1. Section 7 Mesh Control

2. Mesh Control Overview
The automated meshing process in SimLab can generate mesh that is suitable for the following Analysis Types.
Analysis type
Durability / Stress analysis
NVH analysis
Acoustic analysis
Drop test
Fluid analysis
For each of the above analysis types, the desired mesh density and the quality of the mesh differs. In SimLab, the output mesh is controlled by specifying Mesh Controls.
Mesh controls are applied directly to the CAD models.

3. Mesh Control - Classifications
Mesh controls are classified under the following types,
Global mesh controls
It is assigned to bodies or assemblies and all underlying geometry entities, (faces and edges), will inherit this global mesh control.
It is mandatory to specify the global mesh control.
Local mesh controls
Local mesh controls are used to control the mesh in a particular region.
It over rides the global mesh controls.
It is assigned to bodies, faces and edges.

4. Global Mesh Controls
Global mesh controls are defined while surface meshing or volume meshing.
Surface meshing
Surface meshing is used to generate a surface mesh body from a CAD body.
Surface elements supported are Tri3, Tri, Quad4, Bar2 and Bar3.
Volume meshing
Volume meshing is used to generate a volume mesh body from a CAD body or a surface mesh body.
Volume elements supported are Tet4, Tet10, Wedge6 and Hex8.

5. Global Mesh Controls
Surface meshing

6. Global Mesh Controls
Volume meshing
Input

7. Global Mesh Controls
Volume meshing
Output

8. Local Mesh Controls The local mesh controls available are
Mesh size on geometry
Body
Faces
Edges
Regions (with Break option)
Mesh size on features
Fillets
Cylinders
Washer
Circle Imprint
Valve Seat Pocket
Iso-Line
Seeding
Hard points
Faces
Edges
Preserve Entities
Face Edges
Face shape
Edge
Mesh
Symmetry Mesh
Mesh Patterns
Isomesh
Free Mesh
Union Jack

9. Local Mesh Controls Following are the local mesh control parameters,
Face Mesh Control
Edge Mesh Control
Body Mesh Control
Fillet Mesh Control
Cylinder Mesh Control
Washer Mesh Control
Circle Imprint Mesh Control
Region Mesh Control
Valve Seat Pocket Mesh Control
Iso-Line Mesh Control
Volume Layer Mesh Control

10. 1. Face Mesh Control
Face Mesh Control is used to control the mesh on the selected local faces. A uniform mesh is generated on the face that has the face mesh control specified.
Input
Output Mesh

11. 2. Edge Mesh Control
Edge seeds are applied either by specifying average element size or number of elements.
Bias Seeding is used to seed an edge such that a constant ratio is maintained between adjacent bar elements. Edge Length will be in the following series:
Lmin, Lmin * r, Lmin * r * r, . . .
where, Lmin is the minimum edge length and r is the ratio.
Input
Output Mesh

12. 3. Body Mesh Control
Body Mesh Control is used to control the mesh on selected local bodies.
All entities (faces and edges) present in the body, except the entities with other local mesh controls, will inherit this mesh control.
Input
Output Mesh

13. 4. Fillet Mesh Control
Fillet Mesh Control is used to control the mesh over fillets along the length and the curve direction.
Input
Output Mesh

14. 5. Cylinder Mesh Control
Cylinder Mesh Control is used to control the mesh both axially and radially on the selected cylindrical faces.
Input
Output Mesh

15. 6. Washer Mesh Control
Washer mesh control is used to create rings around a circle.
The circle has to be inside one face.
Input
Output Mesh

16. 7. Circle Imprint Mesh Control
Creates circular edge on a face with the specified radius and the number of seeds.
Input
Output Mesh

17. 8. Region Mesh Control
Region mesh control applies local refinement within the defined shape (Cuboid / Cylinder) of region.
The selected entities (faces/bodies) that lies inside the region will be assigned the specified size.
Entities which are partially inside the region will be graded according to region of overlap.
Also the region can break the face/body along the boundary of the chosen shape (Cuboid / Cylinder / Plane).
The Plane option is used to Break the body or face.

18. 8. Region Mesh Control
Region Mesh Control -Cylinder – Local Size – Without Break
Input

19. 8. Region Mesh Control
Region Mesh Control -Cylinder – Local Size – Without Break
Output

20. 9. Valve Seat Mesh Control
Valve Seat Mesh control is used to control the mesh in the valve seat pocket region. This controls the mesh on the cylinder and disc faces in the axial and radial direction and also preserves the chamfer faces if needed.

21. 9. Valve Seat Mesh Control
Valve Seat Mesh control without Preserve Chamfer
Input
Output

22. 9. Valve Seat Mesh Control
Valve Seat Mesh control with Preserve Chamfer
Input
Output

23. 10. Iso Line Mesh Control
Iso-Line Mesh control is used to control the mesh on cylinders and partial cylinders.
It strictly maintains the axial mesh size and the angle.
This separates iso-line mesh control from fillet and cylinder mesh controls.
Reference point and direction is used to define the start point and the direction of the isomesh.
Merge option is used to merge the selected faces.
Reference point is also used to generate a mesh such that a radial shift of the iso- mesh is required.

24. 10. Iso Line Mesh Control
Input
Output

25. 11. Volume Layer Mesh Control
Volume Layer Mesh control is used to generate layers of Tet elements along thin regions.
The number of layers can also be specified in terms of the thickness of each layers. This option is useful when the number of layers have to change with the thickness for a body that has regions of variable thickness.

26. 11. Volume Layer Mesh Control
Input

27. 11. Volume Layer Mesh Control
Output

28. Hard Points – Mesh Control
Hard points are used to create nodes at the specified point location on a face or an edge during meshing.
Hard Points can be defined by selecting a point on the face/edges. In case of meshed body we can select nodes as hard point.
Input
Output Mesh

29. Preserve Entities
The automated meshing process can collapse sliver faces. The mesher will automatically decide which one to preserve and which one to collapse.
Using Preserve Entities mesh control, the user can control the features to be preserved while meshing.
There are five types of preserve entities.
Face Shape
Face Edges
Edge
Symmetry Mesh
Mesh

30. Preserve Entities Face Shape
This option is used to retain the planarity of the face after meshing. The nodes in the face will not get moved out of the face.
Face Edges
This option is used to retain all the edges of the face after meshing. This means that tiny edges on the faces will be preserved and the face will not get collapsed.
Edge
This option is used when only few edges of a face, are to be preserved when meshing.

31. Preserve Entities Symmetry Mesh
This option is used to get identical mesh between the master face and symmetry face.
If there are any discontinuous edges, then we need to pick three nodes/vertices in an order for both master and symmetry face.
Mesh
This option is used to maintain the existing mesh in the face during meshing.

32. Mesh Patterns Mesh Pattern
The manner in which elements are arranged in a face is known as mesh pattern. The three types of mesh pattern available are,
Iso-Mesh
This create elements that have 2 edges almost 90 degrees and the diagonals are inclined in the same direction. This iso-mesh pattern can be created on a four sided surfaces.
UnionJack
This create elements that have two edges almost 90 degrees and the diagonals are inclined in the opposite direction.
Free Mesh
This creates a mesh wherein, the mesh does not follow any pattern.

33. Mesh Patterns

34. Local Mesh Controls Local mesh controls
Select “Mesh Control” in meshing tool bar.
This opens the “Mesh Control Parameters” dialog box.
Select entities and enter values for the mesh control.
Created “Mesh controls” are listed in the “Assembly Model” tree window under “Process Control” tab.

35. Modifying Local Mesh Control
Whenever, a local mesh control is created, it is listed in the tree view.
By double clicking the mesh control, the “Mesh Control Parameters” dialog box will open with all values set. These vales can be modified and saved.
Select a face, right click and select “Local Meshing Parameters”. This opens the mesh control assigned to the selected face. This will work for bodies, faces and edges.

36. Mesh Control Specification
Exporting a mesh control
The Mesh control created can be saved in an external file, called "Mesh Specification" and the saved file can be imported back into SimLab. This is very useful when meshing models of similar types when the mesh control created for one can be reused for the others.

37. Mesh Control Specification
Exporting a mesh control
This has 4 options,
Template
Mesh control parameters will be stored along with the geometry type associated with it, (like FACE, EDGE)
Useful for assigning mesh control for models of the same type
Body
Mesh control parameters will be stored along with the entity id.
Useful for re-meshing the same model several times or the same model with small changes in the CAD file.

38. Mesh Control Specification
Exporting a mesh control
Color
Mesh control parameters will be stored along with the color associated with it.
Useful for assigning mesh control for models based on color.
Groups
Mesh control parameters will be stored along with the group name associated with it.
Useful for assigning mesh control for models based on groups.

39. Mesh Control Specification
Importing a mesh control
Select a body to which the mesh control is to be assigned.
Open the “Mesh Control Parameters” dialog box and select “Import File”
Choose the mesh control file (with extension .xml).
This will load all the mesh controls defined in the mesh control file.
Go to the “Mesh Control” dialog box to see the imported mesh controls in the tree view.
If template mesh spec is used, select bodies, faces, edges or features and assign it to the mesh control.

40. Automation
It is common to find several cylinders with the same axis but separated by discs, cones or circular edges.
It is sufficient to assign mesh control to one or part of a circular edge and all the edges will pick up the mesh seed.
It is sufficient if the axial mesh size if assigned to one cylinder and all cylinders will pick it up.
This transmission of the mesh size will stop if the circular disk separating the cylinders is too thick.