CST Studio Suite

CST Studio Suite
Thermal and Mechanical Simulation
3DS.COM/SIMULIA | © Dassault Systèmes | CST Studio Suite

Workflow &
Solver Overview
Version 2020.0 - 8/16/2019

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| CST
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2
Table of contents
Chapter 1 – Introduction.......................................................................................................................... 5
Welcome ............................................................................................................................................. 5
How to Get Started Quickly ............................................................................................................. 5
What is CST MPhysics Studio? ...................................................................................................... 5
Who Uses CST MPhysics Studio? .................................................................................................. 5
CST MPhysics Studio Key Features ................................................................................................... 6
General ............................................................................................................................................ 6
Structure Modeling .......................................................................................................................... 6
Mechanics Solver ............................................................................................................................ 6
Thermal Steady State Solver .......................................................................................................... 6
Thermal Transient Solver ................................................................................................................ 7
Conjugate Heat Transfer Solver...................................................................................................... 7
SAM (System and Assembly Modeling) .......................................................................................... 7
Visualization and Secondary Result Calculation............................................................................. 8

Result Export ................................................................................................................................... 8
Automation ...................................................................................................................................... 8
About This Manual .............................................................................................................................. 9
Document Conventions ....................................................................................................................... 9
Your Feedback ................................................................................................................................ 9
Chapter 2 – Simulation Workflows ........................................................................................................ 10
Simulation Workflow: Structural Mechanics ...................................................................................... 10
The Structure................................................................................................................................. 10
Create a New Project .................................................................................................................... 10
Open the QuickStart Guide ........................................................................................................... 11
Define the Units ............................................................................................................................. 11
Model the Structure ....................................................................................................................... 12
Traction and Displacement Boundaries ........................................................................................ 18
Mesh Settings................................................................................................................................ 20
Start the Simulation ....................................................................................................................... 20
Analyze the Solution of the Tetrahedral Solver............................................................................. 21
Summary ....................................................................................................................................... 24
Simulation Workflow: Coupled EM-CHT Simulation ......................................................................... 24
EM-Thermal Link Set-up ............................................................................................................... 25
Loss Import.................................................................................................................................... 26
Background and Boundary Conditions ......................................................................................... 27
Mesh Settings................................................................................................................................ 30
Solver Parameters ........................................................................................................................ 31
Coupled Run ................................................................................................................................. 33
Simulation Results ........................................................................................................................ 33
Chapter 3 – Solver Overview ................................................................................................................ 36
3
Solvers and Sources ......................................................................................................................... 36
Mechanical Solver ............................................................................................................................. 36
Thermal and Conjugate Heat Transfer Solvers ................................................................................ 36
Background Material ..................................................................................................................... 36
Material Properties ........................................................................................................................ 38
Boundary Conditions ..................................................................................................................... 40
Sources and Loads ....................................................................................................................... 42
Monitors at Points ......................................................................................................................... 48
Monitors on Faces ......................................................................................................................... 49
3D Field Monitors .......................................................................................................................... 50
Steady State Thermal Solver Parameters .................................................................................... 51
Excitation Signal Settings .............................................................................................................. 52
Transient Thermal Solver Settings ................................................................................................ 52
Result Types ................................................................................................................................. 54
Chapter 4 – Finding Further Information ............................................................................................... 57
The Quick Start Guide ....................................................................................................................... 57

Online Documentation....................................................................................................................... 57
Tutorials and Examples..................................................................................................................... 58
Technical Support ............................................................................................................................. 58
Macro Language Documentation ...................................................................................................... 58
History of Changes ............................................................................................................................ 58
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Chapter 1 – Introduction
Welcome
Welcome to CST Studio Suite®, the powerful and easy-to-use electromagnetic field simulation
software. This program combines a user-friendly interface with unsurpassed simulation
performance. CST Studio Suite contains a variety of solvers for carrying out Thermal and
Mechanical Simulation. They are all grouped as a specific Thermal and Mechanical Module, also
known as CST MPhysics® Studio.
Please refer to the CST Studio Suite - Getting Started manual first. The following explanations
assume that you have already installed the software and familiarized yourself with the basic
concepts of the user interface.
How to Get Started Quickly

We recommend that you proceed as follows:
1. Read the CST Studio Suite - Getting Started manual.

2. Work through this document carefully. It provides all the basic information necessary to
understand the advanced documentation.
3. Look at the examples provided in the Component Library (File: Component Library 
Examples). Especially the examples which are tagged as Tutorial provide detailed

information of a specific simulation workflow. Press the Help button of the individual
component to get to the help page of this component. Please note that all these examples
are designed to give you a basic insight into a particular application domain. Real-world
applications are typically much more complex and harder to understand if you are not
familiar with the basic concepts.
4. Start with your own first example. Choose a reasonably simple example which will allow
you to quickly become familiar with the software.
5. After you have worked through your first example, contact technical support for hints on
possible improvements to achieve even more efficient usage of the software.
What is CST MPhysics Studio?

CST MPhysics Studio is a software package from the CST Studio Suite family which allows
thermal and mechanical simulations. It simplifies the process of defining the structure by providing
a powerful solid modeling front end, which is based on the ACIS modeling kernel. Strong graphic
feedback simplifies the definition of your device even further. After the component has been
modeled, a fully automatic meshing procedure is applied before a simulation engine is started.
A key feature of CST MPhysics Studio is its tight integration with the other CST Studio products.
This allows an easy to use workflow for coupled EM-Multiphysics simulations.
A further outstanding feature is the full parameterization of the structure modeler, which enables
the use of variables in the definition of your component. In combination with the built-in optimizer
and parameter sweep tools, CST MPhysics Studio is capable of analyzing and designing thermal
and mechanical aspects of devices.
Who Uses CST MPhysics Studio?

Anyone who needs to investigate thermal and mechanical aspects of electromagnetic devices.
Of course it is also possible to use the product standalone, but the full set of capabilities deploys
when coupling the thermal and mechanical simulators with other products from the CST Studio
Suite family such as CST Microwave Studio®, CST Design Studio™, CST EM Studio® or CST
Particle Studio®.
5
CST MPhysics Studio Key Features
The following list gives you an overview of the CST MPhysics Studio main features. Note that not
all of these features may be available to you because of license restrictions. Contact a sales
office for more information.
General
 Native graphical user interface based on Windows 7 (SP 1 or later), Windows 2008
Server R2 (SP 1 or later), Windows 8.1, Windows 2012 Server R2, Windows 10 and
Windows Server 2016
 The structure can be viewed either as a 3D model or as a schematic. The latter allows
for easy coupling of thermal simulation parameters with circuit simulation.
 Various independent types of solver strategies (based on hexahedral as well as
tetrahedral meshes) allow accurate simulations with a high level of performance for a
wide range of multi-physical applications.
 For specific solvers highly advanced numerical techniques offer features like Perfect
Boundary Approximation® (PBA) for hexahedral grids and curved and higher order
elements for tetrahedral meshes.
Structure Modeling
 Advanced ACIS-based, parametric solid modeling front end with excellent structure
visualization

 Feature-based hybrid modeler allows quick structural changes
 Import of 3D CAD data from ACIS® SAT/SAB, CATIA®, SOLIDWORKS®, Autodesk
Inventor, IGES, VDA-FS, STEP, PTC Creo, Siemens NX, Parasolid, Solid Edge,
CoventorWare, Mecadtron, NASTRAN, STL or OBJ files
 Import of 2D CAD data by DXF, GDSII and Gerber RS274X, RS274D files
 Import of EDA data from design flows including Cadence Allegro® / APD® / SiP®, Mentor
Graphics Expedition®, Mentor Graphics PADS®, Mentor Graphics HyperLynx®, Zuken
CR-5000® / CR-8000®, IPC-2581 and ODB++® (e.g. Altium Designer, Mentor Graphics
Boardstation®, CADSTAR®, Visula®)
 Import of PCB designs originating from CST PCB Studio®
 Import of 2D and 3D sub models
 Import of Agilent ADS® layouts
 Import of Sonnet® EM models
 Import of a visible human model dataset or other voxel datasets
 Export of CAD data to ACIS SAT/SAB, IGES, STEP, NASTRAN, STL, DXF, GDSII,
Gerber or POV files
 Parameterization for imported CAD files
 Material database
 Structure templates for simplified problem setup
Mechanics Solver
 Temperature dependent Young’s modulus
 Displacement boundary condition
 Traction boundary condition
 Thermal expansion
 Neo-Hookean material model for simulation of large deformations
 Various stress plots: von Mises, hydrostatic and tensor components
 Strain plots including visualization of the volumetric strain
 Nonlinear solver computes the Green-Lagrange and the Almansi-strain as well as the
2nd Piola-Kirchhoff and Cauchy stress tensors
 Displacement plot including visualization of deformed mesh
 Import of force densities from EM-solvers
 Export of deformed structure to CST Microwave Studio
Thermal Steady State Solver

 Isotropic and anisotropic material properties
 Bioheat material properties
 Nonlinear material properties (Bioheat properties and thermal conductivity)
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 Thermal contact resistance
 Moving media
 Convection for human voxel models
 Heat transfer by conduction in volumes
 Heat transfer by convection and radiation through surfaces
 Sources: fixed and floating temperatures, heat sources, eddy current and stationary
current loss fields, volume/surface power loss distributions in dielectric or lossy metal
materials imported from CST Microwave Studio, CST EM Studio or CST PCB Studio,
crashed particle loss distribution from CST Particle Studio
 Adiabatic / fixed or floating temperature / open boundary conditions
 Automatic parameter studies using built-in parameter sweep tool
 Automatic structure optimization for arbitrary goals using built-in optimizer
 Network distributed computing for optimizations, parameter sweeps and remote
calculations
 Thermal conductance matrix calculation
 Equivalent Circuit EMS/MPS/DS Co-Simulation for linear problems
Thermal Transient Solver

 Isotropic and anisotropic material properties
 Bioheat material properties
 Nonlinear material properties (Bioheat properties, thermal conductivity and heat
capacity)

 Thermal contact resistance
 Moving media
 Convection for human voxel models
 Heat transfer by conduction in volumes
 Heat transfer by convection and radiation through surfaces
 Sources: fixed, initial and floating temperatures, heat sources, eddy current and
stationary current loss fields, volume/surface power loss distributions in dielectric or lossy
metal materials imported from CST Microwave Studio, CST EM Studio or CST PCB
Studio, crashed particle loss distribution from CST Particle Studio
 Adiabatic / fixed or floating temperature / open boundary conditions
 Low or high order time integration method, constant or adaptive time step width
 Network distributed computing for remote calculations
 Calculation of CEM43°C thermal dose in biological tissues
Conjugate Heat Transfer Solver

 Steady-state solver for incompressible laminar or turbulent flows
 Conjugate heat transfer between solids and fluids
 Boussinesq approximation for buoyancy force in flows
 Surface-to-surface radiation with automatic calculation of view factors
 Opening: velocity- and pressure-based inlets and outlets
 Walls: slip/no slip, isothermal and adiabatic
 Internal heat sources
 External heat sources imported from CST Microwave Studio or CST EM Studio
 Axial fan model support
 Planar and volume flow resistance model support
 Two-resistor component model support
 Thermal contact properties: resistance
 Thermal surface properties: surface emissivity and heat transfer coefficient
 Full GPU acceleration support
SAM (System and Assembly Modeling)

 3D representations for individual components
 Automatic project creation by assembling the schematic’s elements into a full 3D
representation
 Manage project variations derived from one common 3D geometry setup
 Coupled Multiphysics simulations by using different combinations of coupled
circuit/EM/Thermal/Stress projects
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Visualization and Secondary Result Calculation
 Online visualization of intermediate 1D results during simulation
 Import and visualization of external xy-data
 Copy / paste of xy-datasets
 Fast access to parametric data via interactive tuning sliders
 Automatic saving of parametric 1D results
 Multiple 1D result view support
 Various 2D and 3D field visualization options for thermal fields, heat flow densities,
displacement fields, stress fields, etc.
 Animation of field distributions
 Display and integration of 2D and 3D fields along arbitrary curves

 Integration of 3D fields across arbitrary faces
 Hierarchical result templates for automated extraction and visualization of arbitrary

results from various simulation runs. These data can also be used for the definition of
optimization goals.
Result Export
 Export of result data such as fields, curves, etc. as ASCII files
 Export screen shots of result field plots

Automation
 Powerful VBA (Visual Basic for Applications) compatible macro language with editor and
macro debugger
 OLE automation for seamless integration into the Windows environment (Microsoft
Office®, MATLAB®, AutoCAD®, MathCAD®, Windows Scripting Host, etc.)
8
About This Manual
This manual is primarily designed to enable a quick start of CST MPhysics Studio. It is not
intended to be a complete reference guide to all the available features but will give you an
overview of key concepts. Understanding these concepts will allow you to learn how to use the
software efficiently with the help of the online documentation.
Document Conventions
 Buttons that should be pressed within dialog boxes are always written in italics, e.g. OK.
 Key combinations are always joined with a plus (+) sign. Ctrl+S means that you should
hold down the Ctrl key while pressing the S key.
 The program’s features can be accessed through a Ribbon command bar at the top of
the main window. The commands are organized in a series of tabs within the Ribbon. In
this document a command is printed as follows: Tab name: Group name  Button name
 Command name. This means that you should activate the proper tab first and then
press the button Command name, which belongs to the group Group name. If a keyboard
shortcut exists, it is shown in brackets after the command.
Example: View: Change View  Reset View (Space)
 The project data is accessible through the navigation tree on the left side of the

application’s main window. An item of the navigation tree is referenced in the following
way: NT: Tree folder  Sub folder  Tree item.
 Example: View: Visibility  Wire Frame (Ctrl+W)
Your Feedback
We are constantly striving to improve the quality of our software documentation. If you have any
comments regarding the documentation, please send them to your support center:
3DS.com/Support.
9
Chapter 2 – Simulation Workflows
This chapter contains two workflow examples demonstrating the basic features of CST MPhysics
Studio. In the first example, a very simple structural mechanics model of an accelerometer is
created. This workflow describes in detail, how to generate a model geometry, assign material
properties and sources, generate a mesh and run the simulation. Besides, the visualization and
interpretation of structural mechanics results are discussed.
In the second workflow example, a coupled simulation is configured. First, a high frequency
electromagnetic solver calculates the ohmic losses in the walls of an HF-filter. Then, these losses
are imported by the Conjugate Heat Transfer solver in order to model the heating processes in
the filter and its surrounding environment.
Studying these examples carefully will help you to become familiar with many standard
operations that are important when performing simulations with CST MPhysics Studio.
In the subsequent chapters you will find some remarks concerning the extended features of the
solvers omitted in the tutorial part of this documentation.
The following explanations describe the “long” way to open a particular dialog box or to launch a
particular command. Whenever available, the corresponding Ribbon item will be displayed next
to the command description. Because of the limited space in this manual, the shortest way to

activate a particular command (i.e. by either pressing a shortcut key or by activating the command
from the context menu) is omitted. You should regularly open the context menu to check available
commands for the currently active mode.
Simulation Workflow: Structural Mechanics

In this example you will model a simple accelerometer. At first, the geometry of the structure will
be created, and material properties will be defined. Then, boundary conditions will be specified
and the solver will be configured and started. Finally, it will be shown how the solution results
should be interpreted.
The Structure
The following picture demonstrates the spatial structure of a simple accelerometer. It consists of
two fixed flat conductors with a potential difference applied, and a movable conductor between
them.
If the system moves with acceleration, the inertial force pushes the movable conductor towards
one of the fixed ones. The potential difference, e.g., between the conductors 2 and 3 changes
proportionally.
Create a New Project

After starting CST Studio Suite, please select Thermal and Mechanics from the list of installed
modules:
10
After a new CST MPhysics Studio project is created, you can switch the problem type to
Mechanics by selecting Home: Edit  Problem Type  Mechanics .

Open the QuickStart Guide
An interesting feature of the online help system is the QuickStart Guide, an electronic assistant
that will guide you through your simulation. If it does not show up automatically, you can open
this assistant by selecting QuickStart Guide from the dropdown list of the Help button in the
upper right corner.
The following dialog box should now be positioned in the upper right corner of the main view:
The red arrow always indicates the next step necessary for your problem definition. You do not
need to process the steps in this order, but we recommend that you follow this guide at the
beginning in order to ensure all necessary steps have been completed.
Look at the dialog box as you follow the various steps in this example. You may close the
assistant at any time. Even if you re-open the window later, it will always indicate the next required
step.
If you are unsure of how to access a certain operation, click on the corresponding line. The Quick
Start Guide will then either run an animation showing the location of the related menu entry or
open the corresponding help page.
Define the Units

By default, m is selected as the dimensions unit. Please change this setting by selecting Home:
Settings  Units . In the Units dialog, please select mm for dimensions:
11
Model the Structure
The first step is to create a brick.
1. Select the brick creation tool from the main menu: Modeling: Shapes  Brick .

2. Press the Escape key in order to open the dialog box.
3. Fill up the brick size fields as it is shown in the table below.
Xmin -10 Xmax 6

Ymin -1 Ymax 1
Zmin 0 Zmax 0.05
4. In order to select the material, click on the corresponding combo box and select Copper
(annealed). This material is predefined for CST MPhysics Studio projects.
5. Now click the OK button. A new brick has been created:
12
1. Let us explore the material properties of the newly created object. Open the Materials folder
in the Navigation Tree and double-click the item Copper (annealed).

The dialog box Material Parameters: Copper (annealed) appears where various properties of
copper can be modified. Select the tab Mechanics in this dialog box.
13
In this tab you can change the mechanical properties of the selected material. These are the
three most important mechanical properties:
 Young's modulus defines the stiffness of the isotropic elastic material. It is normally
measured in GPa, or kN/mm 2. The typical values vary between 0.01 GPa (rubber) and
over 1000 GPa (diamond). It is important to know the value of this material parameter very
well, since it has a large influence on the accuracy of the solution.
 Poisson's ratio defines the scale of the transverse contraction of a longitudinally stretched
body. This parameter can vary between -1 and 0.5, whereas most of the materials are
characterized by a positive Poisson's ratio.
 Thermal expansion coefficient is the strain of a body if its temperature changes by 1 K.
This value is utilized to compute strain induced by an external temperature field.
2. Now press Cancel and start creating a new brick (Modeling: Shapes  Brick ) with the
following size (please do not press OK yet):
Xmin -6 Xmax 6
Ymin -1 Ymax 1
Zmin 0.05 Zmax 0.7
3. In order to change the material for the new solid, select [Load from Material Library…] in the
Material combo box. The dialog box Load from Material Library appears. Select the material

Steel-1010 and press the button Load.
4. Now press the button OK in the Brick dialog box. A new brick consisting of Steel-1010 is
created.
5. By selecting Modeling: Picks  Picks (S) activate the general pick tool to pick two edges
of the second brick, as shown in the picture below:
14
6. Select Modeling: Tools  Blend  Chamfer Edges in order to chamfer the selected edges.
Enter the chamfer width of 0.65, and keep the default angle of 45° in the appearing dialog box
and click the OK button.
7. Again, open the Brick dialog and enter the following values:
Xmin 6.3 Xmax 7.5

Ymin -1 Ymax 1

Zmin 0 Zmax 0.7
For the new brick a new material should be created. Select [New Material…] in the Material
combo box. The New Material Parameters dialog is shown. In the General tab, enter Plastic
for the Material name.
15
After that, switch to the Mechanics tab in this dialog, select Normal for material Type, set the
Young’s modulus to 2 GPa and the Poisson’s ratio to 0.4.

Confirm your settings with OK.
8. Pick and chamfer one of the upper edges with the chamfer width of 0.7, and keep the default
angle of 45° (Modeling: Tools  Blend  Chamfer Edges ) in order to obtain the following
structure:
16
9. Create the following bricks:
 One of Plastic with the following size:
Xmin 7 Xmax 7.5

Ymin -1 Ymax 1
Zmin 0.7 Zmax 1.5
 Another one of Plastic with the following size:
Xmin -10 Xmax -9

Ymin -1 Ymax 1
Zmin 0.05 Zmax 1.5
 The last one made of Copper (annealed) with the following dimensions:
Xmin -10 Xmax 7.5

Ymin -1 Ymax 1
Zmin 1.5 Zmax 1.6
 The result should be as shown in the following picture:

10. In Navigation Tree to the left of the main document window, open the item Components and
select component1. Afterwards activate Modeling: Tools  Transform .
17
11. In the dialog Transform Selected Object select the operation Mirror, check the boxes Copy
and Unite and set the mirror plane normal to 0, 0, 1, as shown in the following picture:

12. Click OK button. Now the geometric structure setup is complete:
Traction and Displacement Boundaries

After the spatial structure has been built, the next step is to define the displacement and traction
boundaries. Displacement boundaries refer to the surfaces of the model which have been shifted
by a certain distance in a certain direction. To fix a surface at its initial position it is also possible
to set the displacement values to zero.
Traction boundaries are the surfaces where a certain pressure is applied in a certain direction.
Both displacements and tractions are defined as vectors in the Cartesian coordinate system.
In the present example let us fix the both sides of the model and apply a pressure to the middle
electrode, which would mimic the influence of inertial forces during acceleration. The following
steps must be performed:
1. Press the toolbar button Simulation: Boundaries  Displacement Boundary .

2. Select the side faces of the model, as shown in the picture below (you have to select five
faces at x-min and 3 faces at x-max):
18
After pressing the Return key, the dialog box Define Displacement Boundary will appear:

3. Keep the zero values for all the components of the displacement vector and press the OK
button. Now the sides of the model are fixed in space.
4. Press the toolbar button Simulation: Boundaries  Traction Boundary .
5. Double-click the upper surface of the third electrode:
After pressing the Return key, the dialog box Define Traction Boundary will appear:
19
6. Put the value of -2e-6 GPa as the Z-coordinate of the traction vector. This means that the
pressure of 2 kPa is applied towards the negative direction of the Z-axis. This pressure would
roughly correspond to the acceleration of 17*g, or 170 m/s 2, into the positive Z-direction.
Mesh Settings
The structural mechanics solver is quite sensitive to the quality of discretization. In order to obtain
reliable results, the default mesh density needs to be increased. To do this, press the toolbar
button Simulation: Mesh  Global Properties .
In the Mesh Properties – Tetrahedral dialog, change the Cells per max model box edge setting
for Model to 20:

This will increase the density of generated mesh. In order to check the resulting mesh, you may
press the Update button:
Press the OK button to accept the changes and close the window.
Start the Simulation

Finally, after all the settings have been made, it is time to start the mechanical solver. Press the
toolbar button Simulation: Solver  Setup Solver . The structural mechanics solver parameter
dialog box appears.
20
You can click the Help button in order to learn more about the controls in this dialog box. For
now, the default settings are good enough, so just click the Start button. After the calculation has
been started, you can control the execution of the solver in the Progress and Messages windows.
Analyze the Solution of the Tetrahedral Solver

After the mechanical solver finishes the computation, several items appear in the Navigation
Tree.

The directory NT: 1D Results  Adaptive Meshing contains information on the adaptive mesh
refinement performed by the solver. Here you can inspect the number of cells in the mesh for
each iteration step, time used by the solver to generate the solution, as well as the relative error
of the solution. For example, in the picture below you can see the number of degrees of freedom
in the solution for each step of mesh refinement. Please note that the exact values may be slightly
different on different systems.
The directory 2D/3D Results contains the distributions of displacement, strain and stress within
the solution domain. If a temperature distribution has been imported from the thermal solver, it
will be mapped to the tetrahedral mesh and will be available for display here as well.
21
A click on the item NT: 2D/3D Results  Displacement displays a deformation plot of the body
deformation.
Here the original shape of the model is shown semi-transparently whereas the scalar plot of
absolute displacement is shown on the solid deformed shape.
Selecting Arrows from the plot type pull-down menu in the 2D/3D Plot ribbon displays a vector
plot of the body deformation, as shown in the following picture.

Selecting Contour from the plot type pull-down menu displays a scalar plot and enables the vector
component pull-down menu in the 2D/3D Plot ribbon, which contains the following items:
 Clicking on X, Y or Z items displays the corresponding component of the displacement vector.
The example below demonstrates the displacement of the solution domain in the Z-direction.
 The item Abs demonstrates the distribution of the absolute value of displacement within the
solution domain.
 The items Normal and Tangential demonstrate the length of the corresponding projection of
displacement vector onto each body surface.
Navigation Tree item NT: 2D/3D Results  Strain contains the following sub-items:
 Directory Components contains the components XX, YY, ZZ, XY, XZ and YZ of the strain
tensor.
22
 Sub-item Volumetric displays the distribution of the volumetric strain in the model, which
means the relative volume change in each node of the solution domain. The negative values
mean contraction, whereas the positive values mean expansion.
Finally, Navigation Tree item NT: 2D/3D Results  Stress contains the following entries:
 Directory Components contains the components XX, YY, ZZ, XY, XZ and YZ of the stress
tensor.
 The tree-entry Von Mises displays the distribution of von Mises stress within the solution
domain. If this stress at some location is higher than the yield strength of the corresponding

material, plastic deformation takes place in this location. Von Mises stress is always positive.
 The tree-entry Hydrostatic displays the hydrostatic stress distribution, reproducing the change
of the volume in the stressed body. The negative values mean contraction forces.
 The tree-entry First Principal Stress displays the distribution of the largest eigenvalue of the
stress tensor in the solution domain. The first principal stress is the largest tension applied at
the given point.
Another useful feature is the visualization of computation results on a cutting plane. Select 2D/3D
Plot: Sectional View  Fields on Plane from the toolbar to enter this mode. By default, the
cutting plane is perpendicular to the X-axis. Its orientation can be modified from the toolbar by
changing the 2D/3D Plot: Sectional View  Normal setting. Also the position of the cutting plane
can be changed in this way.
In the following picture the distribution of the absolute value of displacement vector is shown on
the cutting plane perpendicular to the Y-axis.
23
Vector fields can be visualized on a cutting plane in the same manner. Just select the Arrow plot
type in the 2D/3D Plot ribbon (of course, for a plot with vector data like Displacement). In this
case the Fields on Plane mode stays activated.
Summary
This example should have given you an overview of the key concepts of CST MPhysics Studio.
Now you should have a basic idea of how to do the following:

1. Model the structures by using the solid modeler;
2. Define and modify various material parameters;
3. Assign displacement and traction boundaries;
4. Start the structural mechanics solver;
5. Explore the results of adaptive mesh refinement;
6. Visualize various distributions delivered by the mechanical solver;
7. Visualize the deformation of the mesh and scale it.
If you are familiar with all these topics, you have a very good starting point for further improving
your usage of CST MPhysics Studio.
For more information on a particular topic, we recommend you browse through the online help
system which can be opened via the Help button in the upper right corner. If you have any
further questions or remarks, do not hesitate to contact your technical support team. We also
strongly recommend that you participate in one of our special training classes held regularly at a
location near you. Ask your support center for details.
Simulation Workflow: Coupled EM-CHT Simulation

Coupled simulations are the main application field for CST MPhysics Studio. The new parametric
multi-physics workflow simplifies the management of coupled simulation projects, which share
the same model geometry (called the Master Model). Changes in the Master Model are directly
transferred to the subprojects. In addition, this workflow supports the definition of global
parameters, which are shared between the subprojects, as well as the usage of parameter
sweeps or optimization sequences.
The typical workflow is demonstrated with an EM-Thermal coupled project. The simulated device
consists of a filter placed on a horizontal support and surrounded by air. The EM solver is first
used to perform a frequency domain analysis of the filter and to calculate the field distribution
and the ohmic losses. The energy lost by the filter is transformed into heat which increases the
filter temperature. The conjugate heat transfer (CHT) solver is then used to compute the
temperature increase. The ohmic losses are imported as heat sources into the thermal simulation
and a thermal analysis of the filter is performed by including the cooling effect of the surrounding
air.
24
EM-Thermal Link Set-up
Please open the project “Combline Filter Draft” located in the Component Library. To access the
example, please select the File tab, then select Component Library, type “Combline” into the
search field on the top right and press Enter:
To open the project you have to download a copy first, by clicking on the Download symbol. Once
this is done you are ready to open the example by clicking on the Open Project symbol.

Start the automatic creation of a coupled electromagnetic/thermal computation by selecting
Home: Simulation  Simulation Project  EM-Thermal Coupling  Uni-directional.
A dialog box appears to create the first part of the EM-Thermal link:
25
The EM simulation project is named EM1 and will be performed by the frequency domain solver
of MWS. Select High Frequency as Project type and Frequency Domain as Solver type. All the
settings from the master model can be inherited by selecting its schematic block as the reference
model.

After you click the OK button, a new simulation project called EM1 is first created and added to
the Tasks folder in the Navigation Tree in the Schematic view; then a dialog box appears to
create the second part of the EM-Thermal link:
In the dialog box, the project type Thermal & Mechanics is already chosen, so only select the
thermal solver type Conjugate Heat Transfer and rename the project to CHT. After pressing OK,
a thermal simulation task using the CHT solver is created.
Loss Import
In the next step, you are invited to define the frequency at which the thermal losses should be
computed and exported. The losses directly exported by the EM solver are by default calculated
for an input peak power of 1W. The simulated device however may be operated at a different
26
input power therefore the exported losses must be proportionally rescaled. For an operational
input power of 100W, assign the value 100 to the Scaling factor for losses entry:
Click OK. The corresponding monitors and field imports are configured automatically in both
simulation projects. Now you may switch to the thermal project (select the CHT project tab in the

main view) and configure additional material properties, necessary thermal sources, boundary
conditions and calculation parameters.
In the navigation tree a field source called EM1 (named after the name of the EM project of the
EM-Thermal link) has been automatically added and configured. Edit it to reconfigure it if
necessary. The exclamation mark indicates that losses are missing because the EM1 simulation
has not yet been performed.
Background and Boundary Conditions

To take into account the effect of natural convection it is necessary to create some space around
the device so that the airflow induced by heated device can be simulated:
Some of the materials contained in the original model are missing thermal properties. In order for
the CHT solver to work properly, the density, heat capacity and thermal conductivity of the
background and of all the solids must be defined (>0). In addition, the dynamic viscosity of the
background material must be specified. To include the contribution of radiation from a solid, the
emissivity has to be specified as well. By default, radiation calculation is not activated but can be
enabled in the solver parameter dialog (see section Solver Parameters).
27
The background material properties (Simulation: Settings  Background ) need to be copied
from the material “Air”. To do this click on the Properties… button and then on the Copy Properties
from Material… button in the General tab of the material dialog.
Select the Thermal tab and check the properties before closing the dialog with OK.

Note: solids made of material PEC will be automatically replaced in the solver by the material
Copper (annealed).
Make sure that the material named “MWSSCHEM1/dielectric” has the following thermal
properties (the density value can be entered under the Density tab):
28
Please check the material named “MWSSCHEM1/brass” in the same manner:
29
Open Simulation: Settings  Boundaries to exploit the symmetry of the model with respect to
the YZ plane and set-up the YZ symmetry boundary condition:
Assuming the device is positioned horizontally, the horizontal support is modeled as an adiabatic
wall while the other sides of the computational domain are set to open:

Mesh Settings
Please change the mesh type to CFD (Simulation: Mesh  Global Properties  CFD) and
open the mesh properties dialog. Adjust the Minimum cell setting to a fraction of 40 for the
maximum cell in the model.
30
Solver Parameters
Please change the default temperature unit to Celsius in the project Units dialog (Home: Settings
 Units ) to have the results presented in Celsius later.
Then open the solver parameter dialog (Simulation: Solver  Setup Solver ). Activate the
Gravity check box to simulate the effect of natural convection. Adjust the Ambient temperature
unit to Celcius and specify the ambient conditions of 20°C.
If Radiation is turned on, the radiation temperature can be used as reference temperature when
the contribution of open boundary conditions to radiation is taken into account.. Please note that
we perform this simulation without radiation in order to reduce the computation time for this
tutorial.
31
Open the CHT Solver Special Settings dialog by pressing the button Specials… and limit the
Number of iterations to a maximum of 80 in order to shorten the otherwise lengthy simulation
time. Please note that the results obtained after 80 iterations are not fully converged. If more
accurate results are desired change the number of iterations to automatic calculation (i.e. switch

off the Maximum checkbox). With current settings, the overall simulation time should be less than
20 minutes.
32
Apply all settings with the OK or Apply buttons before closing the CHT Solver Special Settings
and Conjugate Heat Transfer Solver Parameters dialog box.
Coupled Run
Switch back to schematic of the master project (first tab) and therein to the Schematic view (select
the appropriate tab at the bottom of the main view). Press the button Home: Simulation  Update
. At first, the EM calculation will be started. Next, the losses will be computed. Finally, these
losses will be imported into the thermal project, and the thermal calculation will be performed.
Alternatively, right click on NT: Tasks  Coupled EM-Thermal1 and Update the task.

A progress bar will appear in the progress window which will update you on the task progress.
You can activate this window by selecting View: Window  Windows  Progress Window.
Information text regarding the simulation will appear above the progress bar. The most important
stages are listed below for the CHT solver:
1. Updating tasks: 1of 1: the selected task includes the previously created EM and CHT
simulation.
2. …. the EM simulation is performed….
3. CHT solver: Surface mesh generation: the solid surfaces are triangulated.
4. CHT solver: Octree grid generation: the CFD mesh is constructed by using the solid
surface triangulations.
5. CHT solver: Importing surface/volume losses: the losses from the EM simulation are
imported and mapped into the CFD mesh.
6. CHT solver: Upgrade grid: inactive cells are removed from the CFD mesh.
7. CHT solver: Iterations: the simulation is performed.
Simulation Results
Once the EM simulation has been completed please leave the schematic and return to the CHT
simulation. Follow the progresses of the CHT simulation by looking at the convergence monitors
in the NT: 1D Results  Convergence monitors  Equation residuals and NT: 1D Results 
Convergence monitors  Equation balances.
The simulation completes 80 iterations before stopping. The following dialog box pops up
because the simulation has not fully converged (i.e. several convergence criteria have not been
met due to the low maximum number of iterations):
33
Choose Stop and save the results and press OK.

To visualize the loss imported from the EM simulation, select NT: 2D/3D Results  Heat source
densities and a cut plane, for instance X=0. Please note that the losses can only be visualized
on cut planes (check ribbon 2D/3D Plot: Sectional View  Fields on Plane). Observe that the
losses are the highest on the walls of the coaxial feeds and of the cylinders.
Once the simulation has stopped, visualize in the same cut plane the temperature by selecting
NT: 2D/3D Results  Temperature.
34
The temperature increases are the highest where the losses are also the highest. The air in
contact with the walls of the filter heats up and carries the heat away which cools down the filter.
One can observe that the simulation has not converged to a steady-state solution in the whole
domain because the heat carried by the air flow has not yet reached the top boundary of the

computational domain. Still, the simulation has enough progressed to show a correct temperature
distribution inside the filter.
The CHT solver takes into account the air cooling effect by simultaneously calculating the heat
transfer in the fluid and solid domains and the air flow caused by the temperature gradients and
gravity. This key feature differentiates the CHT solver from the thermal solvers which do not solve
for the air flow and thus can simulate neither natural nor forced convection.
The air flow can be visualized by selecting NT: 2D/3D Results  Velocity
The velocity vector plot shows the air circulating inside the filter as well as the heated air
ascending and being replaced by air at ambient temperature.
Of course, this short introduction does not cover all details about the possibilities of coupling
between various CST Studio Suite projects. For more information, please refer to the online help
tutorials.
35
Chapter 3 – Solver Overview
Solvers and Sources
Various simulation types differ in the definition of materials, boundary conditions and sources.
The way to define materials in CST MPhysics Studio is quite similar for all solvers, whereas there
are larger differences in the definition of sources and boundary conditions. For this reason, an
overview of the sources, loads and boundaries for each solver are explained below.
Mechanical Solver:
 Displacement boundary: Simulation: Boundaries  Displacement Boundary
 Traction boundary: Simulation: Boundaries  Traction Boundary
 External temperature and/or force distribution:
Simulation: Sources  Field Import
Thermal and Conjugate Heat Transfer Solvers:

 Fixed temperature: Simulation: Sources and Loads  Temperature Source
 Heat source: Simulation: Sources and Loads  Heat Source
 Volume heat source: Simulation: Sources and Loads Volume Heat Source
 Thermal losses from an electromagnetic or particle simulation:
Simulation: Sources and Loads  Thermal Losses
 Thermal contact resistance:

Simulation: Sources and Loads  Contact Properties
 Convection and radiation at surfaces:
Simulation: Sources and Loads  Thermal Surface
 Initial temperature distribution for a transient calculation:
Simulation: Sources  Field Import
Conjugate Heat Transfer Solver:

 Fan: Simulation: Sources and Loads  Fan
 Two-resistor component model:
Simulation: Sources and Loads  Two-resistor model
Mechanical Solver
The mechanical solver is a tetrahedral based solver for structural mechanic problems. Its main
application is computing deformations driven by thermal expansion and external forces. The
deformation results can be used for a subsequent High Frequency Electromagnetic analysis with
the tetrahedral based frequency domain solvers from CST Microwave Studio.
Refer to the chapter Simulation Workflow for a description of the basic features. The import of
temperature and force density distributions is described in the section Workflow for Coupled
Simulations.
Thermal and Conjugate Heat Transfer Solvers

CST MPhysics Studio includes a thermal and a conjugate heat transfer (CHT) solver. The thermal
solver is optimized to simulate thermal conduction in the steady state and transient regime and
supports hexahedral and tetrahedral grids. The CHT solver is a CFD based heat transfer solver
capable of solving thermal conduction, convection and radiation simultaneously in the steady
state regime. The main applications of these solvers include solving steady state or transient
temperature problems resulting from various types of losses.
In addition, the thermal and CHT solvers are also well suited to compute standalone thermal
problems. The following section demonstrates the most important aspects of a thermal simulation
with CST MPhysics Studio.
Background Material
The first step for setting up a thermal simulation is to define the units for temperature and
dimension, like it has been described in the chapter Simulation Workflow. Afterwards an
appropriate background material should be selected. Open the material background properties
dialog box by selecting Modeling: Materials  Background :
36
For thermal problems, the background material is set to Air (thermal conductivity: 0.026 WK-1m-
1, heat capacity: 1.005kJK-1kg-1, density: 1.204 kg/m 3 and dynamic viscosity: 1.84e-5 Pa.s at
normal conditions). These settings may be changed by selecting the Material type (Normal is
advisable in most cases), afterwards opening the material dialog box by pressing Properties...
and select the Thermal property page:
The easiest way to assign the necessary values is to copy the properties from an existing material
in the material library. Press the Copy Properties from Material… button in the General tab, select
[Load from Material Library…] in the Copy Properties from Material dialog box:
37
Now choose the desired material from the material list.
Material Properties
The material parameters for a thermal problem can be defined inside the material parameters
dialog box: Modeling: Materials  New/Edit  New Material . Select the Thermal tab.
It is necessary to specify a thermal conductivity to perform a thermal or conjugate heat

transfer simulation. In the Thermal tab please specify a thermal conductivity for your material
in W K-1 m-1 in case a Normal or Anisotropic thermal material Type has been selected. If a
temperature dependent thermal conductivity, heat capacity and/or blood flow coefficient should
be taken into account, activate the checkbox Nonlinear and define the material curve by entering
the corresponding dialog box via Properties…
Please note that the conjugate heat transfer solver only supports isotropic and constant
material parameters.

If you select a PTC (Perfect Thermal Conductor) type, an infinite thermal conductivity is assumed.
A body with PTC material assigned always has a uniform temperature.
Please note that the conjugate heat transfer solver replaces PTC with copper.
For transient thermal problems (see also the next chapter) and the conjugate heat transfer
solver the heat capacity and the material density must be specified. These parameters
determine how much energy per Kelvin is stored in a certain amount of mass or volume:
38
Specify the material emissivity when radiation is enabled in a conjugate heat transfer simulation.
Because the thermal diffusivity plays an important role for the transient simulation process, it is
shown here as well. The diffusivity can be calculated from the thermal conductivity, the heat
capacity and the material density as follows:
k
 ,
  cP 1000
where
: Diffusivity [m² / s]
k: Thermal conductivity [W / K /m]
: Density [kg / m³]
cP: Specific heat capacity [kJ / K / kg]
Nonlinear heat capacity can be used for simulation of material phase change in transient
computations. This can be achieved by a local increase of heat capacity for a small interval of
temperatures. For more information on simulation of phase changes, please refer to the online
help.

For simulations which involve biological materials, heating mechanisms of living tissue can be
taken into account (see also: Bioheat Source below). In addition, it is possible to define a
convection coefficient for surface materials of human voxel models (typically: skin).
The Flow Resistance material parameter is only supported by the conjugate heat transfer solver.
It is used to model the fluid flow behavior across a screen without having to mesh the screen
geometry.
A flow going through a sheet with a planar flow resistance experiences a pressure drop which
can be expressed as follows:
  
P  0.5  f    u  n  u ,
 
where f is the dimensionless loss coefficient, n is the sheet local normal and u the flow velocity.
A flow going through a volume resistance experiences a pressure gradient which can be written
as follows:
Pj  0.5     f ij  u j u j ,
j
where f ij is the loss coefficient tensor per unit length and u j is a velocity component in the global
coordinate system (X,Y,Z).
The loss coefficient tensor is defined with respect to a local coordinate system (U’,V’,W’) and
transformed into a 3x3 tensor in the global coordinate system.
A Flow Resistance assigned to a surface uses the specifications of the sheet properties group
whereas a Flow Resistance assigned to a solid uses the specifications of the solid properties.
39
Boundary Conditions
The boundary conditions for the thermal and conjugate heat transfer solver can be defined in the
Thermal Boundaries tab of the Boundary Conditions dialog box (Simulation: Settings 
Boundaries )
For Steady State and Transient Thermal Solvers:
The thermal boundary offers the following choices of boundary conditions:
For “isothermal” and “open” boundaries the temperature settings may be assigned by pressing
the corresponding button […]. This button opens the dialog Boundary Settings, in which the
temperature value can further be configured, for example, by assigning of a fixed or floating
temperature. By default, the option Unset is selected, which means the boundary is considered
as a PTC surface without sources assigned.
40
For the "open" boundary condition, it is assumed that the temperature approaches the predefined
value with increasing distance from the structure. Apply this type of boundary condition if thermal
conduction through the surrounding background material plays an important role for your
problem. In order to consider thermal convection effects on the structure, Thermal surface
properties (see p. 44) should be used.
When no heat flow leaves the computational domain through a boundary, use the "adiabatic"
boundary condition. In case the conductive heat flow of an open structure can be neglected, you
can use these boundary conditions instead of “open” boundary conditions (if radiation or
convection effects dominate).
The "isothermal" boundary condition forces the temperature to be constant at this boundary. As

a consequence, the tangential component of the heat flow density is forced to be zero here.
The following table shows an overview, where T is the temperature and Q is the heat flux density:
Temperature (T) Heat Flow (Q)

Isothermal T = const (fixed or floating) Q tangential = 0
Adiabatic d T / dN = 0 Q normal = 0
Open Lim R→∞ (T) = const (fixed or
floating)
The picture below illustrates an example of how thermal fields are influenced by the different
boundary types. It shows a metal sphere at a constant temperature, which is surrounded by a
material with constant thermal conductivity.
For Conjugate Heat Transfer Solver:
The conjugate heat transfer solver supports similar types of boundary conditions. It is however
important to note that it interprets these boundary conditions differently, in particular for the case
of open boundaries.
41
User input for isothermal walls: temperature, emissivity and friction (no-slip/slip) at the boundary
wall. The reference temperature used for radiation is the wall temperature.
User input for adiabatic walls: friction at the boundary wall (no heat exchange, zero emissivity).
User input for symmetrical boundaries: none (no friction, no heat exchange, zero emissivity).

User input for open boundaries: flow temperature, flow velocity or flow gauge pressure. An
open boundary allows flow to enter and leave the domain, which could be used to model the flow
and thermal behavior of an inlet or of an outlet specified by a pressure gauge or a velocity. If the
flow temperature is unknown, which is the case for outlets or if the flow direction is unknown set
the temperature to unset.
The emissivity is set to 1. The reference temperature used for radiation is the radiation
temperature defined in solver parameter dialog.
Sources and Loads

The thermal and conjugate heat transfer solvers can handle several types of sources or loss
mechanisms, which are listed below:
Temperature Source
This source is available via Simulation: Sources and Loads  Temperature Source . This
source type can be assigned to a surface of an object with PTC material properties or any other
material with non-zero thermal conductivity. You can choose between a fixed temperature value
and a floating temperature. A floating temperature is a uniform temperature distribution with zero
heat flow from or into the associated surface. Besides, for the transient solver an initial
temperature source can be defined, which is taken into account only for generation of the initial
temperature distribution and ignored during the transient solution.
Heat Source
This source is available via Simulation: Sources and Loads  Heat Source
42
When assigned to a solid with a non-zero thermal conductivity source and that is neither PTC
nor PEC it defines the thermal power evenly released within the solid. The user may define the
total power released within the solid (Total) or the volume heat density (Density).
When assigned to a solid that is either PTC or PEC it defines the total heat flow coming from the
solid surface. Therefore, a heat source with zero heat flow and a floating temperature are
identical.

Thermal Loss Distribution
This source is available via Simulation: Sources and Loads  Thermal Losses . Thermal
losses can occur inside materials with finite conductivity, on surfaces of good conductors, inside
dispersive materials or at materials where particles hit the surface. These loss distributions can
be imported and used as thermal sources inside thermally conductive materials. If previously
calculated loss distributions are present, you can edit setting by reopening the dialog box
(Simulation: Sources and Load  Thermal Losses ).
43
It is possible to choose source fields from the same project or from an external project. The
following table shows a list of loss types and which solver from the CST Studio Suite can create
these losses.
Type of loss Created by

Ohmic Transient Solver ( ), Frequency Domain Solver ( ),
(electric vol. losses) Eigenmode Solver ( ), J-Static Solver ( ),
LF-Solver ( ), PIC Solver ( ), Wakefield Solver ( ),
IR-Drop Solver ( )
Lossy metal Transient Solver ( ), Frequency Domain Solver ( ),
(surface losses) Eigenmode Solver ( ), LF-Solver ( ), PIC Solver ( ),
Wakefield Solver ( )
Dispersive Transient Solver ( ), Frequency Domain Solver ( ),
(electric and PIC Solver ( ), Wakefield Solver ( )
magnetic vol.
losses)
Crashed particles Tracking Solver ( ), PIC Solver ( )

For further details, refer to the online help.
Thermal Surface Properties

Thermal surface properties are available via Simulation: Sources and Loads  Thermal
Surface .
Thermal surface properties can be assigned to surfaces of thermally conductive materials. A

thermal surface property definition describes the radiation and convection losses from a surface:
The Emissivity  is a dimensionless constant between 0 and 1 which describes the radiation
capability of the selected surface
QRadiation  ASurface      (T 4  TReference

4
),
44
whereas QRadiation stands for the radiated power, T for the surface temperature, TReference for the
reference temperature, which can be equal to ambient or user-defined,  for the Stefan-
Boltzmann constant and ASurface for the area for the selected surfaces. An emissivity value  = 0
means that the surface does not lose thermal power by radiation. A value of 1 means that the
thermal power emitted by the surface equals to that of a black body at the same temperature.
The Convective heat transfer coefficient h describes convection processes between a fluid and
the surface of conductive materials:
QConvection  ASurface  h  (T  TReference )

where QConvection denotes the power, T the solid surface temperature, TReference the reference
temperature in the fluid and ASurface the area for the selected surfaces.
The thermal surface properties dialog includes additional options for the conjugate heat transfer
solver. The emissivity of the solid defined by the emissivity of its material can be overwritten by
a surface emissivity for the assigned surface. In addition, the local fluid temperature can be used
as the reference temperature when convection is prescribed by a heat transfer coefficient.

Fan (not supported by Thermal solver)
Axial fans are available via Simulation: Sources and Loads  Fan . They are defined by their
entry and exit faces. The entry and exit faces must belong to the same lump of the same solid.
They can be either assigned both to the same surface if the fan is planar or translated from each
other. Note that a planar (infinitely thin) fan can only be created on an outer boundary and can’t
be created in the interior domain. A non-planar (thick) fan can be created either on the outer
boundaries or in the interior domain.
The axial fan behavior can be specified as follows:
45
The fan characteristics (i.e. fan curve, volume flow rate or stagnation pressure) are given for a
quoted speed. The fan however can be operated at a different speed. The derating factor is the
ratio of operating speed and quoted speed and is a dimensionless value between 0 and 1. If the
derating factor is 0.8, the operating speed will be 80% of the quoted speed and the fan
characteristics and the dissipated heat will be adjusted accordingly. The flow temperature can be

controlled either by specifying a fixed temperature or the amount of heat dissipated from the flow
going through the fan.
The fan characteristics are given by a fan curve defined either by one or two or more points. If a
fan curve has only one point its type is Fixed Volume and is specified by entering its volume flow
rate. If the fan curve has two points its type is Linear and is specified by entering its volume flow
rate for zero pressure and its stagnation pressure. If the fan curve has more than two points its
type is Nonlinear and each point can be entered individually by clicking on the Curve button.
Two-resistor component model (not supported by Thermal solver)

Two-resistor component models are available via Simulation: Sources and Loads  Two-resistor
model .
The two-resistor component model can be used to approximate the thermal behavior of single-
die packages that can be effectively represented by a single junction temperature.
The model is based on the block-and-plate method described in the Two-Resistor Compact
Thermal Model Guideline specified in the JEDEC standard JESD15-3.
The 3D representation of the two-resistor model is shown below:
The input parameters of the model are the case node and board node temperatures, which are
provided by the heat transfer solvers, and the junction node dissipated power together with the
junction-to-case Rjc and the junction-to-board Rjb thermal resistances that must be provided by
the user.
46
The output parameter of the model is the junction node temperature. In the 3D representation,
the package represents the junction node thermal resistance whereas the upper package and
the lower package surfaces represent the junction-to-case thermal resistance and the junction-
to-board thermal resistance, respectively. The package lateral sides are assumed to be insulated
(no heat transfer).
The two-resistor component model has been extended by making it possible to define contact
properties on the upper package surface. This is useful when a heatsink covers the upper surface
package.
Bioheat Source (not supported by CHT solver)

As described above it is possible to assign biological properties to a material. Two different
heating mechanisms are available:
The Bloodflow coefficient determines the influence of blood at a certain temperature TBlood inside
the tissue volume V.
QBloodflow  V  C Bloodflow  (TBlood  T )
Depending if the current temperature value T is higher or lower than the blood temperature this
mechanism cools or heats the surrounding material. The blood temperature value can be edited
inside the Specials dialog box of the thermal solvers (Simulation: Solver  Setup Solver 
Specials or Simulation: Solver  Setup Solver  Specials).

An important mechanism of the local thermoregulation in living tissues is an increased bloodflow
coefficient with rising temperature due to the widening of blood vessels (vasodilation). In order to
match clinical studies, the bloodflow coefficient is typically assumed to change exponentially with
increasing temperature. The parameters of this dependency can be set in the Nonlinear Thermal
Material Properties dialog, accessible through the Nonlinear Properties button in the Thermal tab
of the Material Properties dialog. For more information about these parameters please refer to
the online help.
The Basal metabolic rate describes the amount of heat QMetabolic which is produced by tissue per
volume V.
QMetabolic  V  CMetabolic
Thermal Contact Properties

Thermal contact properties can be defined via Simulation: Sources and Loads  Contact
Properties . A contact item is equivalent to a thin layer of thermally conductive material at the
interface between two (or several) solids. It can be characterized either by lumped parameters
(absolute thermal resistance [K/W] or thermal resistance per unit area [K∙m2/W] as well as thermal
capacitance [J/K]), or by its thickness and the thermal properties of material assigned. Both
definitions are equivalent and can be easily converted into each other:
Absolute thermal resistance (K/W):
Thermal resistance per unit area (K∙m2/W):
Thermal capacitance (J/K):
Here Rθ represents the absolute thermal resistance, rθ the thermal resistance per unit area, C
the thermal capacitance of the contact layer. In the material-based representation, thermal
conductivity k, specific heat capacity cP, material density ρ and layer thickness l are used. The
contact area A is calculated by the solver.
47
The advantage of contact properties definition through lumped parameters is the ease and
transparency of the parameter values. Besides, the absolute thermal resistance is independent
from the contact area A which may vary in case of solid intersections or depending on the mesh
settings. On the other hand, the material-based definition offers more flexibility, for example it
supports nonlinear material properties.
Thermal contact properties are only supported by tetrahedral-based thermal solvers and the
conjugate heat transfer solver.

Moving Media (not supported by CHT solver)
For each solid containing a non-PTC thermal conducting material, a moving media velocity vector
may be assigned via Simulation: Motion  Moving Media .
This vector defines the velocity with which the material comprising the solid is moving relatively
to the sources and solid geometry. A typical example would be a very long tube moving through
a coil for the purpose of induction heating.
If a velocity vector has been assigned to any solid, the solver saves important information about
the distribution and maximum of Peclet number in order to control the solution quality.
Only tetrahedral-based thermal solvers support this feature. In the transient solution, the moving
media velocity vector may be made time-dependent by assigning Excitation Signals to its
components.
You can find more detail about moving media in the online documentation.
Monitors at Points
The monitors of this kind record scalar values that are defined at a point (e.g. the x-component
of the heat current density at a fixed position). You can create these monitors via Simulation:
Monitors  Monitor at Point .
48
Steady state thermal solver evaluates the temperature values at the monitor points and saves
them as 0D data into the Navigation Tree under NT: Thermal Solver  Temperature 0D 
<monitor name>. Besides, if adaptive mesh refinement is turned on, the tetrahedral-based steady
state solver records the temperature value after each refinement step and saves it under NT:

Adaptive Meshing  Temperature 0D  <monitor name>.
Transient thermal solver records the temperature values at the monitor points during the whole
solution time interval.
Two additional types of monitor at point are available for the conjugate heat transfer solver. The
Pressure and Velocity types evaluate, respectively, the pressure and velocity at the monitor point
at each iteration.
The conjugate heat transfer solver saves the values of the monitor points as 1D data into the
Navigation Tree under NT: 1D Results  Monitors at Points  <monitor name>.
The conjugate heat transfer solver can use the point monitors activated in Simulation: Setup
solver: Accuracy: Custom stop criteria to detect the convergence of the solver.
This monitor type is similar, although not identical, to Probes available within CST Microwave
Studio.
Monitors on Faces
The monitors of this kind record scalar values defined on a surface. You can create these
monitors via Simulation: Monitors  Monitor on Faces .
Two types of monitors on face are available. The type flow flux is used to monitor the fluid flow,
consequently the monitor surfaces must not change the flow and must be borrowed from a
dummy solid. A dummy solid is either a solid whose material is exactly the same as the
background material or a solid not considered for simulation but considered for the bounding box.
If necessary, adjust the local mesh properties of the dummy solid to match those of the
background to avoid unwanted mesh refinements around the dummy solid.
49
The flow flux monitor calculates the mass flow rate, the energy flux and the bulk temperature
through the monitor surfaces, respectively defined as:
𝑚̇ = ∯ 𝜌𝐮 ∙ 𝐝𝐀
𝑄̇ = ∯ 𝜌𝐶𝑝 𝐮(𝑇 − 𝑇𝑎𝑚𝑏 ) ∙ 𝐝𝐀

1
𝑇𝑏 = ∯ 𝜌𝐶𝑝 T𝐮 ∙ 𝐝𝐀
𝑚̇𝐶𝑝
The type solid flux is used to monitor the heat flux and the heat transfer coefficient at solid/fluid
interfaces, consequently the monitor surfaces must be borrowed from a solid considered for
simulation and considered for the bounding box and whose material is different from the
background material:
𝑃 = ∯ −𝑘 ∙ ∇𝑇 ∙ 𝐝𝐀

The monitors on faces are evaluated at each iteration and the surface quantities are saved as
1D data into the Navigation Tree under NT: 1D Results  Monitors on Faces  <monitor name>.
The conjugate heat transfer solver can use the face monitors activated in Simulation: Setup
solver: Accuracy: Custom stop criteria to detect the convergence of the solver.
3D Field Monitors
Note: the conjugate heat transfer solver stores the simulation results obtained for the whole
computational domain and ignore the 3D field monitors.
In contrast to steady state solvers, field distributions delivered by transient solvers need to be
requested by the user in advance by defining Field Monitors via Simulation: Monitors  Field
Monitor . A dialog box opens where the type of the field, the start time and the sample step
width can be defined:
Three field types are available: Temperature, Heat Flow Density and CEM43. The latter monitor
represents the distribution of Cumulative Equivalent Minutes at 43°C, which is commonly used
to detect the damage of biological tissues exposed to strong electromagnetic fields. After the
50
solver run has been completed, the recorded result can be accessed via the 2D/3D Results folder
in the Navigation Tree. The scalar or vector field can be animated over the defined time period.
Steady State Thermal Solver Parameters

After the thermal problem has been defined, the steady state solver dialog box can be opened
(Simulation: Solver  Setup Solver ):

Before starting the solver, it is advisable to look at the Ambient temperature, which is by default
the reference temperature for the radiation and convection models as well as for the open
boundary conditions. Moreover, this temperature may be assigned to PTC regions without user-
defined temperature or heat sources.
If Bioheat properties must be adjusted, one can open the Specials dialog:
This also applies to the transient thermal solver. For further details, please refer to the online
help.
51
Excitation Signal Settings
For some transient thermal simulations, it is necessary to define time domain excitation signals
to model, for example, time varying heat sources. A new signal can be defined via Simulation:
Sources and Loads  Signal  New Excitation Signal. A dialog box opens where a signal
type, its parameters and a name can be set.

The parameters of the signal depend on the individual signal type and are described in the online
help. The parameter Ttotal must be set for almost all signal types and defines the size of the
definition interval. For time values larger than Ttotal the signal is, in general, continued by a
constant value. It is also possible to import a signal or to create a user defined signal or to select
a pre-defined signal from the signal database.
All defined signals are visible in the Signal folder in the Navigation Tree and can be displayed by
selection in the Navigation Tree:
Transient Thermal Solver Settings

You can switch between the steady state and transient thermal solvers by selecting either
Home: Simulation  Setup Solver  Thermal Steady State Solver or

Home: Simulation  Setup Solver  Thermal Transient Solver .
After selecting the transient solver, the solver parameters dialog box can be opened by clicking
on the icon in the Home or the Simulation ribbon (Simulation: Solver  Setup Solver ). Before
starting the transient thermal solver, a valid Simulation duration time must be entered:
52
Most source types can be weighted with a previously defined excitation function, when pressing
the Excitations button:
For each source, a signal can be assigned via a drop down list. The same signal can be assigned
to several sources. Optionally, an individual time delay  t can be defined for each source. The
resulting time dependent excitation f is the product of the source value v (e.g. the temperature)
and the (possibly shifted) assigned signal s :
f (t )  s(t  t )  v .
The initial temperature distribution can be defined in the Select Start Temperature dialog, which
can be called by pressing the Start temperature: Settings button. The default setting is to assign
the ambient temperature everywhere except regions with temperature sources. Alternatively, it
is possible to assign the solution of the steady-state problem with initial source values as well as
import a temperature distribution from an external thermal solution.
53
The solver parameters dialog box also allows changing the ambient temperature in the currently
active unit. Moreover, the accuracy settings are accessible via the Accuracy button and can be
edited in case simulation speed or accuracy is not sufficient. For further details, please refer to
the online help.
Result Types
After a steady state thermal simulation run has been completed successfully, new result
entries appear in the navigation tree:

The directory 1D Results contains the convergence curve, heat flow values for the heat sources
as well as power scaling values for imported fields.
In the directory 2D/3D Results, beside the scalar temperature field the heat flow density can be
seen, which is a vector field showing the heat flow inside thermally conductive materials.
Moreover, a text file is written where the total heat flow for every source is listed. In case field
losses were imported, further information like interpolated loss distributions as well as the scaling
factor is presented.
The transient thermal solver creates a different output in the navigation tree:
54
Temperature & total Heat Flow on PTC
based sources vs. time are recorded
automatically.
Monitor at Point: field values vs. time at one

point.
1D solver statistics: created automatically
by the transient thermal solver.
3D results from previously defined

time domain monitors and
automatically created start
distributions.

If time domain temperature monitors have been defined for the transient thermal solver, the
associated results will be listed under 2D/3D Results as well. In addition, a couple of time signals
are added to the 1D Results section:
 ThermalTD / Energy describes the total amount of energy in the computation domain
vs. time.
 ThermalTD / Timesteps carries information about the time-step-width vs. computation
step of the adaptive time-stepping scheme.
 ThermalTD / Timescale shows how the simulated time evolves vs. computation steps.
 ThermalTD / Power shows the total amount of power entering/leaving the thermal
conductive regions.
These 1D signals can be updated during the simulation process by selecting the tree item and
pressing 1D Plot: Plot Properties  Update Results or the F5 key.
The conjugate heat transfer solver produces the following results
55
The 1D Results contain solution convergence, point and face monitors as well as performance
data, plotted against iterations to give user insights into convergence and solutions.
The 2D/3D results contain velocity, temperature, pressure and heat source densities data, which
can be updated during the iteration process using Plot Properties  Update Results or the F5
key.
56
Chapter 4 – Finding Further Information
After carefully reading this manual, you will already have some idea of how to use CST MPhysics
Studio efficiently for your own problems. However, when you are creating your own first models,
some questions may arise. In this chapter, we give you a short overview of the available additional
documentation.
The Quick Start Guide

The main task of the Quick Start Guide (not available for Conjugate Heat Transfer solver) is to
remind you to complete all necessary steps in order to perform a simulation successfully.
Especially for new users – or for those rarely using the software – it may be helpful to have some
assistance.
The QuickStart Guide is opened automatically on each project start if the checkbox File: Options
 Preferences  Open QuickStart Guide is checked. Alternatively, you may start this assistant
at any time by selecting QuickStart Guide from the Help button in the upper right corner.
When the QuickStart Guide is launched, a dialog box opens showing a list of tasks, where each
item represents a step in the model definition and simulation process. Usually, a project template
will already set the problem type and initialize some basic settings like units and background
properties. Otherwise, the QuickStart Guide will first open a dialog box in which you can specify
the type of calculation you wish to analyze and proceed with the Next button:

As soon as you have successfully completed a step, the corresponding item will be checked and
the next necessary step will be highlighted. You may, however, change any of your previous
settings throughout the procedure.
In order to access information about the QuickStart Guide itself, click the Help button. To obtain
more information about a particular operation, click on the appropriate item in the QuickStart
Guide.
Online Documentation
The online help system is the primary source of information. You can access the help system’s
overview page at any time by choosing File: Help  Help Contents . The online help system
includes a powerful full text search engine.
In each of the dialog boxes, there is a specific Help button, which opens the corresponding
manual page. Additionally, the F1 key gives some context sensitive help when a particular mode
is active. For instance, by pressing the F1 key while a basic shape generation mode is active,
you can get information about the definition of shapes and possible actions.
When no specific information is available, pressing the F1 key will open an overview page from
which you may navigate through the help system.
Please refer to the CST Studio Suite Getting Started manual to find more detailed explanations
about the usage of the CST MPhysics Studio Online Documentation.
57
Tutorials and Examples
The component library provides tutorials and examples, which are generally your first source of
information when trying to solve a particular problem. See also the explanation given when
following the Tutorials and Examples Overview link on the online help system’s start page.
We recommend that you browse through the list of all available tutorials and examples and
choose the one closest to your application.
Technical Support
Before contacting Technical Support, you should check the online help system. If this does not
help to solve your problem, you find additional information in the Knowledge Base and obtain
general product support at 3DS.com/Support.
Macro Language Documentation

More information concerning the built-in macro language for a particular module can be accessed
from within the online help system’s VBA book: Visual Basic (VBA) Language. The macro
language’s documentation consists of four parts:
 An overview and a general description of the macro language.

 A description of all specific macro language extensions.
 A syntax reference of the Visual Basic for Applications (VBA) compatible macro language.
 Some documented macro examples.

History of Changes
An overview of important changes in the latest version of the software can be obtained by
following the What’s New in this Version link on the help system’s main page or from the File:
Help backstage page. Since there are many new features in each new version, you should
browse through these lists even if you are already familiar with one of the previous releases.
58

CST Studio Suite - Thermal and Mechanical Simulation

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Thermal and Mechanical Simulation

3DS.COM/SIMULIA | © Dassault Systèmes | CST Studio Suite

Version 2020.0 - 8/16/2019

Information in this document is subject to change without notice. The software

No part of this documentation may be reproduced, stored in a retrieval

DS Offerings and services names may be trademarks or service marks of

3DS.COM/SIMULIA | © Dassault Systèmes | CST Studio Suite

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How to Get Started Quickly

1. Read the CST Studio Suite - Getting Started manual.

3DS.COM/SIMULIA | © Dassault Systèmes | CST Studio Suite

What is CST MPhysics Studio?

Who Uses CST MPhysics Studio?

3DS.COM/SIMULIA | © Dassault Systèmes | CST Studio Suite

Thermal Steady State Solver

Thermal Transient Solver

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Conjugate Heat Transfer Solver

SAM (System and Assembly Modeling)

 Display and integration of 2D and 3D fields along arbitrary curves

 Hierarchical result templates for automated extraction and visualization of arbitrary

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Simulation Workflow: Structural Mechanics

Create a New Project

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Define the Units

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Xmin -10 Xmax 6

5. Now click the OK button. A new brick has been created:

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Xmin 6.3 Xmax 7.5

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Xmin 7 Xmax 7.5

 Another one of Plastic with the following size:

Xmin -10 Xmax -9

Xmin -10 Xmax 7.5

 The result should be as shown in the following picture:

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Traction and Displacement Boundaries

1. Press the toolbar button Simulation: Boundaries  Displacement Boundary .

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Start the Simulation

Analyze the Solution of the Tetrahedral Solver

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Simulation Workflow: Coupled EM-CHT Simulation

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Background and Boundary Conditions

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