Fluid and Structural Meshes for an Auto Manifold Workshop 5.2 ANSYS Meshing Application...

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April 28, 2009Inventory #002645

Fluid and Structural Meshes for an Auto Manifold

Workshop 5.2

ANSYS MeshingApplication Introduction

Tetrahedral Mesh with Inflation



Training ManualGoals

This workshop demonstrates the creation of a mesh suitable for a conjugate heat transfer (CHT) flow simulation, or a fluid-structure interaction (FSI) simulation. However, the geometry presents potential difficulties.

• The geometry contains two bodies. One

represents a solid manifold and the other

the fluid region.

• The mesh in the fluid body will be of CFD

quality, with inflation, whilst the solid mesh

will be of structural quality.

• The Patch Independent mesh method is

used to avoid problems arising from the

nature of the CAD (see later).

• This same geometry will later be meshed

using with the Patch Conforming Method

with Virtual Topology in Workshop A.1.




Training ManualOpen Workbench

1. Launch ANSYS 12.0 Workbench (WB) from the START menu

2. Click on Component Systems in the Toolbox on the LHS of the WB main panel

3. Double click the Mesh option




Training ManualGeometry Import

4. Right click on the Geometry button in the RHS of the WB panel and select Import geometry.

5. Import the Auto-manifold.agdb file

6. Double click on the Mesh button (in cell A3) to launch the Meshing Application




Training ManualGeometry Review7. The geometry was created by importing an IGES file for the manifold into DesignModeler and extracting the fluid region.

• On the right-hand-side of the screen, Select ‘Mechanical’ for the Physics

• Select ‘Automatic’ for the Meshing Method, then ‘OK’ that window.

• The units of the geometry should be set to mm.

*Note: If you are using ANSYS V14.0 or more recent versions of ANSYS then you will not see the Meshing Options panel at the

start of ANSYS Meshing. You will still be able to set the Physics Preference and insert any Mesh Methods manually.

8. Named Selections were created in DesignModeler. Expand the Named Selections object and click on each to see where they have been applied.

• If you cannot see the Named Selections in the Meshing Application, see next slide.




Training ManualNamed Selections

• If the Named Selections don’t appear in the Meshing Application, it is probably

because the option to bring them in is switched off.

• Activate the option by right clicking on the Geometry button on the Project Page,

and then select Properties.

• Ensure Named Selections is checked, and the Selection Key is blank.

• Right-Click on Geometry and select “Update”

• Right-Click on Mesh and select “Refresh”




Training ManualProblem Geometry

cusps

Short edge

Narrow

sliver faces

• The geometry includes many faces of various sizes and shapes and this would lead to problems for Patch Conforming methods. Virtual Topology could be an option to address this, but instead a Patch Independent approach will be used.




Training ManualSurface Meshes

refinement

small angles

• Patch Conforming Method

• Short edges – unwanted refinement and too many elements.

• Cusps and narrow faces –poor quality elements with small angles.

• Patch Independent Method

• Mesh not constrained by geometry.

• Coarser mesh possible.

• Elements are more regular in size and shape.




Training ManualInserting the Mesh Method

9. Left click on Mesh in the tree and check its details

• Make sure the Physics preference is set to Mechanical

– This ensures that the solid body will have a mesh suitable for

structural mechanics

10.Assign the Meshing method:

• Set the Cursor Mode to Body

• RMB (Window) select Select All

• RMB select Insert -> Method

– Depending on your Workbench settings,

sometimes a default Mesh Method is

already created for you. You can either

delete it and create the new one, or

modify its details as follows.

11.Set Details of Method

• Set the Method to Tetrahedrons

• Set Algorithm to Patch Independent

• Set Max Element Size to 10 mm

• Set Min Size Limit to 2.5 mm

Cursor Modes




Training ManualSetting Element Size for Fluid Region

12. Body Sizing

• Maintain the Cursor Mode of Body Selection

• Select the Fluid body

• RMB (Window) select Insert -> Sizing

13. Set Details of Body Sizing

• Set Element Size to 5 mm




Training ManualAdding a Boundary Layer Mesh to the Fluid

19. Insert Inflation

• Maintain the Cursor Mode of Body Selection

• Select the Solid Body

• RMB (Window) select Suppress Body

• RMB (Window) select Select All

• RMB (Window) select Insert Inflation

20. Set Details of Inflation

• Set the Cursor Mode to Face selection

• To select Inflation on all wall surfaces:

– Pick one face

– Drop down the Extend

menu and Extend to Limits

– Apply selection

• 126 Faces

• Change Inflation Option

– Total Thickness

• Set Maximum Thickness to 5 mm




Training ManualVolume Mesh Generation

21. Mesh the Bodies

• Set the Cursor Mode to Body selection

• RMB (in Window) select Unsuppress all Bodies

• RMB (in Tree) select Generate Mesh

• In Statistics set Mesh Metrics to Skewness

– Around 150 000 elements were created with a worst

skewness of about 0.9




Training ManualReview Volume Mesh

22. Review the Mesh

• Examine the surface mesh of the fluid region to see that it does not conform

to the underlying surface topology

– You can Hide the solid mesh region to make this easier by right clicking on it in

the geometry part of the Tree

• Try using a Section Plane ( ) to look at the interior of the mesh




Training ManualConclusion

23. The mesh is now complete

• RMB (Tree) select Update

– This ensures everything in the project so far is up to date

• Select File > Close Mesh to close the Mesh application

• In the WB panel select File > Save Project As… and give the project a name

• Exit from ANSYS Workbench by selecting File > Exit

• Note: Because the Mechanical mesh preference was used, the mesh

elements will contain midside nodes. This is a benefit for mechanical analysis

which can use higher order tetrahedral elements. If the mesh is then used for

CFD, these midside nodes will be automatically ignored.

Fluid and Structural Meshes for an Auto Manifold Workshop 5.2 ANSYS Meshing Application...

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