Multizone Meshing for a Tank Geometry with Piping

7-1ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

April 28, 2009Inventory #002645

Multizone Meshing for aTank Geometry with Piping

Workshop 7.2

Introduction to MultiZone Meshing



Training ManualGoals

• This tutorial will show how to use the Meshing Application in ANSYS 12 to generate a mesh suitable for a CFD simulation of a chemical process flow.

• The geometry, consists of three bodies representing a tank together with a single inlet and outlet pipe.

• The goal is to produce an Hex mesh throughout the domain without any further decompositionof the geometry using the Multizone Method.




Training ManualCreating a Standalone Meshing System

1. Launch ANSYS 12.0 Workbench from the START menu

2. Open the Component Systems section of the Toolbox on the LHS of the WB GUI.

3. Double click the Mesh option




Training ManualImporting the Geometry

4. Right click on the Geometry button in the RHS of the WB panel and select Import geometry (the question mark on the button turns to a tick once a geometry file is imported)

5. Import the 2-pipe-tank.agdb file

6. Double click on the Mesh button to launch the Meshing Application




Training ManualGeomety

7. The original geometry was modified in DesignModeler

• The tank was split into three bodies and some simplification was made to remove small faces that are not important to the analysis

• One multi-body “Part” was created and a given the name “Fluid” and the material type “Fluid”

• Individual bodies were re-named




Training Manual

8. In the Meshing Options panel to the RHS of the main window select the

following meshing options:

– Physics Preference

• CFD

– Mesh Method

• Automatic

– Click OK after you

made the selections

– In Units, make sure

it is set to Metric, 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 or set

your defaults from Tools>Options..>Meshing

Meshing Options




Training ManualNamed Selections

9. Named Selections are used to assign Fluent name and zone types

• Set the Cursor Mode to Face selection

• Select the inlet face

• RMB select Create Named Selection

• Assign the name Inlet

• Repeat for Outlet

• A naming convention has

been established to

automatically assign zone types in Fluent

• For example -

– “Inlet”

• Velocity-inlet zone

– “Outlet”

• Pressure-outlet zone

See Fluent Mesh export section

of the manual for all options.




Training ManualGlobal Mesh Settings

10. Set Global Size and Quality control

• Click on Mesh in the Model Tree to open up the Details of “Mesh” panel

• Sizing

– Turn Off Use Advanced Size Function• Multizone does not use this option

– Change the Relevance Center

• Fine

• Recommended for most CFD applications that apply the Multizone Method

• Statistics

– Assign Mesh Metric

• Option Skewness

• Maintain all other defaults




Training ManualInserting a Multizone Method

11. Insert Mutizone Meshing control

• Set the Cursor Mode to Body selection

• RMB (in Window) – Select All the bodies

• RMB (in Tree) – Insert – Method

• Select Multizone




Training ManualSetting Multizone Sources

12. Select Mutizone Source faces

• Change Src/Trg Selection – Manual Source

– To ensure the middle section can be swept

• Set the Cursor Mode to Face

• Pick the five green source faces(see top image)

• Rotate the model to look at therear of the tank

• Pick the additional fivered source faces(see bottom image)

• Apply




Training ManualGenerating the Initial Mesh

13. Create an initial Mesh of the model

• RMB (in Tree) – Generate Mesh

• The mesh is successfully created – but refinement is clearly needed

– The mesh at the inlet and outlet pipes and close to the pipe/tank intersection is insufficient to capture the physics correctly

– This can be achieved by inserting some additional meshing instructions such as Inflation, Sizing and Biased Sizing to improve the pipe/tank meshing




Training ManualFace Sizing

14. Add Face Sizing for the pipes to control the size of elements

• Start by removing the mesh

– RMB (in Tree) – Clean and confirm

• Make sure you’re using Face Selection and pick the four faces shown in Green

• RMB (in Tree) – Insert – Sizing

• Set Sizing Details: Set Element Size

– 1 mm




Training ManualAdding Inflation

15. Add Inflation(boundary layers)

• Set the Cursor Modeto Body Selection

• Select the centralgreen body

• RMB (in Tree) – Insert – Inflation

16. Set Inflation Details

• Switch to Face selection

• Select the four green cylindrical faces and Apply

• Set Inflation Control

– Number of Layers• 2

– Maximum thickness• 1 mm




Training ManualEdge Sizing

17. Add Edge Sizing

• Change Cursor Modeto Edge Selection

• Select two green edges on one side

• Rotate the model

• Repeat the selection

• RMB (in Tree) – Insert – Sizing

18. Set Sizing Details

• Element Size

– 1mm

• Behaviour

– Hard

• Bias type

– _ __ ___ __ _

• Bias Factor

– 6




Training ManualGenerating the Final Mesh

19. Generate the mesh

• RMB (in Tree) – Generate Mesh

• Statistics

– Elements

• ~45,000

– Max Skewness

• Below 0.8

• Overall a good Quality mesh




Training ManualExamining the Mesh

20. Examine the Mesh

Inflation –

on the pipe

walls

Sizing – 4

elements

on face

Sizing – element size 1mm

across pipe and biasing to

increase density at transition




Training ManualSaving the Project

21.The mesh is now complete

• RMB (Tree) select Update

• 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

22.Further Work

• Change the mesh settings for each of the additional parameters

– How do each of these parameters influence the mesh?

Documents

Multizone Meshing for a Tank Geometry with Piping