1. Chapter 7 Introduction to MultiZone Meshing
ANSYS Meshing Application Introduction

2. Overview Comparing Sweep and MultiZone
Comparing Thin Sweep and MultiZone
Example for Sweep, Thin Sweep, and Multizone Methods
Approach for the MultiZone Method
MultiZone Method Settings
Mapped Mesh Type
Free Mesh Type
Source Selection
Defeaturing
Inflation and MultiZone
Workshop 7.1 MultiZone Meshing for a Block Geometry with Pipes
Workshop 7.2 MultiZone Meshing for a Tank Geometry with Piping

3. Comparing the Sweep and MultiZone Methods
Some models can be meshed with either approach
Sweep Method:
Sweeps a single source/face to a single target/face.
Does a good job of handling multiple side faces along sweep
Geometry needs to be decomposed so that each sweep path is represented by 1 body.
MultiZone Method:
Free decomposition approach
Multiple sources to multiple targets

4. Sweep or MultiZone? Use Sweep Method when:
You have a multibody part where some bodies should be meshed with Sweep, and some with Patch Conforming Tet
If you want to use advanced size function
Preview Sweepable bodies shows that all bodies are sweepable
Use MultiZone when:
You are meshing single body parts that are too complicated for traditional sweep approach.
You have multiple sources and targets you need to respect (can’t use VTs to group into a single source/target)
You need to inflate off source and side faces

5. Comparing Thin Sweep and MultiZone
Thin Sweep Method:
Sweeps multiple sources to
paired multiple targets
Good substitute for midsurfacing shell models to get a pure hex mesh
MultiZone Method:
Free decomposition approach
Multiple sources to multiple targets
Some models can be meshed with either approach

6. Thin Sweep or MultiZone?
Use Thin Sweep Method when:
You have a “thin” solid part where the source and target faces don’t exactly match, and you don’t care about the features on the target side.
Use MultiZone When:
You have a “thin” solid part where the source and target faces don’t exactly match, and you care about the features on both sides.

7. Different Sweep Methods Example
Thin Sweep Method:
Sweep Method:
MultiZone Method:
For Example

8. Sweep Method Treatment
Use VTs to merge multiple sources into 1 source
Use VTs to merge multiple targets into 1 target
Multiple sources ignored
Multiple targets ignored

9. Thin Solid Sweep Treatment
Multiple source
Multiple target
Multiple sources captured
Multiple targets ignored

10. MultiZone Method Sweep treatment
Multiple source
Multiple target
Multiple sources captured
Multiple targets captured
Note, MultiZone will ignore the internal cutouts unless they are in a Named Selection

11. Multizone Method Approach
Multizone features automatic geometry decomposition which avoids the need to slice a body up into sweepable bodies to get a hex mesh with the sweep method
For example, the geometry shown at right would need to be sliced into three bodies to get a hex mesh with sweep. With the Multizone method, a hex mesh could be generated directly
Based on ICEM CFD Hexa blocking
O-grids can be extruded to create inflation
Unstructured regions can be filled with hex-dominant, hex-core, or tetrahedral mesh

12. Multizone Method Settings
Multizone will not utilize the Advanced Size Function (Patch Conforming Tet and Sweep Methods only)
Source selection is not mandatory, but may be helpful
Can exclude or allow free mesh blocks

13. Multizone Method Settings
Mapped Mesh Type
Hexa
Hexa/Prism
Free Mesh Type
Not Allowed
Tetra
Hexa Dominant
Hexa Core
Source/Target Selection
Automatic
Manual Source
Advanced
Defeaturing Tolerance
Minimum Edge length

14. Multizone Method and Inflation
Algorithm different from other inflation methods (extruded o-grid)
Scoped to bodies, defined for faces
Only First Layer or Total Thickness options

15. Workshop 7.1
Multizone Meshing for a Block Geometry with Pipes

16. Goals
This tutorial will illustrate basic use of the Multizone method to create a Hex mesh for a simple geometry with the addition of an inflation layer.
Source selection for the multizone sweep will be done automatically by the mesher when the mesh is generated. 16

17. Importing Geometry
Copy the blockandpipes.agdb file from the Tutorial Files folder to your working directory
Start Workbench and double-click the Mesh entry in the Component Systems panel
Right-click on Geometry in the Mesh entry in the Project Schematic and select Import Geometry/Browse
Browse to the block and pipes.agdb file you copied and click Open. Note that the Geometry entry in the Project Schematic now has a green check mark. 17

18. Insert Multizone Method
Double click the Mesh entry in the Mesh object on the Project Schematic to open ANSYS Meshing
Close the Meshing Options Panel at the right without setting anything.
Right-click on Mesh and insert a Method. Select the body and set the method to Multizone. Leave the settings as the defaults as shown

19. Mesh Sizing and Metric Click on Mesh in the Outline
Change the Physics Preference to CFD and the Solver Preference to Fluent
Expand the Sizing Entry and turn off the Advanced Size Function (it will not be used for Multizone anyway)
Set the Element Size to 0.20 [in]. (Note: if the units are set to some other system, click on Units in the Menu Bar and change to U.S. Customary (in, lbm, …)
Expand the Statistics entry and set the Mesh Metric to Skewness

20. Mesh and Mesh Quality
Generate the Mesh. Note the Mesh count and Skewness metric

21. Inflating the Multizone Method
Insert Inflation for the Multizone Method. Pick the outer cylindrical faces of the pipes and the 4 side faces of the block as the Boundary. Set the Inflation Option to Total Thickness with a value of 0.20 [in].
Generate the mesh.

22. Workshop 7.2
Multizone Meshing for a Tank Geometry with Piping

23. Goals
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 decomposition of the geometry using the Multizone Method. 23

24. Creating a Standalone Meshing System
Launch ANSYS 12.0 Workbench from the START menu
Open the Component Systems section of the Toolbox on the LHS of the WB GUI.
Double click the Mesh option
I’d like to remind everyone that some matters that will be discussed during this presentation may constitute forward-looking statements that involve risks and uncertainties, which could cause actual results to differ from those projected.
In addition, I would also like to mention that we will not be able to discuss or answer any questions regarding previously provided guidance, as our Company policy is that we only comment on company guidance in a public forum. 24

25. Importing the Geometry
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)
Import the 2-pipe-tank.agdb file
Double click on the Mesh button to launch the Meshing Application
I’d like to remind everyone that some matters that will be discussed during this presentation may constitute forward-looking statements that involve risks and uncertainties, which could cause actual results to differ from those projected.
In addition, I would also like to mention that we will not be able to discuss or answer any questions regarding previously provided guidance, as our Company policy is that we only comment on company guidance in a public forum. 25

26. Geomety 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
I’d like to remind everyone that some matters that will be discussed during this presentation may constitute forward-looking statements that involve risks and uncertainties, which could cause actual results to differ from those projected.
In addition, I would also like to mention that we will not be able to discuss or answer any questions regarding previously provided guidance, as our Company policy is that we only comment on company guidance in a public forum. 26

27. Meshing Options
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
I’d like to remind everyone that some matters that will be discussed during this presentation may constitute forward-looking statements that involve risks and uncertainties, which could cause actual results to differ from those projected.
In addition, I would also like to mention that we will not be able to discuss or answer any questions regarding previously provided guidance, as our Company policy is that we only comment on company guidance in a public forum. 27

28. Named Selections
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.
I’d like to remind everyone that some matters that will be discussed during this presentation may constitute forward-looking statements that involve risks and uncertainties, which could cause actual results to differ from those projected.
In addition, I would also like to mention that we will not be able to discuss or answer any questions regarding previously provided guidance, as our Company policy is that we only comment on company guidance in a public forum. 28

29. Global Mesh Settings 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 29

30. Inserting a Multizone Method
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 30

31. Setting Multizone Sources
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 the rear of the tank
Pick the additional five red source faces (see bottom image)
Apply 31

32. Generating the Initial Mesh
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 32

33. Face Sizing
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 33

34. Adding Inflation Add Inflation (boundary layers) Set Inflation Details
Set the Cursor Mode to Body Selection
Select the central green body
RMB (in Tree) – Insert – Inflation
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 34

35. Edge Sizing Add Edge Sizing Set Sizing Details
Change Cursor Mode to Edge Selection
Select two green edges on one side
Rotate the model
Repeat the selection
RMB (in Tree) – Insert – Sizing
Set Sizing Details
Element Size
1mm
Behaviour
Hard
Bias type
_ __ ___ __ _
Bias Factor 6 35

36. Generating the Final Mesh
Generate the mesh
RMB (in Tree) – Generate Mesh
Statistics
Elements
~45,000
Max Skewness
Below 0.8
Overall a good Quality mesh 36

37. Examining the Mesh Examine the Mesh Sizing – 4 elements on face
Inflation –
on the pipe walls
Sizing – element size 1mm across pipe and biasing to increase density at transition

38. Saving the Project The mesh is now complete Further Work
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
Further Work
Change the mesh settings for each of the additional parameters
How do each of these parameters influence the mesh?
I’d like to remind everyone that some matters that will be discussed during this presentation may constitute forward-looking statements that involve risks and uncertainties, which could cause actual results to differ from those projected.
In addition, I would also like to mention that we will not be able to discuss or answer any questions regarding previously provided guidance, as our Company policy is that we only comment on company guidance in a public forum. 38