FloTHERM Basic Training - 易富迪科技 · chassis —For the space above the chassis, allow for...

FloTHERM Basic Training

Jay Chien易富迪科技 / EFD Corporation http://www.efd.com.tw

LECTURE 1 INTRODUCTION TO FloTHERM

Lecture Agenda

• What is CFD?• What does FloTHERM do?• How does FloTHERM work?• Creating a FloTHERM model• Starting FloTHERM• Application windows• Creating and editing geometry• Help

What Is CFD?

“Computational Fluid Dynamics or CFD is the analysis of systems involving fluid flow, heat transfer and associated phenomena, such as chemical reactions by means of computer-based simulation”

Versteeg & Malalasekera, “An Introduction to Computational Fluid Dynamics: The Finite Volume Method”

FloTHERM – What Does it do?

• Solves airflow and heat transfer problems in electronics equipment

• Airflow is the movement of air caused by natural (buoyancy) or mechanical (fans) forces

• Heat transfer is the transfer of thermal energy because of a temperature difference

• Three modes exist…

Conduction – which is the transfer of heat through a solid or stationary fluid

Convection – which involves the transfer of heat from a surface to a moving fluid

Radiation – which involves the transfer of heat between two or more surfaces

1. Conduction through a solid or a stationary fluid

Heat Flow

T1 > T2 Q = kA(ΔT/Δx)

2. Convection from a surface to a moving fluid

Moving Fluid T2

Surface T1

Heat Flow

T1 > T2Q = hAΔT

3. Radiation heat exchange between two surfaces

Surface T1

Surface T2

T1 > T2

Q = εσA(Thot4 -Tcold

• FloTHERM divides both the solid and fluid spaces into many small grid cells and solves conservation equations within each cell.

How Does FloTHERM Work?

• Airflow and heat transfer are governed by the following equations:• Conservation of Mass (continuity)• Conservation of Momentum• Conservation of Energy

• These equations are known as the Navier-Stokes Equations

• The Navier-Stokes Equations can be expressed in a common form

• Partial differential equations, therefore can not be solved in “raw” form

SgradVdivt

transient + convection – diffusion = Source

• Need to use the Finite Volume Approach• Taylor series expansions• Equations are non-linear and coupled, therefore, the solution

is obtained by iteration

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Types of FloTHERM Models

Package Level Board Level

Environment

The Procedure for Modeling in FloTHERM

Project Manager

LibraryFloMCAD.BridgeDrawing Board

Solver

FloVIZ

Command Center

Pre-Process

CFD Solver

Post-Process

Optimization

Web PartsFloEDA.Bridge

Creating a FloTHERM Model

• Start FloTHERM• E.g. for windows…

• Start/Programs/MentorMA/FloTHERM 11.3/FloTHERM 11.3 or

• Click on the icon

Creating a FloTHERM Model (Project Manager and Drawing Board window)

Creating a FloTHERM Model (Project Manager window)

The Project Manager is the first window that shows up when FloTHERM is launched. In this window you can access all settings applied to your model, including: Geometry Material and Thermal properties Solver and modeling settings User preferences

The Drawing Board allows you to view and manipulate your geometry, as well as add new geometry via the Geometry Palette that we will see later in this presentation.

Creating a FloTHERM Model (Drawing Board window)

Creating a FloTHERM Model (Visual Editor/Tables Window)

Tables or Visual Editor-Click on either icon to launch

Creating a FloTHERM Model (Profiles Window)

Profiles window-Click on icon to launch

Creating a FloTHERM Model (FloMCADBridge window)

Creating a FloTHERM Model (FloEDABridge window)

Creating a FloTHERM Model (Creating Geometry)

• Geometry can be added using the Geometry Palette located in both the Project Manager and the Drawing Board

Creating a FloTHERM Model (Editing the Model)

• After adding geometry to your model, you will have to define its properties and what it does.

• This is done by adding Attributes– For example:

– What it is made of (material)– How much heat it gives out (thermal)

– There are two ways to do this;– Define your own attributes– Select one from FloTHERM’s preloaded Library

Creating a FloTHERM Model (Editing the Model)

Mouse Operations

Switching mouse modes accomplished by:1. Clicking the various icons in the toolbar2. Using to toggle between Manipulate mode and

SelectF9

Keyboard Shortcuts

[SHIFT]

View from Positive X-Axis

View from Negative X-Axis

View from Positive Y-Axis

View from Negative Y-Axis

View from Positive Z-Axis

View from Negative Z-Axis

Level with Gravity

View selected object(s)

R Refit view

Hide Selection

Reveal Selection[SHIFT]

I[SHIFT] Isometric View

Select “Fix” object first and then select “Move” object.

Creating a FloTHERM Model (Getting Help)

Help Resources…— On-line Help

– Available via the Help button in all FloTHERM windows

— Support– Launches the Mentor Graphics support site,

Supportnet.— Report a Problem On-line

– Brings you directly to a window to submit a Service Request.

— Submit Enhancement Request– Brings you to the Mentor Graphics IDEAS

site.— Mechanical Analysis Community

– Brings you to the Mechanical Analysis window of the Mentor Graphics Communities.

LECTURE 2 BASIC BUILDING BLOCKS AND

INTRODUCTION TO SMARTPARTS

Creating a FloTHERM Model

• Some Definitions:• Primitive - Fundamental geometric entities in FloTHERM• SmartPart - Object parametrically created out of Primitives• Assembly - A group of Primitives, SmartParts and Sub-Assemblies• Attribute - A property that can be attached to Primitives and

SmartParts (e.g. Material)

• The amount of “the world” to include in model is given by the Solution Domain.

• Must include all geometric and thermal / flow features needed to define the model

• Defined using position and size• Right-click on the System Node to access the dialog

Defining the Environment (Solution Domain)

Defining the Environment (Global System Settings)

• The reference values within the Solution Domain are set in the Global System Settings:• Right-click on the System

Node in the Project Manager tree

• Select Global

Solution Domain size – Rules of thumb for forced convection

For forced convection models (e.g. with fans)— Make the domain the same size as

the external chassis— Heat transfer in this model is

dominated by forced convection— Heat loss by natural convection is

minimal from the walls— Heat loss by radiation is also minimal

(no radiation calculations required)

Solution Domain size – Rules of thumb for Natural convection For naturally convected models (no fans

present)— Make the domain bigger than the

chassis— For the space above the chassis,

allow for 2xheight of chassis.— For space below chassis, allow for

1xheight of chassis— Around the sides of the chassis, allow

for 0.5x to 1x width and depth of chassis

— We will also need to turn on Radiation

— Up to 50% of heat transfer is by radiation, the other 50% by natural convection

Min 0.5x

• Certain objects in the Geometry Palette are considered Primitives, and certain objects are considered SmartParts

• SmartParts always have a “Construction” dialog. They are considered smart because they can handle more complex geometries• The Enclosure SmartPart allows you to cut holes into the sides• The Perforated Plate SmartPart allows you to define the venting pattern

• Cuboids and Sources are two examples of Primitives

What Makes a SmartPart Smart?

Cuboid (Primitive)

• Cuboids are the basic building blocks of your FloTHERM model:• A cuboid is used to represent any solid

object in the space (Walls, equipment etc.)• Two modes

• Collapsed (2D) or Non-collapsed (3D)• Modes can be toggled without re-entering

• Sources are used to define thermal boundary conditions in your FloTHERM model:• A source can be located in either solid or

fluid• Available thermal boundary conditions

include• Fixed heat dissipation• Fixed temperature• Linear heat dissipation W.R.T.

temperature• Heat per unit volume• Heat per unit area• Transient heat dissipation

Source (Primitive)

• To model a hollow box, use the Enclosure SmartPart

• The enclosure SmartPart consists of a hollow cuboid shaped box with six solid walls, each of which can be: • Optionally removed• Treated as thick or thin• Holed by one or more resistances or other materials

Enclosure (SmartPart)

Perforated Plate (SmartPart)

• Use the Perforated Plate SmartPart to define vents in your enclosure

• The Perforated Plate performs an automatic calculation of flow resistance based on construction data that you enter:

• Hole size• Hole arrangement • Hole pitch• Free area ratio

Organizing the Model(Project Manager Tree Hierarchy)

• The Project Manager tree is processed from top to bottom

• If objects overlap:• Objects lower in tree take precedence• Exception – Sources always add

• Monitor Points are usually located in critical areas in regards to temperature or air flow

• They allow us to track the solution efficiently, and to quickly determine if our solution is indeed steady state

Keeping Track of the Solution (Monitor Points)

Recommended - Monitor Point Convergence

- IF the temperature monitor points do not vary by more than 0.5 deg C during 30 iterations

AND - IF the Temperature residual is lower than 10

THEN stop the solution

Monitor Point convergence can be used to avoid excessive solution times for those instances where the Termination Residual is too strict.

Tutorial 1-1

Solution domain : 200x200x200 mmMB : 200x1.6x200 mm

FR4 CPU : 25x5x25 mm

Typical QFN15W

Heatsink base : 60x60x5 mmFin number : 15

Fin Height : 25 mmFin Width : 1.2 mmAL 6061

Axial Fan : YSTechYW06025012BS

Ambient : 45 degC

LECTURE 3GRIDDING

Grid lines automatically appear along edges of all objects Object associated If the object is Moved Resized

Keypoints do too!

Keypoint Gridlines

System Grid Tool

System Grid Tool – Maximum Size

Max Size = 25 mm Max Size = 75 mm

System Grid Tool – Minimum Size

Min Size = 0.2 mm Min Size = 2 mm

System Grid Tool – Smoothing

No Smoothing Smoothing Activated

Abrupt Transition

Large Aspect Ratio

System Grid Tool – Gridding Advice

Simple models with a few objects approx. same size – use “Coarse, Med., Fine”

Complicated models with many parts (very big and very small objects) – don’t use

Use manual settings (Max and Min cell size)

Grid Constraints

Grid constraints are used to define grid ON geometry

Sets the Minimum Number of Cells, or Maximum Cell Size within the object

Grid Constraints - Summary

Grid Constraints allow us to specify:— Minimum number of cells across a piece of geometry— Maximum size of cells across a piece of geometry— Minimum size overrules the system grid setting!— Object associated

– Resizing, copying, save/retrieve from the Library Manager

Grid Constraints for Objects

Minimum # 15 Grid Constraint attachedNo Grid Constraints

Grid Constraints - Inflation

Controls grid around an object Two key inputs;

— Inflation Distance— Grid cells in inflation distance

Low and High sides independent

Constraint is Max. Size or Min. Number

Inflation distance defined as Size or percentage of object

Grid Constraint - Inflation

As an example…

– High constraint max. size of 10 mm over 100 mm.

– And the result...

– Low constraint min. of 2 cells for 10% of size

10% of Objects X size

100 mm

High X side

Low X side

Grid Constraints - Inflation

Inflation Distance = 60 mm

Number of cells = 8

Object associated as well Repositioning, resizing, copying and Library saving/retrieving will retain this setting

Using Regions to Define Grid

Grid Constraints can be applied to regions Allows grid to be placed in areas where there are no objects

Using Regions to Define Grid

For example, between two plates

2. Define Region3. Attach Grid

Constraint4. Check Grid

1. Define Geometry

Localized Grid

It allows— Reduction in total number of cells— Reduction in maximum aspect ratio (better grid quality)— Allows more grid cells around areas of importance— Stops very small and fine cells “bleeding” out to rest of the

model— Solution time is reduced

How to Localize Grid ?

Select object, Assembly or Regiona) Use shortcut in PM or DB, or,b) Check Localize option in

“Location” dialog box

Localizing grid steps

1. Select object, Assembly or Region2. Attach Grid Constraint3. Inflate the Grid Constraint4. Localize grid

Localize the Grid ! (with inflated grid constraints)

Unlocalized Localized

BUT what if I don’t inflate the grid ?

Unlocalized Localized

• Without grid inflation:• Solid geometry in contact

with edge of localized grid• Grid due to heat sink fins

“bleeding” out

What if I have many important objects and I want to localize all of them ?

• Use Regions, , as dummy grid objects to place the localized boundary precisely where needed

• Convenient for cluttered geometries that need to be localized

• Graphical indication of the localized boundary is helpful for grid setup

Localized Grid - Positioning

Localized grid spaces can be nested as needed

Can externally or internally abut another localized space

Localized boundary can be completely in solid, fluid, or both.

Cell Aspect Ratios advice

Rules to remember:— Aspect Ratio (L1/L2) of grid cells should be as close to unity as

possible.– 1 is ideal– < 20 good

– >200 convergence trouble is likely

— Transitions from large cells to small cells should be avoided

Avoiding large aspect ratios and small cells

Aspect Ratio Problems:— Minimum Cell Size (System Grid)— Build models with a reasonable tolerance (i.e., build objects to the

nearest mm, inch; depends on the scale of the problem)— Avoiding the creation of small grid cells to begin with decreases

chances of Large Aspect Ratios

Good Grid advice - Heat Sinks

Across a channel:

• 3+ cells for an accurate heat transfer prediction

• 5+ cells for an accurate pressure drop prediction

Across a fin:

• 2+ cells in the solid

Good grid advice – Components and hot objects

For components that are capable of predicting junction and case temperatures (2R, Delphi, or Detailed)

• 6 cells in the 1st millimeter above the component

Note: This is automatically taken care of in FloTHERM v8 when using Auto Grid option in FloEDABridge

Good Grid advice - PCBs

For printed circuit boards

• 3 cells in the 1st millimeter above the board

• 3 cells in the 1st millimeter below the board

Note: This is automatically taken care of in FloTHERM v8 when using the Auto Grid option in FloEDABridge

More generally, this rule is applicable to any surface with a significant amount of heat convecting off it

Steps to get good grid

Set up System grid — Max size 10% of total domain size— Min cell size ≤ smallest object in model— Smoothing

Localized and inflated grid around important objects, or Localized and inflated grid around objects which generate a

lot of cells Keep cell aspect ratio < 200

Simple Example

Smoothing

Localized grid

Minimum 2 cells in thickness of solids

Inflated grid – capturing thermal boundary layer

Grid Independence

Traditional Definition

The point at which the doubling of the number of grid cells causes no change in the solution

Grid Independence

Engineering Definition

The point at which the addition of a large number of grid cells no longer significantly affects the solution.

Significant = 5%, 3% etc

Tutorial 1-2

• System Grid Tool : Solution domain

• Grid Constraints : MB & CPU

• Region : Localized Grid

LECTURE 4 POST-PROCESSING

View Manipulation – Mouse Operations

Switching mouse modes accomplished by:1. Clicking the various icons in the toolbar2. Using to toggle between Manipulate mode and

Select

3. Using to toggle between all three modes.

View Manipulation – Keyboard Shortcuts

[SHIFT]

View from Positive X-Axis

View from Negative X-Axis

View from Positive Y-Axis

View from Negative Y-Axis

View from Positive Z-Axis

View from Negative Z-Axis

Isometric View

Level with Gravity

View selected object(s)

R Refit view

Hide Selection

Hiding/Revealing Geometry

Select Geometry— Graphically in Visual

Editor— Project Manager tree— Visual Editor— Tables

Hide Selection

F12[CTRL] Reveal all hidden objects

View Manipulation – Two Views

Perspective View Orthographic View

Visualizing the Model• Visual Editor window allow views of:

• Results• 3D representation of model

• Model can be represented as:• Solid view• Wireframe view• Switch between views using Mode Palette• Or, use “w” or “s”

wireframe

Surface Plot

• Use selection Mode to select objects in model

• Use manipulator to rotate, zoom, pan model

• Annotate mode allows annotations to be added to picture

• Keyboard shortcut to above modes:

• “F9” to toggle between• Escape key to toggle

between

Selection Mode

Manipulator Mode

to cursor position

Using the Mouse

Assigning Colors to Geometry In the Visual Editor window, you have the ability to override the default

colors assigned to an object. To do so:

Select the object Click on Material->Color in the

lower left pane of the Visual Editor window

Assigning Textures to Geometry The Visual Editor also allows you to assign an image to

the surface of an object. To do so:

Select the object Select one of the preloaded

image files or attach your own

Creating 2D scalar plots(Plane of Temperature)

• In the Visual Editor, you create 2D planes showing the temperature distribution anywhere inside of the Solution Domain.

1. Select the Create Plane icon 2. Go to the Property Sheet in

the bottom left corner, ensure that the Scalar checkbox is checked

3. Select Temperature in the drop down menu

Creating 2D Vector Plots(Plane of Velocity)

• Planes showing Velocity Vectors can be created using the same method as the Temperature plane

• Uncheck the Scalar checkbox• Check the Vector checkbox

• To move the plane to the desired location

• Use left or right cursor keys• OR, use the Manipulator arrow• Make sure that the “Show

Manipulator” option is ticked

Post Processing – Annotations

Annotate Mode

Single click – add Annotation to

1. Geometry

2. Plane Plots

3. Isosurfaces

4. Surface Temperatures

Creating 2D Contour Line Plots

Set in Contour Plane property sheet— Cell Fill (calculated results for

every single cell – no interpolation)

— Interpolated (results are interpolated to give smooth distribution)

— Contour lines

Grid on Contour Plots

Set in Contour Plane property sheet

If model has no results— Use Solve –

Reinitialize in Project Manager

OR, simply press “g” to toggle the grid on or off

Post Processing – Tables

Icons to switch into Tables Mode

The four modes are:

Geometry Only

Tables Only

Tables On Right

Tables Below

Post Processing – Tables• Table types and options are held

under the Tables node.

• Selecting an object row in the Tables window highlights that object in the Project Manager and graphically in the Visual Editor, and vice versa.

• Data sorting is possible with all column headings.

• Data can be directly pushed into your spreadsheet program.

Particle Streamlines Visual Editor allows you to create particle streamlines showing how a

massless particle would move through your product.

To create a particle source:1. Select an object that

will be used as the particles origin

2. Select the Create Particle Source in the Creation Palette at the top of the window.

You also have the ability to view Surface Plots on one or more of the objects in your model.

Surface Plots available include:— Temperature— Computational

Mesh/Grid NOTE: to turn off

the Surface plot, select either the Wireframe or Solid view

Wireframe view, or “w”

Solid view, or “s”

Surface plotSurface Plots

Scalar Fields – changing the temperature scaleWill contain items for all Scalar quantities in the Solution set

Each Scalar will have it’s own property sheet

Saving Viewpoints You can save View Points in the Visual Editor window using the Save

Viewpoint icon located in the palette at the top of the Visual Editor window. You can recall these viewpoints at any time by selecting the desired view in

the list of saved viewpoints on the upper left pane of the Visual Editor window

Saving pictures and movies

To save a screenshot,— Use short cut icon (camera)— OR, Viewer/Output Snapshot in the menu— Can be saved as png, bmp or jpg format

To save a animations of the particles,— Use short cut icon,— Note that this will create an animation of

the particle motion only— It will not animate any Viewpoint animation

Creating particle and viewpoint animations

To create a movie of rotating viewpoints and particle motion, — Use the shortcut icon, — OR Viewer/Output Movie— An *.avi file will be created

The compression codec can also be chosen:— Default is No Compression— There are 4 other formats— Recommend Microsoft Video 1 for

compatibility reasons— The created movie will be able to run

on all Windows PCs (without having to download other codecs)

LECTURE 5 COMMAND CENTER

Lecture Agenda

Basics Introduction Inputs Outputs Solving

Examples of Optimizations

Size and placement of fans and vents Layout of components Heat sink fin count and geometry Fan speeds versus desired component temperature

Scenarios

Base case model has been created and solved Many engineering questions still exist:

— How to improve thermal performance?— How will design operate in different environments?— Is this design the optimal design?

Command Center allows:— Test model in different scenarios— Optimizing model’s thermal design

Where to Start

Load your base case Click the Command Center icon

Command Center Application Window

1. Input Variables

2. Graphical Input

3. Output Variables

4. Scenario Table

5. Solution Monitoring

5 Different Tabs/Windows

Input Variables

Double-click the parameter to vary:— ‘Use as Input

Variable in Scenario’ toggled on

Define the variation method:— Ad Hoc— Linear— Design Parameter— Linear Function

Scenario/Reset can be used to clear all settings in Command Center

Input Variables

Ad Hoc:— Manually specify all variable values— Use the Append button to add a variation

Input Variables (Cont.)

Linear:— Input Variable varied with a specified increment— Enter the Step Size and Number of Steps to define the variants

Design Parameter:— Sets the range of an Input Variable (Minimum and Maximum

values)— A pre-requisite for the automated design tools: Design of

Experiments, Response Surface Optimization, and Sequential Optimization

Linear Function:— Allows linear relationships (y = ax + b) to be defined between

Design Parameters— For use with Design of Experiments, Response Surface

Optimization, and Sequential Optimization

Possible Command Center Variations

Scalars:— Position— Size— Ambient conditions— Gravity orientation— Thermal resistance— SmartPart parameters

– Heat Sink # of fins, fin widths, fin height– Fan volume flow rate

— Grid settings— Power dissipations— And more

Non-Scalar:— Fan failed analysis— Deactivate/Activate

objects– Different fan

models— Swap Library

Attributes– Material (steel to

aluminum)– Surface finish

(polished to anodized)

– Interface materials— Turbulence model— And more

Graphical Input

List shows all existing scenarios— Initially, only the

base case is visible (# 0)

Switch between scenarios by clicking name

Simplified Drawing Board— All shortcut keys— Most Drawing

Board functionality— New geometry

cannot be created

Graphical Input (Cont.)

Check each of the cases Remember to check the

grid for each case by pressing ‘g’ on the keyboard

......

Output Variables

Define the data of interest required from the scenarios

Saves disk space:— Storing full solution is

possible Not limited to Monitor

Points Define cost function

— Required for Response Surface Optimization and Sequential Optimization

Scenario Table

Input Variables— The value for

each scenario (column) can be modified

Solution settings and current status of each scenario

Output Variables— The values will

update as the scenarios solve

Scenario Table (Cont.)

Right-click the settings in the white area to make a change Store Results:

— None— Full— History Only

Initialize From:— All from Base Project— All from No Project— All from Previous Project

Typically use the base case results as the initialized point— Minimize use of disk space

Ready to solve? Hit GO!

• After pressing GO, the Solution Status for each project displays;– Solved– Solving– Queuing

Solution Monitoring

• View the Profiles graphs for each simulation

• Viewable while a solve is active

• Convergence is still important!

Results – Scenario Table

If the full set of data is required, a scenario can be saved as an individual project;— Load into Project

Manager— Required to view results

in Visual Editor Right-click on the scenario

title (top row of the column) and choose Save As

Tutorial 1-3

• Heatsink Base• Fin Number• Fin Width

LECTURE 6 USING MCAD DATA

Agenda

Introduction Simplification Data Conversion Voxelization Additional Functions

Importing CAD files using FloMCAD Bridge

Process: Read in ACIS (.sat), STEP (.stp or .step), IGES (.igs) or STL (.stl)

neutral data format files (parts and assemblies) Alternatively, read in ProE, Solidworks or CATIA files (parts and

assemblies) Simplify MCAD geometry Convert MCAD geometry into FloTHERM entities

Data can also be transferred from FloTHERM to FloMCAD Bridge

Data Import FloMCAD Bridge uses the ACIS solid modelling kernel Incoming data has to be converted to ACIS format This conversion is done by ‘Translator (read) Husks’

FloMCAD.BridgeACIS (SAT)

FloTHERM

Solidworks

1. Simplification

What is the benifit of a thermal simplification?— The reduction of the geometry to an efficient AND accurate

thermal model What constitutes a thermal simplification?

— The removal of thermally insignificant geometry e.g.– Small holes– Small humps– Small chamfers and fillets

Simplification – Where to do it

In your favourite MCAD tool (ProE, Solidworks, CATIA etc) before you export the data— Suppress or delete thermally irrelevant feature like branding logos,

drilling holes, small filets, small chamfers etc.— Suppress irrelevant parts like screws etc.

In FloMCAD using Global and Local Simplification, Replace Tool, Decompose

In FloTHERM after the model was processed in FloMCAD and transferred

Global Simplification

Easy way to quickly perform therm simplifications Works on selected MCAD part or body From [Tools / Global Simplify] or Right click on selected object, then pick [Global Simplify]

Global Simplification – Check the result

Seeing what has just been simplified— Sometimes it is not exactly clear how the geometry has been

simplified— Use CTRL-Z for toggling between ‘before‘ and ‘after‘ simplification

CTRL-Z

Local Simplification

Total control over what is simplified to what extent Targets specific areas for simplification Manually intensive! [Tools / Local Simplify] or Right Click on selected object, pick [Local Simplify] from pop

up menu Hot Keys may be used:

+ Add bounding box- Subtract bound

DEL Removef Flattenl Level

Local Simplification – Example

Feature Simplification— A feature is a collection of faces constituting a geometric pattern— Feature are derived by FloMCAD from the topology of neighbouring

faces— Features can be removed upon selection

Simplification – The Golden Rule

The golden rule of thermal Simplification:

Simplify at least to the extent where the geometry could be created manually in

FloTHERM!

2. Data Conversion

Simple geometry or parts for which a SmartPart exists:[Tools / Single Object]— Replaces a single Part/Body with a FloTHERM Primitive/SmartPart— FloTHERM Primitives: Cuboids, Prisms and Flow Resistances— FloTHERM SmartParts: Fan, PCB, Enclosure, Cylinder and

Perforated Plate Other simple geometry:

[Tools/Decompose]— Automatically simplifies the CAD geometry— Automatically dissectects the CAD geometry— Automatically replaces dissected geometry with ‘Single Objects‘

Dissect already simplified geometry Any other geometry: Voxelize it!

[Tools / Single Object]— Select the MCAD part or body to convert— Pick the [Tools / Single Object] menu or click on the icon the left

tray or right click on the selected object and pick [Single Object] from the pop up menu

— Select the most apropriate FloTHERM entity

Single Objects

FloTHERM Fan SmartPart ready to be transferred to the Project Manager

Single Object Example

Simplifying Grille Work: Arrays of holes or slots can be removed by selecting two oppsing faces then replace with a Perforated Plate

Single Object Remarks

When an MCAD part is replaced with a FloTHERM SmartPart, default parameters are used.

Each SmartPart can be considered as ‘placeholder‘ Each SmartPart has to be reviewed after the transfer to

FloTHERM! Examples:

— Fan: Adjust Hub Diameter, Flow Specifications, Swirl etc.!Hint: In FloTHERM, replace the Fan SmartPart with a fan from the libraries

— PCB: FR4 and Cu are attached; Adjust Cu content!— Perforated Plate: Adjust hole pattern and hole size!

Dissection

Dissection is the process of converting the selected MCAD object into a collection of FloTHERM primitives— The MCAD object is automatically and successively split in to

smaller MCAD bodies— These smaller bodies are constantly analyzed to check whether

they can be replaced with single objects (cuboids, prisms, sloping blocks or cylinders) or further automatic splitting is required

— User can control resolution, butleave the first three setting atdefault (no need to modify if thegeometry was simplified sufficiently)

Dissection – Curved Faces

Arc/Chord Ration is used to determine how an MCAD body with a curved face is split into smaller bodies— The closer A/C is to 1.000 the

better the curve will be resolved

— If the default is too coarse try 1.05 or 1.01

— The closer A/C is to 1.000 the more FloTHERM entities will be used

Decompose

Decompose automatically simplifies and dissects a geometry [Tools / Decompose]

— Select the MCAD part or body to convert. If none is selected the entire geometry will be decomposed (often unwanted).

— Pick the [Tools / Decompose] menu or right click on the selected object and pick [Decompose] from the pop up menu.

— Set an apropriate Simplification Level and Apply. Start with ‘Simple‘ levels.

— Use [Edit / Undo] or CTRL-Z to move back and forth, repeat previous step until right level of simplification is achieved.

Decompose Example

Example: Shield

3. Voxelization – When nothing else works ...

Voxelization is a process that converts MCAD geometry to a collection of (small) cuboids

Use it when the CAD geometry is too complex and [Tool / Single Object], [Tools / Decompose] or Dissect cannot be used

FloMCAD Bridge

Voxelization – always a good idea!

Voxelization - General

Creates a stair stepped representation of the geometry User controls how many cuboids are created Extremely robust

— Always resulting in a FloTHERM representation— Especially when compared to the ‘Dissect‘ process

Voxelization - Inputs

Use [Tools / Voxelize] or click with a part or body selected

Choose either ‘Minimum Number‘ or ‘Maximum Cell Size‘ and enter apropriate values for X,Y and Z directions

An apropriate setting for the Minimum Cell Size will ensure no extremly small cuboids will be created

Collapse Thickness sets thethickness of all collapsed cuboidscreated during the process(when combining 2D faces)

Voxelization – How it works

Overlay grid is specified— Having the bounding box

keypointed— Then having each vertex

keypointed— Then adding additional lines to

satisfy either a minimum number or a maximum size constraint

— If two grid lines are closer together than the minimum cell size one of the lines is removed

For each cell inside the original geometry a cuboid is created

Each cuboid pair that share a full face will be merged into one, repeatedly

Voxelization – Modeling advices

Set the minimum cell size to the smallest dimension that requires representation

Try different values of Minimum Number or Maximum Size until the desired level of resolution is achieved (use CTRL-Z to toggle ‘before‘ and ‘after‘)

Voxelization – Modeling Advices

After transfer into FloTHERM, make sure to inflate and localize the grid on the transferred assembly

Use grid constraints that matches the cell size used

Assign a Material Attribute on the assembly instead of assigning it to individual cuboids

4. Split Body

Useful when parts/bodies are too complex to be processed in one

Split Body Procedure:— Select MCAD body— [Tools / Split Body] or— Right click, pick ‘Split

Body‘ from pop up menu— Select a Face or Vertex— Slice— Split

Align with Axes

Set Selection Mode to ‘Face‘ Rotate Align Part:

— Select the planar face of a part you would like to align to the global cartesian coordinate system

— [Tools / Rotate Align Part] Rotate Align Assembly:

— Select the planar face of a part in the assembly you would like to align

— [Tools / Rotate Align Assembly]

Top & Hide

Parts or bodies can be topped up in the same way as in the Project Manager— Very useful when an assembly containing multiple parts is imported— Parts can be topped up and converted to FloTHERM entities

Parts or bodies can be hidden in the same way as in the Project Manager

Subtract Bodies

Example: Creating a circular hole— In FloTHERM: Create a plate and a

cylinder, radius = 0.5 x hole diameter

— [External / Import Project Geometry]— Select the object from which we

want to subtract the other— CTRL-Select the body to be

subtracted— [Tools / Subtract]— Process resulting body

• After geometry is converted to FloTHERM entities, use [Tools/Transfer Assembly] FloTHERM

• FloMCADBridge and FloTHERM conserves the part name

5. Data Transfer to FloTHERM

Transferred MCAD model in FloTHERM

Remember, transferred parts and assemblies:— Do not have any material properties— Do not have any thermal properties— Do not have any radiation properties

Some parts and assemblies will also need grid constraints Transferred MCAD model will have the same positions as in

original CAD model Part names will also be transferred

Tutorial 2

LECTURE 7USING EDA DATA

Lecture Agenda

Introduction to FloEDABridge

EDA Direct interfaces Processing Components

— Filtering, Component Swapping, Power, Viewing Library Manager Processing the PCB

— Layers, Vias, Stackup Other Capabilities

— Heat sinks, Thermal vias, EM cans, Potting, Daughter boards Transferring to FloTHERM Post Processing Continued

FloEDABridge

intelligently import EDA data into FloTHERM

Use FloEDABridge to create thermal representations of the PCB and IC components for use in FloTHERM

EDA Direct Interfaces

Interfaces and user manuals provided with the FloTHERM installation. Interfaces are available for:— Boardstation: 2005BST or later— Cadence Allegro: 15.7 or later— Zuken CR5000: v9 or v10— Expedition EE2007.8 or later— Cadence APD

Direct Interfaces – Boardstation

EDA interface files are installed into Boardstation Creates a FloTHERM Interface menu Allows the board information to be extracted into a FloEDA file

Direct Interfaces – Allegro & Expedition

Similar process for Cadence Allegro & Expedition All the Settings options are identical to the Board station interface

Direct Interfaces – CR 5000

Uses 3 ASCII output files created by pcout, mrout, and ftout Zuken utilities— pcf (board data)— mrf (manufacturing data)— ftf (footprint data)

Requires license feature ZX0409 Files then converted to FloEDABridge file using supplied command

line utility— ZukenBrdDesToEDAI –job xyz –out xyz.floeda

FloEDABridge Interface

Data Tree

Property Sheet

Library ManagerGraphical View

Viewer Settings Toolbar

Alignment Toolbar

New Geometry Toolbar

Show Library

Viewing the Board Layout Board displayed 2 ways

— Data view— Graphical view

– 2D and 3D

Data view can be shown in 2 different ways— Tree View— Component Table

Component Filtering

Allows filtering of thermally insignificant components Various options

— Side length— Height— Power— Power Density— Reference Designator

Filter results in deactivated component Delete removes component completely

Automatic Component Swapping Tools\Component Library

Swap will replace components with objects saved to the Library.

If package name matches Library name, then package is replaced

— Component will be same location and orientation as original

The user specifies which Library folders should be searched for matches.

Manual Component Swapping

Manual Library Swapping from a right-click pull down

The user specifies which Library item should be swapped in

This applies to most objects you see in FloEDA.Bridge (PCBs, Heat Sinks, stackup, etc.)

Power Maps Apply power

values to multiple components

Simple .csv file— 1st column =

Reference Designator

— 2nd column = Wattage

Can re-import to update

Library Manager Accessed via the Library icon Adding Library components to model

— Select motherboard/daughterboard— Double-click valid Library item

Or— Select component in model— Double-click Library component to “swap”

– Functional groups can also be “swapped”

Or— Select object to receive Library item— Right-click Library item— “load”

Or— Select item in model— Right-click— Replace with Library item …

– Or— Add Library item …

Saving to Library Manager

Use the Library Manager to save items for future models

Select item (motherboard, component, etc)

Right-click “Save To Library …”

— Create new Library folder first by right-clicking (keeps Library organized)

Metallic Layer and Electrical Vias Processing Attach high resolution image of each

metallic layer OR Imported directly with ‘.floeda’ file.

FloEDA file also contains image of through-hole vias. You will need to manually attach this image to the vias in the board tree if a FloEDA files was not utilized.

Images can be processed into a collection of layer patches

— Automatically derived effective thermal conductivities for each patch

Individual resolutions for each layer image

If .floeda file is unavailable— manual attachment of

monochrome image is supported Unprocessed images will have an

orthotropic cuboid created with % Cu calculated from image

Processing Tool

Resolution Slider determines patch size

% Cu bands slider determines the number of orthotropic conductivity material properties created

Click ‘Show’ to see the original image.

Trace layer example, vias processed similarly in same window.

Board Layer Stack up Property window to set placement of trace layers within the depth of the PCB. Option of ‘Equispaced’ which automatically sets the layer spacing.

Guidelines

Conduction cooled applications require high resolution of copper traces— Forced convection in general does not— Warning message appears for more then 500 patches

Power planes, due to their high percentage copper, typically can be left un-processed

Results can be quite dependent on the slider bar settings. Be sure to do a sensitivity analysis when accuracy is paramount

New Geometry in FloEDA Bridge

We can create:— Heatsinks— Thermal and Electrical vias— Cylindrical components (capacitors)— Components (detailed, compact)— Cutouts— Daughter boards— Additional copper layers— Copper patches— EMC cans— Potting compounds

These can be created either in FloEDA Bridge (easier), or in FloTHERM later.

Transfer to FloTHERM

File – Transfer— Transfers motherboard and all children to FloTHERM— !!! Save in FloEDABridge in case of future design updates !!!

– Transfer is a one-way street– Can’t transfer back from FloTHERM into FloEDABridge

Assembly Structure in FloTHERM

Motherboard is placed as last node in Project Manager tree

Tree Structure— Cutouts— Layers— Vias— Top/Bottom Side

– Potting compound, components, Heat Sinks, vias, daughterboard, can

— Regions – Generated for localizing grid

(created by the Auto Gridding feature)

FloTHERM Structure - Notes

Simple components represented with Cuboids Heat Sink represented with SmartPart Patches represented with Hole SmartPart, filled with

generated Material Properties Each component has its own Region created

— Useful for gridding and obtaining numerical results

Tutorial 3

LECTURE 8 RADIATION

Radiation For naturally convected systems,

radiation is important Contributes as much as 50% of

total heat transfer By default, radiation is OFF. To turn it on for the calculations,

go to PM/Model/Modeling 3 options:

— Radiation off (default)— Radiation on— Radiation on – High Accuracy

(additional 2-3% more accurate, but > 3% additional solver time) Not recommended to be used.

2. Preparing Geometry for radiation exchange

We need to attach Radiation Attributes to surfaces that take part in radiation exchange

Create new attributes— Single radiating surfaces, or,— Sub-divided Radiating surfaces

Attach these surfaces to the external surfaces of the selected part

Single radiating surfaces

Remember, For single radiating surface, there is

only ONE value of Thot or Tcold— FloTHERM will calculate the average

surface temperature for the entire surface. Then use this in the radiation equation.

If surface temperatures are uniform, then this is OK.

But if there is a significant temperature difference, then results will not be accurate

Surface T1

Surface T2

T1 > T2

Q = εσA(Thot4 -Tcold

Sub-divided radiating surfaces

Significant temperature difference on a surface – use subdivided radiating surfaces

The selected surface will be subdivided into N number of segments — Note that these segments are different

from the grid cells ! Average surface temperatures are

calculated for each segment Radiation heat exchange equation

repeated N times

Q = fεσA(Thot4 -Tcold

Settings to be used

For single radiating – we only need to enter “Minimum Area Considered”— We can use the default value of 0m2

For sub-divided radiating, we need:— Subdivided Surface tolerance— Minimum Area Considered

Subdivided Surface tolerance is the length of each small segment — e.g. If our surface area = 1m (H) x 1m (W)

we use a surf. Tolerance = 50mm. This means that we get 1000/50 x 1000/50 =

400 segments

Minimum Area Considered

If we have an object with a large surface area, but is very thin (e.g. a PCB)

Side area is very small Negligible radiation from side Therefore we can use “Minimum area

considered” to tolerance out the sides of the PCB— E.g. if PCB is 500x500x1.6mm— To tolerance out the sides, we enter an

area = 801 mm2

PCB thickness = 1.6mm

Side area = 800 mm2

3. Surface finish (Emissivity)

We need to consider the emissivity (ε) of the radiating surfaces

Value varies from 0-1 — 0 means there is no emissivity or radiation— 1 means it is a blackbody

To define emissivity for Smartparts, we do it through the materials attribute:— we assign “Surface Name”— Emissivity value is specified— NOTE that if Library Manager materials are

used, then a default ε value is given

For primitives like cuboids, prisms etc.— We can also use the Surface Attribute to define

ε,— Or, we can use Material/Surface Name

Radiation Model and limitations

The Gray Body radiation model is used in FloTHERM— This is a better approximation of everyday objects used

Surface to surface radiation considered. Increase in fluid temperature due to radiation will not be considered.

FloTHERM will determine the View Factor or Exchange Factor (efg.exe) automatically

If there are too many radiation surfaces or segments, then the Exchange Factor calculation will take much longer (also use up a lot of RAM)

Efg.exe may crash if you have millions of segments and you run out of RAM !

Each iteration will take much longer to complete

LECTURE 9 TROUBLESHOOTING

Residual Profiles and definitions

R esidualE rror

Ite ration

ResidualError

Iteration

Convergence

Divergence

Stable

ResidualError

Iteration

ResidualError

Iteration

Oscillating

Why doesn’t my model converge ? (Steady state models)

Common reasons: — Errors made during set up— Grid not adequately refined— Inappropriate Termination Criteria— Control Parameters not suitably set— Natural Instability

First step - Sanity Check

Checks the model for potential errors in the problem setup

Can be run independently of the solver

Avoid wasting time on ill-posed problems!

Sanity Check (Cont.)

• Problems reported in Message Window

• Errors: Model can not be run• Warnings: Something might be wrong with the model• Informationals: Items of interest. Not usually indicative

of a problem

Sanity Check Example

• Warning - Object has been entirely overwritten• Cause: hierarchy rule not followed

2nd Step – Check for Model Input Errors

Input Errors during set up; — Unrealistic values

– Entering 5 MW instead of 5 mW— Unrealistic geometry

– Eg: Placing a fan so half of it is inside a wall— Problem is ill-posed

– Sealed system with no material for the enclosure

3rd step: Check the Grid

• There needs to be sufficient grid to capture all of the relevant physics:

• Add grid where you suspect the largest temperature and velocity gradients will be present;

• Heat sources• Heat sinks• Fans• Inlet/Outlets vents

• The Field Error tool is a great way to identify where more grid should be added

Smoothing

Localized grid

Minimum 2 cells in thickness of solids

Min 2 cells in hot solids, Min 3 cells in narrow channels

Min 6 cells in 1st mm above hot objects/chips, Min 3 cells in 1st mm above & below PCB

Error Field Tool

Activate Error Field Storage; — Set in Solver Control

Error Field Storage saves the error in each Grid Cell;— Visual Editor to locate

maximum/minimum error— Display the grid

– Error field uncovers poor grid

Error located in unimportant area;— Monitor Points reached steady state

– No need to force convergence

4th step: Check Termination Criteria

Examples;— System with multiple fluids (i.e. air and water)

– Termination criteria is based on air density — System with ducts and fans

– Termination criteria based on maximum fan velocity

5th Step: False Time Steps

Set under Solver Control The values for x, y, z velocities and Temperature can be

changed (User Specified) False time steps are used to control the convergence What and how much to change depends on the convergence

graphs

Converging Profile

This is exactly what you want to see in your residual plot

No user action is recommended

R esidualE rror

Iteration

Diverging Profile

— STOP the solution immediately— Check the obvious first

– Examine;– Sanity Check– User Inputs– Modeling Decisions– Grid Inadequacies

— Locate the Problem Spot(s):– Monitor Points and Error Field – Deactivate Objects/Assemblies to isolate problem

— Results will be extremely incorrect — If model and grid are OK, reduce automatic

False Time Step value by 10x first.— Re-initialize before solving a diverging

ResidualError

Iteration

Stable Profile

Check user inputs— Common error is neglecting to assign

materials and thus trapping heat– Heat that cannot escape is permanent

residual error!

Check gridding with Field Error Check Termination Criteria

— Try increasing False Time step values (start with x2 automatic value)

If model and grid are OK,— Use Monitor Point plots and

engineering judgment to determine quality of results

— Activate Monitor Point Convergence for Temperature

ResidualError

Iteration

Oscillating Profile

Check Gridding with Field Error Adjust Solution Controls:

— Reduce False Time Step for oscillating variable

— start with 2x reduction of automatic false time steps

Use Monitor Point plots and engineering judgment to determine quality of results

Maybe flow behaviour is naturally unstable (e.g. thermal plume above naturally convected hot object).

May require transient analysis to solve model

ResidualError

Iteration

Best Practice Techniques

Before solving a model:— Sanity Check— Use Monitor Points to track variables at points of interest — Grid carefully with attention to expected areas of large gradients

After solving a model:— System mass flow and energy balance— Error Field to locate maximum error – check the grid

LECTURE 10MANAGING PROJECTS

• Before building, save your project:1. In the Project Manager, click

on: [Project / Save]2. Enter project name3. Choose Solution Directory4. Add Notes

– Allows description to be added to a project

– Could be used to track changes

– Can be displayed from [Project / Load] dialog

Managing Projects (Saving Projects)

Managing Projects (Loading Projects)

• To load an already solved project:1. In the Project Manager click on:

[Project / Load]2. In the upper left window select a

project to load3. Click Load

• If the project of interest is not visible in the upper left window verify that the correct Project Solution Directory is selected.• To select a different Project

Solution Directory select [Browse...] and navigate to an alternative directory

Managing Projects(Importing and Exporting Projects)

Import / Export an entire project via a right-click on the top node in the Project Manager tree

Formats to import:– FloXML– PDML– V1.4 files– V2/V3 *.project– Pack Files

Formats to export:– IGES– PDML– Pack Files– Pack Files (no results)– SAT

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