copyright © 2010 altair engineering, inc. all rights reserved.altair proprietary and confidential...

Copyright © 2010 Altair Engineering, Inc. All rights reserved. Altair Proprietary and Confidential Information

Section 7

Mesh Control


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.

Mesh Control Overview


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.

Mesh Control - Classifications


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.

Global Mesh Controls


Global Mesh ControlsSurface meshing


Global Mesh ControlsVolume meshing

Input


Global Mesh ControlsVolume meshing

Output


Mesh size on geometryBodyFacesEdgesRegions (with Break option)

Mesh size on featuresFilletsCylindersWasherCircle ImprintValve Seat Pocket Iso-Line

SeedingEdges

Hard pointsFaces Edges

Preserve EntitiesFace EdgesFace shapeEdgeMeshSymmetry Mesh

Mesh Patterns IsomeshFree MeshUnion Jack

The local mesh controls available are

Local Mesh Controls


Following are the local mesh control parameters,

1. Face Mesh Control

2. Edge Mesh Control

3. Body Mesh Control

4. Fillet Mesh Control

5. Cylinder Mesh Control

6. Washer Mesh Control

7. Circle Imprint Mesh Control

8. Region Mesh Control

9. Valve Seat Pocket Mesh Control

10.Iso-Line Mesh Control

11.Volume Layer Mesh Control

Local Mesh Controls


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

1. Face 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

2. Edge 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

3. Body Mesh Control


Fillet Mesh Control is used to control the mesh over fillets along the length and the

curve direction.

Input Output Mesh

4. Fillet Mesh Control


Cylinder Mesh Control is used to control the mesh both axially and radially on the

selected cylindrical faces.

Input Output Mesh

5. Cylinder Mesh Control


Washer mesh control is used to create rings around a circle.

The circle has to be inside one face.

6. Washer Mesh Control

Input Output Mesh


Creates circular edge on a face with the specified radius and the number of seeds.

7. Circle Imprint Mesh Control

Input Output Mesh


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.



Region Mesh Control -Cylinder – Local Size – Without Break

Input



Region Mesh Control -Cylinder – Local Size – Without Break

Output



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.

9. Valve Seat Mesh Control


Input


Output

Valve Seat Mesh control without Preserve Chamfer



Valve Seat Mesh control with Preserve Chamfer

Input Output


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.

10. Iso Line Mesh Control


Input

10. Iso Line Mesh Control

Output


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.

11. Volume Layer Mesh Control


Input



Output



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

Hard Points – Mesh Control


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

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.

Preserve Entities


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.


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.

Mesh Patterns


Mesh Patterns


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.

Local Mesh Controls


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.

Modifying Local Mesh Control


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.

Mesh Control Specification



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.




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.



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.



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.

Automation

copyright © 2010 altair engineering, inc. all rights reserved.altair proprietary and confidential...

Documents

mesh control slide

output mesh

body mesh control

face mesh control

washer mesh control

edge mesh control

region mesh control

cylinder mesh control