DesignModeler-Graphical User Interface

A. DesignModeler Overview

DesignModeler (DM) is a component of ANSYS Workbench.

A CAD-like modeler with analysis modeling goals:

Performs unique geometry modification capabilities for simulation:

-Feature Simplification

-Enclosure Operation

-Fill Operation

-Spot Welds

-Split Surfaces

-Surface Model Extraction

-Planar Body Extraction

-Beam Modeling

Contains parametric modeling capability:

-2D Sketcher with Dimensions and Constraints

Integrates directly with Ansys Workbench modules

-Simulation

-Meshing

-Advanced Meshing (ICEM)

-DesignXplorer

-BladeModeler

B. DesignModeler and CAD Files

A DesignModeler session can begin with CAD geometry:

File > Attach to Active CAD Geometry:

-Detects and imports current CAD model from open CAD system

-Plug-in mode (Bi-directional)

File > Import External Geometry File . . .

-Browse to and open neutral geometry files (Parasolid, SAT, etc.)

-Reader mode

Import options include:

Body type (solid, surface, all)

Simplification

-Geometry: turns NURBs into analytic geometry if possible

-Topology: merges duplicate entities

Clean/Heal: attempts to repair incomplete or poorly defined geometry

C. DesignModeler GUI Overview

GUI Layout:

-The menus and toolbars accept user input and commands

-Tool bars can be “docked” and re-sized to meet user’s preference

Two Basic Modes of Operation

-Sketching tab (2D)

-Modeling tab (3D)

D. Workbench Window Manager

Allows users to configure the individual panes as required

-Move and resize panes

-Tab Docking

-Auto Hiding

Auto Hiding

-Panes are either pinnedor unpinned

-An unpinned tab collapses when inactive

Moving and Docking

-Drag a title bar to move a pane (select with left mouse button and drag)

-Drag a tab to ‘undock’ a pane

-Use the docking targets to preview the resulting location of the pane

-Release the mouse button over a target to place or dock a pane

Restoring Original Layout

-Use “View>Windows>Reset Layout”

‘Window Management’ available in Simulation and Meshing

Efficient use of the workspace

Enables ease of use and intuitive operation

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DesignModeler-GUI Navigation

Goals:

-Start DesignModeler and open an existing database (agdb).

-Navigate through the GUI viewing controls.

-Create a new plane on an existing face of the model.

-Draw and dimension a 2-D sketch on the new plane (dimensioning will adequately specify the size and location of the sketch)

-Extrude the sketch to modify the existing geometry (cut a hole through the original part).

-Save the project and exit

Starting Workbench

-Start Workbench. Double click on Geometry under component systems.

-This will create a ‘Geometry component’ in the Project Schematic area.

Launching DM

-Right click onand select “Import Geometry >Browse”, and

select link1.agdb from the list

-Double click onand DesignModeler will be launched

Generate

Modeling and Sketching Modes

Tree Outline

Click the “+” next to “Extrude1” to expand the branch (if you have not done so yet).

-[Modeling]: Extrude1 > SKETCH1

-Observe that “SKETCH1” is associated with the XYPlane as well as Extrude1 in the tree outline

Mouse and Manipulation of Views

Click the blue “Iso” ball in the triad in the graphics window.

This orients the model to an isometric view.

Use the right mouse button and drag a zoom window around the top surface of the model. Note this is a shortcut for zoom operations (practice the use of mouse for graphics manipulation till you are familiar with the operations)

Generate a New Plane

Using the left mouse button click on the top surface to select it.

-Click on the “new plane” icon to create a plane. A preview of the plane is displayed with a triad at the plane origin (RGB = XYZ).

-Click on “Generate”.

Note: by pre-selecting the surface then creating the plane the details indicate the plane will be a “From Face” type.

Leave the default settings in the plane details and “Generate” the plane.

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Introduction to CFX-Transient Brake Rotor

Transient Brake Rotor

This case models the transient heating of a steel rear disk brake rotor on a car as it brakes from 60 to 0 mph in 3.6 seconds.

To keep solution times to a minimum the case has been simplified by removing the wheel and brake assembly to leave only the brake rotor. The brake pad is modeled by applying a heat source to a small region of the brake rotor.

Assumptions

-The ambient air temperature is 81 F and the rotor is at ambient temperature before braking begins

-The vehicle tire size is 205/55/R16

-The total vehicle weight including passengers and cargo is 1609 kg

-The entire kinetic energy of the vehicle is dissipated through the brake rotors

-Energy dissipation during braking is split 70/30 between the front and rear brakes and split evenly between the left and right sides

-The vehicles speed reduces linearly from 60 to 0 mph in 3.6 seconds

Solution Approach

-The solution is transient, so you will need to begin by solving a steady-state case at a vehicle speed of 60 mph

-You will need two domains; a solid domain for the brake rotor and a fluid domain for the surrounding air

-The reference frame will be that of the vehicle. So the rotor will be spinning relative to this reference frame and air will be flowing past at the vehicle velocity

Start Steady-State Simulation

1. Start CFX-Pre in a new working directory and create a new simulation named BrakeDisk
2. Right-click on Mesh in the Outline tree and import the CFX-Mesh file named BrakeRotor.gtm

-The rotor mesh will be imported along with a bounding box surrounding the rotor

1. In the Outline tree, expand Mesh > BrakeRotor.gtm > Principal 3D Regions

-There are two 3D regions in this mesh named B24 and B31

Examine Mesh Regions

1. Click once in the tree on each of these 3D regions

-The mesh bounding each 3D region is displayed in the Viewer

-Notice that a mesh exists for the solid brake rotor and for the surrounding fluid region. These meshes are in separate 3D regions but still within the same Assembly

Create the Fluid Domain

By default the Simulation Type is set to Steady-State, so the next step is to create the fluid domain

1. Select the Domain icon from the toolbarand enter the Name as AirDomain
2. Pick the Location corresponding to the air region from the drop-down menu

-The regions are highlighted in the Viewer to assist you

1. The fluid domain uses Air Ideal Gas as the working fluid at a Reference Pressure of 1 [atm]; the domain is Stationary relative to the chosen reference frame and Buoyancy (gravity) can be neglected. Use this information to set appropriate Basic Settings for this domain
2. Switch to the Fluid Models tab for the domain
3. Set the Heat Transfer Option to Thermal Energy and leave the Turbulence Option set to the default k-Epsilon model
4. Switch to the Initialisation tab for the domain

Create the Fluid Domain

1. Enable the Domain Initialisation, toggle

-All settings can then be left at their default values

1. Click OK to create the domain

Create the Solid Domain

The next step is to create the solid domain for the brake rotor.

1. Create a new domain named Rotor
2. Pick the Location corresponding to the brake rotor
3. Set the Domain Type to Solid Domain
4. Set the Material to Steel
5. Leave the Domain Motion Option as Stationary
6. Switch to the Solid Models tab and enable the Solid Motion toggle

Create Expressions

1. Set the Solid Motion Option to Rotating

The next quantity to enter is the Angular Velocity. This needs to be calculated based on the vehicle speed (60 mph) and the radius of the tire attached to the brake rotor. The tires were specified as 205/55/R16 (205 mm tire width, aspect ratio of 55, 16” rim diameter). Next you will create expressions to calculate the Angular Velocity.

1. Switch to the Outline tab (do not close the Domain tab)
2. Right-click on Expressions in the tree and select Insert > Expression

– You may need to expand the Expressions, Functions and Variables entry in the tree to be able to right-click on Expressions

1. Enter the expression Name as Speed and click OK

– The Expressions tab will appear

1. In the Definition window (bottom-left of the screen) enter
   60 [mile hr^-1] then click Apply

1. Right-click in the top half of the Expressions window and select Insert > Expression; enter the Name as TireRadius
2. Enter the Definition as (16 [in] / 2) + (205 [mm] * 0.55) and click Apply

14.Create another expression named Omega, type the Definition as Speed / TireRadius and then click Apply

15. Now switch back to the Domain: Rotor tab

Complete the Solid Domain

1. Click the expression icon next to the Angular Velocity field and type in Omega (the name of the expression you just created)
2. Pick the Rotation Axis as the Global X axis
3. On the Initialisation tab set the Temperature Option to Automatic with Value and enter a Temperature of 81 [ F ]

-Make sure you have changed the units to F

1. Now click OK to create the domain

Create Boundary Conditions

Boundary conditions are needed for the bounding box of the air domain. You will create an inlet boundary upstream of the rotor, an outlet boundary downstream of the rotor and an opening boundary for the remaining bounding surfaces. Start with the inlet boundary:

1. In the Outline tree, right-click on AirDomain and select Insert > Boundary. Enter the Name as AirIn when prompted and click OK
2. On the Basic Settings tab, set the Boundary Type to Inlet and the Location to Inlet
3. On the Boundary Details tab, set the Mass And Momentum Option to Normal Speed
4. In the Normal Speed field click the expression icon and enter Speed

-This is one of the expressions you created earlier

1. Set the Heat Transfer Option to Static Temperature and enter the a value of 81 [ F ]
2. Click OK to create the inlet boundary

Now create the outlet boundary condition:

1. Right-click on AirDomain and insert a boundary named AirOut
2. Use the following setting for this boundary:

-Boundary Type = Outlet

-Location = Outlet

-Mass And Momentum Option = Average Static Pressure

-Relative Pressure = 0 [ Pa ]

1. Click OK to create the outlet boundary

Lastly, create the opening boundary condition:

1. Insert a boundary named AirOpening into the AirDomain
2. Use the following settings for this boundary:

-Boundary Type = Opening

-Location = OuterWalls

-Mass And Momentum Option = Entrainment

-Relative Pressure = 0 [ Pa ]

-Turbulence Option = Zero Gradient

-Heat Transfer Option = Opening Temperature

-Opening Temperature = 81 [ F ]

1. Click OK to create the opening boundary

Create Domain Interface

Domain Interfaces are required when more than one domain exists in your simulation. Without domain interfaces one domain would not see or feel the effect of neighboring domains. A Default Fluid Solid Interface should already exist, but we will manually create the interface here as a practice exercise.

1. Select the Domain Interface icon from the toolbarand enter the Name as RotorInterface
2. Set the Interface Type to Fluid Solid
3. For Interface Side 1, set the Domain (Filter) to AirDomain; pick both BrakePadsFluidSide and RotorFluidSide from the Region List

1. For Interface Side 2, set the Domain (Filter) to Rotor. Pick BrakePadsSolidSide and RotorSolidSide from the Region List
2. Under Interface Models, leave the Frame Change and Pitch Change Option set to None

http://www.cadfamily.com/html/Article/Introduction%20to%20CFX-Transient%20Brake%20Rotor_783_1.htm

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CFX-Scripting and Batch Processing

Introduction

This workshop models flow over a backwards facing step with heat transfer through the lower wall. The quantities of interest are the Skin Friction Coefficient and the Stanton Number on the lower wall. The choice of turbulence model can influence these results, so you will use session files and scripts to run three simulations, each with a different turbulence model, and then compare the results.

Overview

In this workshop both the mesh and the physics definition are provided. The physics definition is contained in a CCL file that you will import into CFX-Pre to define the first simulation; you will then write a Definition file. The same Definition file will be used to run all three simulations, but additional CCL will be passed to the solver at run-time to alter the turbulence model.

You will write a short script to run all three simulations, providing the necessary solver arguments for each run.

Lastly you will create and edit a CFX-Post session file so that post-processing output can be created for all three simulations.

Define The First Simulation

1. Start CFX-Pre from the CFX Launcher (do not use Workbench for this example) and create a new simulation

-The first simulation will use the k-epsilon turbulence model

1. Import the mesh file backstep.gtm
2. Select File > Import > CCL
3. Import the file ke.ccl

The physics definition is imported. The CCL file you just imported was generated by setting up the simulation in CFX-Pre and then exporting the CCL through File > Export CCL.

Examining the Setup

Now take a minute to look at the simulation setup:

1D Interpolation Functions have been used to define Inlet velocity and turbulence profiles based on experimental data

The mesh is 1 element thick with symmetry boundaries on the X-Y planes

-This simplifies the simulation to 2D

There is a boundary named HeatedWall through which a constant Heat Flux is applied

The k-epsilon turbulence model is used

-The second and third simulations will use the SST and the k-omega turbulence models

Write the Solver File

You can now write the Definition file for the k-epsilon simulation.

1. Click the Write Solver File icon
2. Enter the filename as ke.def and click Save

Preparing CCL Files

The next step is to prepare CCL files that change the turbulence model and can be passed to the solver at run-time. You can use the existing CCL as a template. One way to extract the existing CCL is through the Command Editor in CFX-Pre.

1. Open a new text file in Notepad
2. In CFX-Pre, right-click on Default Domain in the Outline tree, and select Edit in Command Editor
3. Copy and paste all the text from the Command Editor to your text file

-Delete the lines Create Other Side = Off and Interface Boundary = Off under BOUNDARY: Default Domain Default and BOUNDARY: HeatedWall

-Save the text file in your working directory and name it SST.ccl

Now you can edit the text file in Notepad

1. Edit the TURBULENCE MODEL Option and the TURBULENT WALL FUNCTIONS Option located at the bottom of the file as shown:

1. Save the changes to SST.ccl

Now change to the k-omega turbulence model for the third simulation:

1. Edit the TURBULENCE MODEL Option as shown:

1. Save the file as komega.ccl

The files provided with this workshop contain a scripts directory which has copies of komega.ccl and SST.ccl. You can use these files if necessary. It is not recommended to copy and paste from Powerpoint because the formatting on some characters does not translate well to Notepad.

Create a Solver Script

The next step is to create a script that will run all the simulations in the solver. You could write the script in any scripting language that can be executed on your computer. Some options are Perl, a Windows batch script (.bat) or a UNIX shell script (.sh). In this workshop you will write a Perl script. This is a good choice because:

-Perl scripts can be run on Windows and UNIX/Linux platforms

-Perl comes built-in with your CFX installation and is integrated into CCL

-Perl is used elsewhere in CFX, so learning some basic Perl will allow you to add advanced features to CCL. You will see an example of this when post-processing this workshop.

1. Open a new text file in Notepad and save it in your working directory as runsolver.pl
2. Enter the following text (the file is also provided in the scripts directory with the workshop)

1. Save the changes to runsolver.pl

Notes on the Perl Script

The following provides a brief explanation of the syntax used in the Perl script:

-The first two lines provide information on how Perl should interpret the script. The details are not necessary here, but you can start all your Perl scripts with these two lines

-# is the comment character

-system executes the command in quotes

-Each statement should finish with the ; character

The Perl script runs the solver three times using different arguments each time. The first time the k-epsilon simulation is run by providing the Definition file to the solver. The second and third time the following additional arguments are provided:

–ccl <file>.ccl: this passes the CCL file to the solver that contains the new turbulence model settings. This CCL is processed after the CCL contained in the Definition file. In CCL, when the same parameter is defined more than once, the last CCL to be processed takes precedence

-ini <file>: uses the k-epsilon results to initialize the run

-name <name>: this sets the name of the .out and .res files output by the solver.

http://www.cadfamily.com/html/Article/CFX-Scripting%20and%20Batch%20Processing_784_1.htm

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Introduction to CFX-Tank Flushing

Introduction

This workshop models a water tank filling and then emptying through a siphon. The problem is transient in nature and solved as a two fluid multiphase case (air + water).

An initial water level is set in the tank. The water supply is turned on for the first second of the simulation and then shut off for the rest of the simulation. The water level rises until water flows out the U-tube generating a siphoning effect which effectively empties the tank.

Mesh Import

1. Start Workbench, add a CFX Component System, then edit the Setup to start CFX-Pre
2. Right-click on Mesh > Import Mesh >ICEM CFD
3. Set the Mesh Units to cm

-For some mesh formats it is important to know the units used to generate the mesh

1. Import the mesh flush.cfx5

Define Simulation Type

The first step is to change the Analysis Type to Transient:

1. Edit the Analysis Type object in the Outline tree
2. Set the Analysis Type Option to Transient
3. Set the Total Time to 2.5 [s]
4. Set the Timesteps to 0.01 [s] and click OK

-The simulation will have 250 timesteps

Edit Default Domain

1. Edit Default Domain from the Outline tree
2. Delete Fluid 1 under Fluid and Particle Definition
3. Click on the New icon
4. Name the new fluid Air
5. Set the Material to Air at 25C and the Morphology to Continuous Fluid
6. Create another fluid named Water
7. Set the Material to Water and the Morphology to Continuous Fluid

1. Turn on Buoyancy and set the (X, Y, Z) gravity components to (0, -g, 0)

-Use the expression icon to enter -g ( g is a built-in constant )

9 . Set the Buoy. Ref. Density to 1.185 [kg m^-3]

-This is the density of Air at 25 C. Search the help for “Buoyancy in Multiphase Flow” (including the quotes in the search) for more details

1. Switch to the Fluid Models tab
2. Under Multiphase Options, enable the Homogeneous Model

-This makes the simplifying assumption that both phases share the same velocity field

1. Set the Free Surface Model Option to Standard

-This changes some solver numerics to resolve the free surface interface better

1. Under Heat Transfer, enable the Homogeneous Model toggle and set the Option to None
2. Set the Turbulence Model Option to k-Epsilon

1. Switch to the Fluid Pair Model tab
2. Enable the Surface Tension Coefficient toggle and set the coefficient to 0.072 [N m^-1]
3. Under Surface Tension Force, set the Option to Continuum Surface Force
4. Set the Primary Fluid to Water
5. Under Interphase Transfer, set the Option to Free Surface
6. Click OK to complete the changes to the domain

Create Boundary Conditions

Start by creating an Opening boundary at the top of the tank to allow air to escape as the tank is filled:

1. Insert a new boundary named Ambient
2. Set the Boundary Type to Opening and the Location to AMBIENT
3. On the Boundary Details tab, set the Mass and Momentum Option to Opening Pres. And Dirn with a Relative Pressure of 0 [Pa]
4. On the Fluid Values tab, set the Volume Fraction of Air to 1 and the Volume Fraction of Water to 0
5. Click Ok to create the boundary

http://www.cadfamily.com/html/Article/Introduction%20to%20CFX-Tank%20Flushing_782_1.htm

Electronics Cooling with Natural Convection and Radiation

Goals

This workshop models the heat dissipation from a hot electronics component fitted to a printed circuit board (PCB) via a finned heat sink. The PCB is fitted into a casing, which is open at the top and bottom.

Initially only the heat transfer via convection and conduction will be modelled. The effect of thermal radiation will then be included at a later stage.

Loading Mesh (Workbench)

1. Open a new Workbench project and save it as HeatSink.wbpj
2. Look in the Component Systems section of the toolbox and drag a CFX system onto the Project Schematic
3. Double-click Setup to start CFX-Pre

1. In CFX-Pre, right-click Mesh and select Import Mesh > ANSYS Meshing
2. Select HeatSink.cmdb and click Open

Options

1. In the tree expand Case Options, double-click General and ensure that Automatic Default Domains is switched on and Automatic Default Interfaces is active.
2. Set the Interface Method to One Per Domain Pair. Click OK.

Create Fluid Domains

First add a domain for the fluid region. The effects of buoyancy must be included, as the flow is driven by natural convection. The buoyancy reference density represents the density at the ambient conditions.

1. Right-click on Flow Analysis 1 and insert a new domain named Fluid
2. Open the details for Fluid and set the Location to Fluid
3. Set the Material to Air Ideal Gas
4. Switch the Buoyancy option to Buoyant and set the directional components to (0, -g, 0)

– Click on the expression button to enter –g

1. Set the Reference Density to 1.1093 [kg m^-3]
2. Click the Fluid Models tab
3. Set Heat Transfer to Thermal Energy and Turbulence to None (Laminar)
4. Click OK

Creating Materials

CFX contains a library of many materials, but for this case we will create user materials for the component and Printed Circuit Board (PCB).

1. In the tree right-click on Materials and select Insert > Material. Name it ComponentMat
2. Define the material as a Pure Substance in the CHT Solids Material Group
3. Enable Thermodynamic State and select Solid

– This must be set to allow it to be used in a solid domain

1. Click the Material Properties tab and set Density to 1120 [kg m^-3]
2. Select Specific Heat Capacity and set it to 1400 [J kg^-1 K^-1]
3. Expand Transport Properties and set Thermal Conductivity to 10 [W m^-1 K^-1]
4. Select OK

1. Repeat steps 1-7 to create PCBMat using

– Density = 1250 [kg m^-3]

– Specific Heat Capacity = 1300 [J kg^-1 K^-1]

– Thermal Conductivity = 0.35 [W m^-1 K^-1]

Create Solid Domains

This case contains three different solid parts that use different materials. Each part will be created as a different domain.

1. Insert a new domain called HeatSink
2. Set the Location to HeatSink
3. Set the Domain Type to Solid Domain with the Material set to Aluminium
4. Click OK to create the domain

– Note that an interface between the two domains is automatically created

1. Repeat steps 1-4 to create a solid domain called Component located at IC using the Material ComponentMat, and a further solid domain called PCB located at PCB using PCBMat

Adding Energy Source

The component is generating 75 [W] of heat which must be added to the simulation. To add this energy source in CFX, a subdomain must be created.

1.In the tree right-click on the Component domain and select Insert > Subdomain, using the name Chip

2.Set the Location to IC so the subdomain occupies the whole of the Component domain

3.Switch to the Sources tab and check the Sources box and the Energy box

4.Set the Option to Total Source, enter75 [kg m^2 s^-3] then click OK

Boundary Conditions

For this case all of the heat will be extracted by the air passing over the heat exchanger so all solid walls will be defined using adiabatic settings. Within the simulation heat can pass between all of the solid and fluid domains because interfaces have been automatically created.

To allow air to enter or leave the simulation domain, the top and bottom face of the fluid domain are defined as openings.

1. Right-click on the Fluid domain and insert a new boundary called Walls and set the Boundary Type to Wall
2. Set the Location to Wall
3. Switch to the Boundary Details tab and check that Heat Transfer is set to Adiabatic then click OK
4. In the PCB domain rename PCB Default to PCBwalls and check that Heat Transfer is set to Adiabatic

1. In the Fluid domain rename Fluid Default to Openings and check that the Location is set to be the two ends of the fluid domain
2. In the Basic Settings tab change the Boundary Type to Opening
3. In the Boundary Details tab set the Mass and Momentum option to Opening Pres. and Dirn with a relative pressure of 0 [Pa]
4. Set Heat Transfer to Opening Temperature at 45 [C]

Solver Control

1. From the tree right-click Solver Control and select Edit
2. Increase the Max. Iterations to 500
3. Leave the Fluid Timescale Control set to Auto Timescale
4. Leave Solid Timescale set to Auto Timescale

-Note that solid regions will use a much larger timescale than fluid regions because only the energy equation is being calculated within the solid

1. Click OK

http://www.cadfamily.com/html/Article/Electronics%20Cooling%20with%20Natural%20Convection%20and%20Radiation_781_1.htm

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