comparison of Coil Temperature Contours from the First and Second Parts of the

Tutorial

As noted at the end of the first part of the tutorial, the constant heat transfer coefficient value applied

in the thermal analysis of the coil under-predicts the spatially-varying values generated by the fluid

analysis. Qualitative and quantitative differences are consequently observed between thermal analyses

of the coil in the first and second parts of the tutorial. When the larger, spatially-varying heat transfer



coefficient values are applied, the resulting temperature values decrease appropriately and temperature

variations occur over the coil surface. For example, the lowest temperatures are observed on the lower,

side portions of the coil cross-section due to increased convective cooling in those regions. Convective

cooling decreases on the lower and upper portions due to flow stagnation and recirculation, respectively.

The effect of the larger, spatially-varying heat transfer coefficient values on the heat flux solution values

from the thermal analyses corroborate these observations.

1. To compare the total heat flux, select the left viewport and click Steady-State Thermal (A5)>Solution

(A6)>Total Heat Flux.

2. Select the right viewport and select Steady-State Thermal 2 (F5)>Solution (F6)>Total Heat Flux.

Figure 22: Comparison of Coil Total Heat Flux Contours from the First and Second Parts of

the Tutorial

3. When you are finished viewing your results, select File>Save Project from the main menu, and then

File>Close Mechanical. Select File>Exit to close your Workbench project.




Analysis

Index

Aanalysis settings, 9

best practices, 12

Analysis Settings field, 9

Analysis Type property, 9

Bbest practices, 73

Cchart monitors, 29

CHT (Conjugate Heat Transfer) example, 111

co-simulation participant

controlled by the system coupling service, 1

co-simulation participant sequencing, 76

co-simulation participant stability, 76

ramping, 76

solution stabilization, 76

command line options, 34

command line usage, 33

conjugate heat transfer

example, 111

coupled analyses

debugging using graphical monitor output, 75

debugging using text based monitor output, 74

restarting, 35

coupled solution execution time

using sequencing to reduce, 77

coupling initialization, 10

coupling service

files used by, 55

DData Transfers

creating, 14

data transfers, 16, 44

algorithms, 46

profile preserving, 47

conservative profile preserving, 47

interpolation algorithms, 53

mapping algorithms, 46

bucket surface, 48

General Grid Interface (GGI), 51

postprocessing interpolated data, 53

ramping, 53

under-relaxation, 54

pre-processing algorithms, 45

Debug Output control, 20

debugging two-way coupled analyses, 73

using graphical monitor output, 75

using text based monitor output, 74

duration controls, 10

Duration Defined By property, 10

EEnd Time, 10

examples

CHT, 111

conjugate heat transfer, 111

heat exchanger, 111

solid region, 111

steady state simulation, 111

transient mechanical analysis, 87

Ffluid-solid interactions, 79

Ggeneral analysis type, 12

Hheat exchanger example, 111

Iinitialization controls, 10

input file, 58

Llog file, 20

scLog.scl, 65

Mmaximum iteration, 11

minimum iteration, 11

OOutline view, 8

output

intermediate, 22

output frequency

all steps, 23

at step interval, 23

none, 22

Pparticipant

exchanges data in a coupled analysis, 1

summary, 13

performance

improving in system coupling, 77



Properties view, 8

Rramping, 53

region

part of the topology of a coupling participant, 13

restart data

intermediate, 22

restart points, 10

results file

scResults_##_######.scr, 58

SScene view, 9

sequencing of solution steps, 20

sequential solutions, 20

server file

scServer.scs, 56

service input file

scInput.sci, 55

service log file

scLog.scl_, 57

service overview, 41

service shutdown file

scStop.stop, 56

simulation example

steady state, 111

simultaneous solutions, 20

solid

region example, 111

Solution Information view, 9

solvers

coupling two-model interactions, 80

steady state simulation example, 111

Step Controls property, 11

step size, 11

structural deformations

modeling, 79

structural properties

assigning the material to geometry, 87

system coupling

analyze decoupled systems first, 73

context menus

Setup cell, 23

Solution cell, 32

overview, 1

workspace, 7

system coupling management, 41

convergence management, 43

evaluating convergence, 43

inter-process communication, 41

process synchronization, 41

system coupling states

Setup cell, 23

Solution cell, 32

Ttransient analysis type, 13

transient mechanical analysis

example, 87

Uunder-relaxation, 54

Vview

convergence plots, 9

outline, 8

properties, 8

scene, 9

solution information, 9


Index

System Coupling Users Guide

Documents

Transcript of System Coupling Users Guide