FloTHERM Basic
Training
Jay Chien
易富迪科技 / EFD Corporation
http://www.efd.com.tw
LECTURE 1
INTRODUCTION TO FloTHERM
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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
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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 computerbased simulation”
Versteeg & Malalasekera, “An Introduction to Computational Fluid
Dynamics: The Finite Volume Method”
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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…
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FloTHERM – What Does it do?

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
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FloTHERM – What Does it do?
1.
Conduction through a solid or a stationary fluid
Q = kA(ΔT/Δx)
T1 > T2
T1
T2
Heat Flow
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FloTHERM – What Does it do?
2.
Convection from a surface to a moving fluid
Moving Fluid T2
Q = hAΔT
T1 > T2
Heat Flow
Surface T1
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FloTHERM – What Does it do?
3.
Radiation heat exchange between two surfaces
Q = εσA(Thot4 -Tcold4)
T1 > T2
Surface T1
Surface T2
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FloTHERM – What Does it do?
•
FloTHERM divides both the solid and fluid spaces into many
small grid cells and solves conservation equations within
each cell.
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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
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How Does FloTHERM Work?
•
The Navier-Stokes Equations can be expressed in a common
form
•
Partial differential equations, therefore can not be solved in
“raw” form




   div  V    grad   S 
t
transient + convection – diffusion = Source
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How Does FloTHERM Work?
•
Need to use the Finite Volume Approach
•
Taylor series expansions
•
Equations are non-linear and coupled, therefore, the solution
is obtained by iteration
h
z
lx
hy
P
aPP  ahxhx  alxlx  ahyhy  alyly  ahzhz  alzlz  altlt  SP
lt
ly
hx
lz
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Types of FloTHERM Models
Package Level
Board Level
Environment
Rack
Level
Level
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The Procedure for Modeling in FloTHERM
Project Manager
Pre-Process
Drawing Board
FloMCAD.Bridge
FloEDA.Bridge
CFD Solver
Solver
Post-Process
FloVIZ
Optimization
Command Center
Library
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Web Parts
Creating a FloTHERM Model
•
Start FloTHERM
• E.g. for windows…
•
Start/Programs/MentorMA/FloTHERM 11.3/FloTHERM 11.3
or
•
Click on the icon
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Creating a FloTHERM Model
(Project Manager and Drawing Board window)
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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
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Creating a FloTHERM Model
(Drawing Board window)
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.
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Creating a FloTHERM Model
(Visual Editor/Tables Window)
Tables or
Visual
EditorClick on
either
icon to
launch
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Creating a FloTHERM Model
(Profiles Window)
Profiles
windowClick on
icon to
launch
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Creating a FloTHERM Model
(FloMCADBridge window)
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Creating a FloTHERM Model
(FloEDABridge window)
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Creating a FloTHERM Model
(Creating Geometry)
• Geometry can be added using the Geometry Palette located in both the
Project Manager and the Drawing Board
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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
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Creating a FloTHERM Model
(Editing the Model)
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Mouse Operations
Switching mouse modes accomplished by:
1. Clicking the various icons in the toolbar
2. Using
Select
F9
to toggle between Manipulate mode and
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Keyboard Shortcuts
[SHIFT]
[SHIFT]
[SHIFT]
[SHIFT]
I
Isometric View
View from Negative X-Axis
L
Level with Gravity
Y
View from Positive Y-Axis
V
View selected object(s)
Y
View from Negative Y-Axis
R
Refit view
Z
View from Positive Z-Axis
F12
X
View from Positive X-Axis
X
Z
View from Negative Z-Axis
[SHIFT] F12
Hide Selection
Reveal Selection
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Align
Select “Fix” object first and then select
“Move” object.
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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.
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LECTURE 2
BASIC BUILDING BLOCKS AND
INTRODUCTION TO
SMARTPARTS
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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)
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Defining the Environment (Solution Domain)
•
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
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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
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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)
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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
2y
Min 0.5x
y
x
y
0.5z
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z
What Makes a SmartPart Smart?
•
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
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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
data
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Source (Primitive)
• 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
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Enclosure (SmartPart)
•
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
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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
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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
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Keeping Track of the Solution (Monitor Points)
• 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
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Keeping Track of the Solution (Monitor Points)
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Recommended - Monitor Point Convergence
Monitor Point convergence can be used to avoid excessive solution
times for those instances where the Termination Residual is too strict.
- 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
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Tutorial 1-1
Solution domain :
200x200x200 mm
MB : 200x1.6x200 mm
FR4
CPU : 25x5x25 mm
Typical QFN
15W
Heatsink base : 60x60x5 mm
Fin number : 15
Fin Height : 25 mm
Fin Width : 1.2 mm
AL 6061
Axial Fan : YSTech
YW06025012BS
Ambient : 45 degC
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LECTURE 3
GRIDDING
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Keypoint Gridlines
 Grid lines automatically
appear along edges of all
objects
 Object associated
 If the object is
 Moved
 Resized
 Keypoints do too!
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System Grid Tool
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System Grid Tool – Maximum Size
Max Size = 25 mm
Max Size = 75 mm
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System Grid Tool – Minimum Size
Min Size = 0.2 mm
Min Size = 2 mm
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System Grid Tool – Smoothing
Large Aspect Ratio
Abrupt
Transition
No Smoothing
Smoothing Activated
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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)
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Grid Constraints

Grid constraints are used to define
grid ON geometry

Sets the Minimum Number of Cells, or
Maximum Cell Size within the object
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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
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Grid Constraints for Objects
No Grid Constraints
Minimum # 15 Grid Constraint attached
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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
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Grid Constraint - Inflation

As an example…
100 mm
High X side
Low X side
– Low constraint min. of 2
cells for 10% of size
– High constraint max. size
of 10 mm over 100 mm.
– And the result...
10% of Objects X size
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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
60 mm
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Using Regions to Define Grid
Grid Constraints can be applied to regions
 Allows grid to be placed in areas where there are no objects

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Using Regions to Define Grid

For example, between two plates
1. Define Geometry
2. Define Region
3. Attach Grid
Constraint
4. Check Grid
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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
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How to Localize Grid ?

Select object, Assembly or Region
a)
Use shortcut in PM or DB, or,
b)
Check Localize option in
“Location” dialog box
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Localizing grid steps
1.
Select object, Assembly or Region
2.
Attach Grid Constraint
3.
Inflate the Grid Constraint
4.
Localize grid
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Localize the Grid ! (with inflated grid
constraints)
Unlocalized
Localized
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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
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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
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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.
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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
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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
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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
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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
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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
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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
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Simple Example
Minimum 2 cells in
thickness of solids
Localized grid
Smoothing
Inflated grid – capturing
thermal boundary layer
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Grid Independence
Traditional
Definition
The point at which
the doubling of the
number of grid
cells causes no
change in the
solution
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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
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Tutorial 1-2
• System Grid Tool :
Solution domain
• Grid Constraints :
MB & CPU
• Region :
Localized Grid
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LECTURE 4
POST-PROCESSING
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View Manipulation – Mouse Operations
Switching mouse modes accomplished by:
1. Clicking the various icons in the toolbar
2. Using
Select
3. Using
F9
ESC
to toggle between Manipulate mode and
to toggle between all three modes.
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View Manipulation – Keyboard Shortcuts
[SHIFT]
[SHIFT]
[SHIFT]
X
View from Positive X-Axis
I
Isometric View
X
View from Negative X-Axis
L
Level with Gravity
Y
View from Positive Y-Axis
V
View selected object(s)
Y
View from Negative Y-Axis
R
Refit view
Z
View from Positive Z-Axis
F12
Z
View from Negative Z-Axis
[SHIFT] F12
Hide Selection
Reveal Selection
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Hiding/Revealing Geometry

Select Geometry
— Graphically in Visual
Editor
— Project Manager tree
— Visual Editor
— Tables
F12
[SHIFT] F12
[CTRL] F12
Hide Selection
Reveal Selection
Reveal all hidden objects
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View Manipulation – Two Views
Perspective View
Orthographic View
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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”
Solid
wireframe
Surface Plot
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Using the Mouse
Selection
Mode
Manipulator
Mode
to cursor
position
•
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
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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
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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
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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
1
2
3
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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
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Post Processing – Annotations
Annotate Mode
Single click – add Annotation
to
1. Geometry
2. Plane Plots
3. Isosurfaces
4. Surface Temperatures
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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
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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
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Post Processing – Tables
Icons to switch into Tables Mode
The four modes are:
Geometry Only
Tables Only
Tables On
Right
Tables Below
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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.
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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.
2
1
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Solid view, or
“s”
Surface Plots

You also have the
ability to view
Surface Plots on
one or more of
the objects in
your model.

Surface Plots
available include:
Wireframe
view, or “w”
Surface plot
— Temperature
— Computational
Mesh/Grid

96
NOTE: to turn off
the Surface plot,
select either the
Wireframe or
Solid view
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Scalar Fields – changing the temperature scale
Will contain items for all Scalar
quantities in the Solution set
Each Scalar will have it’s own
property sheet
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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
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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
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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)
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LECTURE 5
COMMAND CENTER
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Lecture Agenda

Basics Introduction

Inputs

Outputs

Solving
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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
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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
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Where to Start

Load your base case

Click the Command Center icon
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Command Center Application Window
5 Different Tabs/Windows
1. Input Variables
2. Graphical Input
3. Output Variables
4. Scenario Table
5. Solution Monitoring
.....
106
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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
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Input Variables

Ad Hoc:
— Manually specify all variable values
— Use the Append button to add a variation
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Input Variables (Cont.)

Linear:
— Input Variable varied with a specified increment
— Enter the Step Size and Number of Steps to define the variants
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Input Variables (Cont.)

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
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Input Variables (Cont.)

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
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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
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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
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Graphical Input (Cont.)
......
114

Check each of the cases

Remember to check the
grid for each case by
pressing ‘g’ on the
keyboard
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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
.
115
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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
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Scenario Table (Cont.)
Right-click the settings in the white area to make a change
 Store Results:

— None
— Full
— History Only

Initialize From:

Typically use the base case results as the initialized point
— All from Base Project
— All from No Project
— All from Previous Project
— Minimize use of disk space
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Scenario Table (Cont.)
 Ready
to solve?
 Hit GO!
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Scenario Table (Cont.)
• After pressing GO, the
Solution Status for
each project displays;
– Solved
– Solving
– Queuing
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Solution Monitoring
• View the Profiles graphs for
each simulation
• Viewable while a solve is
active
• Convergence is still
important!
....
120
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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
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Tutorial 1-3
• Heatsink Base
• Fin Number
• Fin Width
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LECTURE 6
USING MCAD DATA
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Agenda

Introduction

Simplification

Data Conversion

Voxelization

Additional Functions
124
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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
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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’
STEP
IGES
FloMCAD.Bridge
ACIS (SAT)
FloTHERM
SAT
STL
ProE
Catia
Solidworks
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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
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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
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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]
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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
CTRL-Z
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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:
+
DEL
f
l
Add bounding box
Subtract bound
Remove
Flatten
Level
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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
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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!
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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!
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Single Objects

[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
FloTHERM Fan
SmartPart ready to
be transferred to the
Project Manager
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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
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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!
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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, but
leave the first three setting at
default (no need to modify if the
geometry was simplified sufficiently)
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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
A
C
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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.
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Decompose Example

Example: Shield
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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
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Voxelization – always a good idea!
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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
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Voxelization - Inputs

Use [Tools / Voxelize] or click
selected
with a part or body

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 the
thickness of all collapsed cuboids
created during the process
(when combining 2D faces)
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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,
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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‘)
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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
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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
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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]
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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
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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
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5. Data Transfer to FloTHERM
•
After geometry is converted
to FloTHERM entities, use
[Tools/Transfer Assembly]
FloTHERM
•
FloMCADBridge and FloTHERM
conserves the part name
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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
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Tutorial 2
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LECTURE 7
USING EDA DATA
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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
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FloEDABridge

FloEDABridge
intelligently import
EDA data into
FloTHERM

Use FloEDABridge to
create thermal
representations of the
PCB and IC
components for use in
FloTHERM
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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
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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
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Direct Interfaces – Allegro & Expedition

Similar process for Cadence Allegro & Expedition

All the Settings options are identical to the Board station interface
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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
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FloEDABridge Interface
Alignment Toolbar
Graphical View
Library Manager
New
Geometry
Toolbar
Show
Library
Viewer
Settings
Toolbar
Data Tree
Property
Sheet
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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
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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
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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.
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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.)
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Power Maps

Apply power
values to multiple
components

Simple .csv file
— 1st column =
Reference
Designator
— 2nd column =
Wattage

Can re-import to
update
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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
Or
— Select object to receive Library item
— Right-click Library item
— “load”
— Select item in model
— Right-click
— Replace with Library item …
– Or
— Add Library item …
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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 rightclicking (keeps Library
organized)
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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
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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.
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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.

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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
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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.
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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
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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)
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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
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Tutorial 3
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LECTURE 8
RADIATION
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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.
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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
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Single radiating surfaces


Remember,
For single radiating surface, there is
only ONE value of Thot or Tcold
Q = εσA(Thot4 -Tcold4)
— 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
T1 >
T2
Surface
T1
Surface
T2
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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
50mm
Q = fεσA(Thot4 -Tcold4)
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1m
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

50mm
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
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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
PCB thickness = 1.6mm
500mm
Side area =
800 mm2
— E.g. if PCB is 500x500x1.6mm
— To tolerance out the sides, we enter an
area = 801 mm2
500mm
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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
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Radiation Model and limitations

The Gray Body radiation model is used in FloTHERM

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




— This is a better approximation of everyday objects used
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LECTURE 9
TROUBLESHOOTING
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Residual Profiles and definitions
Stable
Convergence
Residual
Error
R e sid u a l
E rro r
Ite ra tio n
Iteration
Oscillating
Divergence
Residual
Error
Residual
Error
Iteration
Iteration
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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
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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 illposed problems!
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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
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Sanity Check Example
• Warning - Object has been entirely overwritten
• Cause: hierarchy rule not followed
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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
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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
Min 6 cells in 1st mm above hot
objects/chips, Min 3 cells in 1st mm
above & below PCB
Min 2 cells in hot solids, Min 3
cells in narrow channels
Minimum 2 cells in
thickness of solids
Localized grid
Smoothing
• The Field Error tool is a great way to identify where more grid
should be added
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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
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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
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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
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Converging Profile

This is exactly what you want to
see in your residual plot

No user action is recommended
R e sid u a l
E rro r
Ite ra tio n
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Diverging Profile
— STOP the solution immediately
— Check the obvious first
–
Examine;
– Sanity Check
– User Inputs
– Modeling Decisions
– Grid Inadequacies
Residual
Error
— Locate the Problem Spot(s):
–
–
Iteration
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
model
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Stable Profile

Check user inputs
— Common error is neglecting to assign
materials and thus trapping heat
– Heat that cannot escape is permanent
residual error!
Residual
Error
Check gridding with Field Error
 Check Termination Criteria

Iteration
— 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
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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
Residual
Error
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

Iteration
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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
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LECTURE 10
MANAGING PROJECTS
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Managing Projects (Saving Projects)
•
Before building, save your
project:
1. In the Project Manager, click
on: [Project / Save]
2. Enter project name
3. Choose Solution Directory
4. Add Notes
– Allows description to be
added to a project
– Could be used to track
changes
– Can be displayed from
[Project / Load] dialog
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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 load
3. 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
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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:
–
–
–
–
–

208
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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