ANSYS CFD v16 Update Seminar - CAE Associates · PDF fileparts on fluid or solid side, GUI...

© 2015 CAE Associates

ANSYS CFD v16

Update Seminar

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Outline

ANSYS CFD Demo — CFX — Fluent — Icepak

ANSYS CFX v16 ANSYS Fluent v16

ANSYS Icepak v16

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CFX, Fluent, Icepak demo

CHT setup — Flow domain and solid parts — Automatic fluid-solid interface generation

Internal fan model

— Detail 3D fan blade geometry not modeled — Pressure jump condition

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Flow domain and solid parts

heat sink

transformer

fan

flow domain

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CHT with Fan Model

CFX — Pros : Easy to use, better tree outline structure, easy to identify

parts on fluid or solid side, GUI graphics to indicate which part is selected, auto contact detection for fluid-solid and solid-solid interfaces, multiple units available for each input, fan curve can be implemented

— Cons : need to write a CEL to implement fan swirl angle if needed

Fluent — Pros : auto contact detection for fluid-solid and solid-solid

interfaces, fan specific boundary page, easy to implement fan swirl angle if needed, fan curve can be implemented

— Cons : all fluid-solid interfaces are lumped into boundary condition page, takes effort to identify the parts (especially on a complex problem)

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CHT with Fan Model

Icepak

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Outline



ANSYS Icepak v16

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HPC Performance Improvements

Background — Dramatic HPC scalability

advances were previously implemented, and required additional expert parameter settings for activation

R16 incorporates numerous HPC improvements and changes, to deliver excellent scalability ‘out-of-the-box’

— Note change: coupled partitioning is the new default in R16

• Can change convergence behavior!

Default HPC scaling on a transient water turbine simulation with 40M

nodes; benchmark in collaboration with Voith Hydro and HLRS in Stuttgart

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I/O: File Writing with MPICH Background

• File writing time found to be excessive and not scaling on some systems identified as an issue with MPICH-based MPI

• Affected Cray ES mode, Intel MPI and Microsoft’s MS-MPI

• IBM Platform Computing MPI not affected

R16 includes a dramatic

reduction in the file write time with MPICH-based MPI

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Turbulence Modeling

Background — Accurate CFD simulations

require accurate prediction of turbulent flow phenomena

New turbulence capabilities include:

— BSL-ω model — Stress-Blended Eddy

Simulation (SBES) model (β)

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Reattachment Modification

Background — RANS models may produce

exaggerated separation zones, at least when separation onset is correctly predicted

— Thought to be an inherent limitation of RANS models

R16 includes the release of an

option for the SST model to improve prediction of the re-attachment location

— Note: effect can be reduced with severe mesh refinement

Red arrows show the re-attachment location predicted with and without the

modification on a validation test case, and how it significantly improves agreement with the experimentally-measured re-

attachment location (black arrow)

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Improved Mass Flow Rate Specification

Background — Mass flow rate boundary

condition specified for meshed boundary area, not for machine

— Change in blade count can lead to inconsistent specified flow rate

R16 adds new Mass Flow Rate Area option with “Total for All Sectors”, allowing machine mass flow rate to be specified directly

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Improved Mass Flow Rate Specification

Total for All Sectors area

Mesh sector boundary area

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Fourier Transformation for Single Stage TRS Background

— Fourier Transformation Transient Rotor/Stator (FT-TRS) method was a beta feature in previous releases. Since its initial beta release, it has gone through a series of improvements, including accuracy and speed.

In R16 FT-TRS is a released feature — FT-TRS is best used on large pitch ratio

single stage turbomachines where the use of other pitch-change models is not possible

— FT-TRS supports simulations with incompressible fluids in rotating machines such as pumps

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● Beta: Extension to FT-TRS functionality to handle asymmetric flow situation. Connect rotor to 360 deg. domain

‒ Impeller in a Vaneless volute ‒ Fan in a crosswind

TBR in R16.0 FT Method

FT-TRS

FT-TRS

Reference FT

Impeller in Vanless Volute

Compressor off-design performance • Fan in crosswind • Boundary layer ingestion

• Ground vortex ingestion

• Inlet swirl distortion

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● Beta: Modeling multistage compressor/turbine with combination of TT-TRS and other interfaces (i.e. PT or Stage)

‒ Aerodynamic performance

‒ Position TT-TRS where the shock cross the interface. It will help in obtaining correct flow rate

TBR in R16.0 TT Method

IGV R1 S1 R2 S2

TT TT PT PT

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● Beta: Single Sided TT-TRS (STT) • Modeling multistage compressor/turbine

with combination of TT-TRS and STT-TRS • Further improvement to aerodynamic

performance prediction

TBR in R16.0 TT Method

STT

R1 S1

TT PT

IGV

TT

R2

TT

Entropy contour reconstruction Single passage per row TT/STT model

Entropy contour Reference full-wheel model

TT TT STT STT

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Provide Harmonic Forced Response Analysis in MAPDL

● Background — R15 provided export of pressure

harmonics for Mechanical cyclic Mode Superposition, but did not support user specification of the engine order to export

● CFX can now export pressure harmonic for:

— Arbitrary user-specified engine order (EO) from blade row interaction

— Blade vibration frequency from blade flutter analysis

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More Accurate Meridional Averaging

Background — Undefined values on a polyline

could skew quantities like meridional averages and there were limitations with TBR data instances

Meridional length averaging in R16 properly handles undefined points and works correctly with TBR data instances

R15 (top) shows discontinuities in meridionally-averaged pressure, much

improved in R16 (bottom)

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Precision Control for Auto-Annotation

Background — Animations of transient

with display of time could lead to ‘jumpy’ text output, depending on given time value

R16 adds user control for

the number precision, giving better and cleaner annotation display in the viewer

— Applies to time value and other numerical quantities

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Outline



ANSYS Icepak v16

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Graphical User Interface

R16 introduces a new tree-based UI

— Branches of the tree provide an overview of the case set up

— New right-click menus allow quick access to most commonly used functionality

— Ability to save contour and vector definitions

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Workbench Integration

Background — Continued development

of capabilities that extend parametric simulation capabilities for Fluent in Workbench

R16 fully releases ability

have to multiple upstream mesh systems with Fluent

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User Interface Customization

Background — Many users have wanted to

user scheme and create custom user interface components, but little information has been available

New documentation for creation of custom user interface

— Instructions on how to use scheme to customize Fluent

— Examples for adding menu items and dialog boxes

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Extreme Parallel Scalability

Background — Continuously strive to improve solution scalability and stay

ahead of the competition R16 scales better than any other commercial CFD code

— 830 million cells — 86% efficiency at 36k cores, 1024 cores as base

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HPC Performance Improvements

Background — Many cases, particularly

unsteady moving mesh simulations, have suffered poor performance in parallel

Performance has been

improved for simulations that include

— Wall distance calculations — Sliding mesh

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Poor Mesh Numerics

Background — Users need to be able to

solve on efficiently generated meshes- often this means accepting poorer quality cells in some regions

Improved handling of poor

quality meshes — New cell quality-based

criteria for use of special ‘poor mesh’ numerics

— Improved user controls

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Polyhedral Conversion

Background: — Performance bottlenecks with

polyhedral conversion have been a common complaint from customers with large cases

Improvements include

— Removed parallel bottleneck for large meshes

— Improved parallel performance of optimization step

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Mapped Mesh Interfaces

Background — Robust methods are

needed to handle coupled boundaries in complex models

New mapped interface

option for coupled walls between zones

— Fluid-solid and fluid-fluid — Supports conjugate heat

transfer and radiation

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Acoustics Modeling

Background — Cabin noise

prediction is a key application for the automotive industry

Expanded capabilities include

— Frequency band post processing of sound sources

— 1-way coupling to harmonic and response analysis in ANSYS Mechanical (β)

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• 87 M tet/prism mesh • 15 prism-layers • Orthogonal Quality: 0.005 (use PMN)

Acoustic analysis – SAE bluff body

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Acoustics Pressure Loading in Frequency Domain

Freq. 455 Hz Freq. 455 Hz

Freq. 1575 Hz Freq. 1575 Hz

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Simulated SPL vs Experiments

3 4 5 6 7 8

9 10 11 12 13 14

15 16 17 18 19 20

22 23 24 25 26 21

Freq. res= 10.8Hz or T=0.0925s Welch Average Periodogram, 50% overlap

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CFD Analysis Information

• Startup: • Ramping down the time-step from 1e-03s to 3e-05s for 0.35s

physical time • Sampling:

• 9,200 time-steps • dt = 3e-05 • Many tests: 2-4-8 iter per timesteps • T sampling = 0.2634 s • Max freq. = 16.67 kHz • Min (freq.-res.)= 3.6 Hz

• Computational Info:

• ~263h for 9,200 time-steps on 168 cores (Intel Xeon 2.93 GHz, SLES 11 SP1, 2016 GB RAM available (~300 GB used)

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Compressible Multiphase Flows

Background — Solver robustness

typically a bigger issue as physics become more complex

New numerical

treatments — Improved start-up and

run-time robustness for compressible multiphase flows

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Free Surface Flows (VOF)

Background — Broad range of free surface

flow applications – many requests for better ease-of-use and accuracy

VOF modeling adds a number

of enhancements in R16 — Enhanced Usability — More intuitive set up, less

error-prone — Enhanced numerics — Modified compressive scheme — Improved interface capturing

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Eulerian Multiphase Speed

Background — Long transient solution

times for multiphase simulations

Significant speedup for

Eulerian multiphase problems

— Non-Iterative Transient Advancement (NITA) is now available for multiphase flows

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System Coupling Improvements

Background: — Extend the range of

applications that can modeled using system coupling

Support for porous

zones with FSI — Porous media and

porous jumps are both supported

— 1 and 2-way coupling

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Wall Film Modeling

Background — Wide demand to expand

range of application for wall film models

LWF

— UDF for impingement and splashing

— Energy transfer from film to wall

— New film boiling model

EWF — Support for periodic

boundaries

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Wall Film Validation

• Cross Flow Injection • Primary Breakup • Secondary Breakup • Film Formation • Film Splashing, Stripping & Separation

Arienti et. Al. LES Simulations Arienti et. al. data and LES Simulations

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0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 Fi

lm T

hick

ness

(um

) Distance along Filmer (mm)

LWF

EXPT.

Comparison of wall film height

Cross-flow Velocity of Air: 82 m/s Jet Velocity: 12.7 m/s

Wall Film Validation

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Plotting Fluent Boundary Face Values

Background — Using interpolated nodal

values for contour plots may not always sufficiently accurately reflect boundary values applied in Fluent

R16 allows you to choose to

use face values from Fluent in the generation of contour plots, to create plots that are fully consistent with boundary values applied in the solver

Face Values

Interpolation from Nodes

Example of difference on a polyhedral mesh

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Outline



ANSYS Icepak v16

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Maxwell to Icepak Coupling

• Maxwell Icepak • Both one way or

two way coupled • Heat flow density q”

is accurately mapped from Maxwell to Icepak

Planar transformer

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Cold plate & Busbar Assembly

Cold plate

Busbars

Fins

• Natural convection with side walls & top, bottom modeled as openings

• Heat generated in Busbar is carried away

by liquid cold plate system

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Server - Graphics Card

• Ease of use with auto settings of power map thresholds

• Icepak import preview and filter enhances workflow with Icepak

• Icepak trace modeling successfully validated against explicit trace models for simple non-standard mcm/anf based packages

• Explicit trace modeling for complete BGA and PCB not yet practical – successful with very high refinement of Icepak trace modeling instead

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ANSYS CFD v16 Update Seminar - CAE Associates · PDF fileparts on fluid or solid side, GUI...

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