AIM R16 WS02 Rear Spoiler

7/23/2019 AIM R16 WS02 Rear Spoiler

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Chapter 2: Rear Spoiler

This tutorial demonstrates how to perform a fluid analysis using ANSYS AIM.

In this tutorial you will learn how to

Launch ANSYS AIM.

Import the geometry.

Create a computational mesh.

Set up the simulation which includes setting the material properties and boundary conditions.

Calculate a solution.

Examine the results.

2.1. Prerequisites

This tutorial assumes that you have limited experience with ANSYS AIM so each step will be explicitly

described.

2.2. Problem Description

The goals are to demonstrate the ability of ANSYS AIM to import a CAD model, perform a fluid analysis,

and evaluate design changes using the Workbench Parameter Manager.

You will import a CAD model of a rear spoiler, mesh it, define materials, and solve a fluid analysis. You

will then use the Parameter Manager to evaluate how changing the angle of the spoiler will affect the

air flow.

2.3. Setup And Solution

The following sections describe the setup and solution steps for this tutorial:

2.3.1. Preparation

2.3.2. Starting AIM

2.3.3. Geometry

2.3.4. Mesh

2.3.5. Physics

2.3.6. Results

2.3.1. Preparation

1. Create a working folder on your computer.

1Release 16.0 - SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationof ANSYS, Inc. and its subsidiaries and affiliates.


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2. Copy the file Rear_Spoiler.agdbto the working folder.

Note

Clean up the geometry before using it.

2.3.2. Starting AIM

In this step you will start ANSYS AIM and set up a simulation process.

1. From the Windows Startmenu, select Start > All Programs > ANSYS 16.0 > ANSYS AIM 16.0to start a

new ANSYS AIM session.

The ANSYS AIM application window will appear. The various Simulation Process Templatesare

displayed in the Studypanel at the left. The Helpwindow is displayed on the right-hand side. It

contains links to instructional videos and the Helpmenu. The Workflow tab is displayed at the

bottom.

2. Click on the Projecttab to go to the Workbench window.

You can see that a Study Component System is present in the Project Schematicwindow.

3. Drag the Geometry Component Systemon to the Project Schematic.

4. Double click on the Geometrycell (cell 2) to open DesignModeler.

a. In DesignModeler load the geometry file (Rear_Spoiler.agdb).

File> Load DesignModeler Database...

Release 16.0 - SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationof ANSYS, Inc. and its subsidiaries and affiliates.2

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You can see in the Tree Outline that one of the Body Transformation operation, Rotate is

parameterized.

b. Close DesignModeler.

You can see in the Project Schematic that a Parameter Sethas been added.

5. You will use this geometry as an input for AIM. Drag the Geometrycell (2) to the Studycell (2). A connec-

tion is formed.


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2.3.3. Geometry

1. Click the Studytab to return to the ANSYS AIM workspace.

Right-click on the Importcell in the Workflowtab, and select Update. The fluid volume from Design-

Modeler is imported in ANSYS AIM and displayed in the graphics area.

2. Save the project Rear_Spoiler.

Home( ) > File> Save

2.3.4. Mesh

1. Now you need to mesh the geometry.You can do this by either:


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Clicking on Geometry> Add Next> Meshingin the Workflowtab.

Clicking on Add > Meshingin the Geometrypanel under Connected Tasks.

RMB in the graphics window and clicking on Add Next Task> Meshing.


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2. The Meshpanel indicates the Attention requiredstatus.

3. Select Fluid flowfrom the Engineering intentdrop-down list.

4. Move the slider bar for Mesh resolutiontowards Highas shown in Figure 2.1: Mesh Panel (p. 6).

This will result in a better mesh.

Figure 2.1: Mesh Panel


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5. Under Common Inflation Settingsselect Layer compressionfrom the list of Collision avoidance.

Note

Stair stepping which was selected by default will create some pyramid elements and

you would like to prevent pyramid elements.

6. Click on Addnext to Mesh Controlsunder Objects. Select Inflationfrom the drop-down list.

Note

Inflation is to get a resolution of the boundary layer. In fluid dynamics you need to resolve

the boundary layer.

a. Right-click in the graphics window, and click on Select All. This will select all the faces of the fluid

volume and geometry. Now deselect the faces of the cuboid volume by holding down the control

(Ctrl) key.

Note

Inflation will be on the mounting foot of the support plate. This is done to prevent

stair stepping.

b. Click on the + sign next to the Locationtext box.

c. Select Last aspect ratiofrom the Inflation optiondrop-down list.

d. Enter 5e-04m for First layer height.

e. Enter 5for Maximum layers.

7. Return to Meshin the navigation bar.You can see that it is Out-of-datenow since the sizing is changed.

8. Generate the mesh by clicking on the Generate Meshbutton (with a lightning bolt) in the panel (top and

next to Output), or Workflowtab or you can right-click and select Generate Meshfrom the context

menu.


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Figure 2.2: Mesh

As you see the mesh has inflation layers and is reasonably good.

9. Click on Statisticsunder Output.You can see that the Number of nodesis about 2.05 E+05and the

Number of elementsis about 8.58E+05. A mesh of this size is appropriate for a tutorial to give good

results. You might want to have a finer resolution mesh in reality.

2.3.5. Physics

Add a Physicstask. You can do this by either:

Clicking on Mesh> Add Next> Physics Solution in the Workflowtab.

Clicking on Add>Physics Solutionin the Meshpanel under Connected Tasks.

RMB in the graphics window and selecting Add Next Task > Physics Solution.

In the Physicspanel you will start by defining the Physics Region.


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1. Click on Physics Region.

a. Enable Fluid flowin the list of Physics types.

b. Enable Body selection( ). Click on the volume in the graphics area and then click on the + sign

next to Locationtext box in the Physics Regionpanel. This selects the whole volume.

c. Click Apply.

2. Return to Physicspanel. Click on Addbutton next to Material Assignmentsunder Objects, and click

on New usingfrom the list.

Note

Material is important because some of the default settings will depend on the materialselection. If it is compressible or incompressible or structural or fluid or solid.


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a. Select Air. This opens the Air Assignmentpanel.

b. Enable Body selection( ) and select the volume in the graphics area and then click on the + sign

next to Locationtext box.This selects the whole volume.

3. Return to Physicspanel. Now you will add boundary conditions. To add boundary condition click on Add

next to Boundary Conditionsand select Inletfrom the list.

a. Enable Face Selection ( ) and select the face of the volume as shown Figure 2.3: Face Selected

for Inlet Boundary Condition (p. 11).


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Figure 2.3: Face Selected for Inlet Boundary Condition

b. Right-click in the graphics window. Select Add> Boundary Conditions> Inletfrom the context

menu.

c. The Flow specificationis set to Velocityby default. Retain the selection.


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d. Enter 80m s^1 for Magnitude.This is the speed of the air at the inlet.

e. Retain Normal to boundaryselection for Direction.

4. Add another boundary condition. Select the opposite face as shown.


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Figure 2.4: Face Selected for Outlet Boundary Condition

a. Right-click in the graphics window. Select Add> Boundary Conditions> Outletfrom the context

menu.

b. The Flow specificationis set to Pressureby default. Retain the selection.


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c. Enter 0Pa for Gauge static pressure. (The gauge pressure is set to 1 atmosphere).

d. Retain the other default settings.

5. Select the three remaining faces of the cuboid except the symmetry plane as shown in Figure 2.5: Faces

Selected for Opening Boundary Condition (p. 15).


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Figure 2.5: Faces Selected for Opening Boundary Condition

a. Right-click in the graphics window. Select Add> Boundary Conditions> Openingfrom the context

menu.

Here the air is allowed to flow in and out.

b. The Flow specificationis set to Pressureby default. Retain the selection.

c. Enter 0Pa for Gauge entrainment pressure. (The gauge pressure is set to 1 atmosphere).

d. Retain the other default settings.

6. Now select the face which includes the spoiler face as shown in Figure 2.6: Symmetry Faces Selection (p. 16)


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Figure 2.6: Symmetry Faces Selection

Right-click in the graphics window. Select Add> Boundary Conditions> Symmetryfrom the context

menu.

7. Now you need to set the base of the spoiler as a wall. Select the face on the base as shown in Fig-

ure 2.7: Mounting Face of the Spoiler (p. 16).

This is the mounting foot of the spoiler unit.

Figure 2.7: Mounting Face of the Spoiler


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a. Right-click in the graphics window. Select Add> Boundary Conditions> Wallfrom the context

menu.

b. Select Free slipfrom the Flow specificationdrop-down list.

This is not a friction wall. In practical conditions this base will be mounted on the car.

8. Return to the Physicspanel.

a. Click on Addnext to Boundary Conditionsand select Wall from the list that appears. Now all the

remaining elements the geometry which are not defined, will be defined as wall.

b. Retain the default selection of No slipfrom the Optiondrop-down list under Flow Specification.

9. Return to Physicspanel. Retain the default options under Solver Options.

Now you are ready to solve.

10. The Physicstask is now ready to be updated.You can update it by either clicking blue lightning bolt next

to the Out-of-datemessage near the top of the Physicspanel, the blue lightning bolt next to the Output

tab near the bottom of the Physicspanel, by selecting Updateunder the Workflowtab, or by RMB

within the graphics window and selecting Solve Physicsfrom the context menu.

You can see the status in the progress bar. In the Workflow tab you can also review the progress

using the Transcripttab.


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In the transcript you can see:

Number of CPU used for solving

A list of all the boundary conditions

Partitioning factors

Initialization values set by default

Iterations solved and the residuals of continuity, momentum equations, turbulent kinetic energy,

and turbulent frequency.

You can also check the Solution Quality tab which shows the convergence plot.

11. When solving is finished the Physicspanel shows the Up-to-datestatus.

12. Periodically save the project.


2.3.6. Results

Add a Resultstask. You can do this by either:

Clicking on Physicscell > Add Next> Results Evaluationin the Workflowtab.

Clicking on Add>Results Evaluationin the Physicspanel under Connected Tasks.

RMB in the graphics window and selecting Add Next Task> Results Evaluation.

1. In the Resultspanel click Addnext to Resultsand select Contourfrom the drop-down list.

a. Select Symmetry 1from the Locationdrop-down list.

b. Select Pressurefrom the Variabledrop-down list.

c. Click Evaluate. See Figure 2.8: Pressure Contours (p. 19).


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Figure 2.8: Pressure Contours

You can hide the other faces to get a better view. To hide a face first ensure that Face Selection

( ) is enabled. Then select the face, RMB and select Hide Facefrom the context menu. To

see the influence of the support unit, define a plane parallel to the symmetry plane which

goes midway through the spoiler. This will give an undisturbed pressure contour at the wings.

d. Click on the Y-Axis of the coordinate system to align the view towards this coordinate system.

2. Return to Resultspanel. Click Addnext to Construction Geometryand select Planefrom the list.

a. In the Planepanel retain the selection of Origin and orientationfor Construction method.

b. Click on the >button next to Origin and Orientation Definition. In the list that opens up click on

Axis 1> Direction> Vector> Cartesian

c. Enter 1,0,0for X,Y, and Zrespectively under Cartesian.


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d. Click on the >button next to Transformation. In the list that opens up click on Offset.

e. Retain the selection of Magnitude and directionfor Define by.

f. Enter -0.35m for Magnitude.

g. Click on the >button next to Direction.

h. Retain the selection of Cartesianfor Coordinate type.

i. Click on the >button next to Cartesian.

j. Enter 0,0,1for X,Y, and Zrespectively under Cartesian.

3. Now you will add a velocity magnitude contour on the plane you just created. Return to Resultspanel.

In the Resultspanel click Addnext to Resultsand select Contourfrom the drop-down list.

a. Select Plane 1from the Locationdrop-down list.

b. Select Velocity Magnitudefrom the Variabledrop-down list.

c. Click Evaluate. See Figure 2.9:Velocity Magnitude Contours on Plane (p. 21).


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Figure 2.9: Velocity Magnitude Contours on Plane

4. Return to Resultspanel. Click Addnext to Resultsand select Isosurfacefrom the list.

a. Select Q Criterionfrom the Velocitydrop-down list in the Isosurfacepanel.

b. Click on the >button next to Isovalues.

c. Select Set valuesfrom the Isovalue specificationdrop-down list.

d. Enter 0.01for Isovalues.

e. Click Evaluate. See Figure 2.10: Q Criterion Iso Surface (p. 22).


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Figure 2.10: Q Criterion Iso Surface

5. Return to Resultspanel. Click Addnext to Resultsand select Streamlinefrom the list.


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a. Select Wall 2from the Seed locationdrop-down list in the Streamline 1panel.

b. Retain Uniformly distributedfrom the Distributiondrop-down list.

c. Enter 300for Approximate number of points.

d. Retain Forwardfrom the Directiondrop-down list.

e. Click Evaluate.

6. Return to Resultspanel. Click Addnext to Resultsand select Contourfrom the list.You can use the

streamline created to color the streamlines by velocity.

a. Select Streamlinefrom the Locationdrop-down list.


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b. Select Velocity Magnitudefrom the Variabledrop-down list.

c. Click Evaluate. See Figure 2.11: Streamlines Colored by Velocity (p.24).

Figure 2.11: Streamlines Colored by Velocity

7. Return to Resultspanel. Click Addnext to Resultsand select Calculated Valuefrom the list.

a. Rename the panel to DownForce.

b. Select Wall 2from the Locationdrop-down list.

c. Select Sumfrom the Functiondrop-down list.

d. Select Simplefrom the Weight typedrop-down list.

e. Select Force Zunder Force/Momentfrom the Variabledrop-down list.


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f. Click Evaluate.

g. Click on the triangular button next to the resultant Valueand click on Create named expression /

value( ) button.

h. Enter DownForcefor Referenced by name.

i. Click Create.

j. Click on the triangular button next to the resultant Valueand click on Parametrizebutton.

8. Return to Resultspanel. Click Addnext to Resultsand select Calculated Valuefrom the list.

a. Rename the panel to DragForce.

b. Select Wall 2from the Locationdrop-down list.


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c. Select Sumfrom the Functiondrop-down list.

d. Select Simplefrom the Weight typedrop-down list.

e. Select Force Yunder Force/Momentfrom the Variabledrop-down list.

f. Click Evaluate.

g. Click on the triangular button next to the resultant Valueand click on Create named expression /

value( ) button.

h. Enter DragForcefor Referenced by name.

i. Click Create.

j. Click on the triangular button next to the resultant Valueand click on Parametrizebutton.

9. Now you will be creating a named expression for the pressure coefficient. Click on the >button next to

Studyin the navigation bar and select Named Expressions / Valuesfrom the drop-down list.

a. In the Named Expressions / Valuespanel click on Named Expressionfrom the drop-down list of

Add Named Expression.

b. Rename the Named Expressionpanel as PressureCoefficient.


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c. Enter Pressure/(0.5*Density*(80[m/s])**2)for Expression.

Note

Definition of Pressure is (Absolute Pressure Reference Pressure). Pressure coeffi-

cient is this pressure value divided by half of density times the reference velocity

squared.

10. Return to Resultspanel. Click Addnext to Resultsand select Contourfrom the list.

a. Select Wall 2from the Locationdrop-down list.

b. Select PressureCoefficientunder Expressionfrom the Variabledrop-down list.

c. Click Evaluate. See Figure 2.12: Pressure Coefficient under the Wings (p. 28).


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Figure 2.12: Pressure Coefficient under the Wings

11. Now you will be creating a named expression for the ratio of down force and drag force. Click on the >

button next to Studyin the navigation bar and select Named Expressions / Valuesfrom the drop-down

list.

a. In the Named Expressions / Valuespanel click on Named Expressionfrom the drop-down list of

Add Named Expression.

b. Rename the Named Expressionpanel as DownForce_2_Drag_Ratio.

c. Enter -DownForce/DragForcefor Expression.


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Note

Since down force is a negative value you have added a minus sign to the expression.

12. Periodically save the project.


13. Now return to the Workbench Project Schematicby clicking on the Projecttab.You can see that the

Parameter Setis now in a closed loop. Double click on the Parameter Setto access Parameter Manager.

a. In the Outline of Parameterspanel, you can now see one Input Parameterand two Output Para-

meters(DownForce and DragForce), are defined.


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b. In the Table of Design Pointsyou can see all these in a row. Right click on row DP 0 (Current)and

select Duplicate Design Pointfrom the context menu. Do this one more time.

c. Set P1 AoA_Rear_Wingto 0.017and -0.017for DP 1and DP 2respectively.

Note

0.017 radian is approximately equal to 1 degree. So you will be checking how a

change in one degree of the angle of the rear wing on either side affects the drag

and down force. You can add design points of your choice to check the results.

d. Click on Update All Design Points.

2.4. Summary

With ANSYS AIM interface you can perform a static structural analysis. You learned how to:

1. Set-up a structural analysis in AIM using a template,

2. Import CAD geometry with parameters,

3. Create and modify a mesh,

4. Assign materials from existing libraries,

5. Create and assign new materials,

6. Apply boundary conditions,

7. Solve the analysis,

8. Post-process results, and

9. Assess design changes using design points in the Workbench Parameter Manager.

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