ANSYS Workbench M hiMeshing

August 30, 2012

© 2012 CAE Associates

Agenda

Why do I want a brick mesh? Why do I want a brick mesh?

How can I get a brick mesh in ANSYS Workbench?

Live demonstration

2

How Do I Get a Brick Mesh?

Why do I want a brick mesh? Why do I want a brick mesh?— 3D solid elements generally come in a few basic shapes:

• Hexahedron (hexas, bricks)• Pentahedron (wedges prisms degenerate bricks)Pentahedron (wedges, prisms, degenerate bricks)• Tetrahedron (tets)• Pyramid (less common, but essential for mixing tets and bricks)

— Hexahedrons can fill a given volume more efficiently than other mesh shapes

Hex Pyramid Tet Wedge

— Hexahedrons can fill a given volume more efficiently than other mesh shapes• It takes approximately 5-6 tetrahedrons to fill 1 brick.• Fewer elements lead to faster solution times

— Hexahedron meshes are generally more uniform

3

g y• Easier control of the element distribution

How Do I Get a Brick Mesh?

What Steps Do I Need to Take? What Steps Do I Need to Take?— Brick meshes always take more man-time than tetrahedral meshes. — Brick meshes are usually created using one or more of the following

approaches:approaches:• Slice and dice the solid geometry to create 6-faced volumes, each face having 3 or

4 boundary curves.• Create a 2D mesh of quadrilaterals and sweep or extrude the 2D mesh to create 3D

b i k T i l ti i l dbricks. Typical operations include:— Revolve the mesh about an axis.— Sweep the mesh along one or more curves.— Sweep a surface mesh from one face of a volume to a topologically similar face on the

“opposite” face of a volume.

— Brick meshes can also be created with advanced meshing methods.

4

How Do I Get a Brick Mesh?

Consider the part shown below While not sweepable in its present form Consider the part shown below. While not sweepable in its present form, an all-brick mesh can be created with some effort by the user.

5

How Do I Get a Brick Mesh?

By creating a few slices in By creating a few slices in DesignModeler and forming the resulting bodies into a part, we can get a collection of sweepablecan get a collection of sweepablebodies.

The mesh is generated to ensure The mesh is generated to ensure 3 elements through the thickness of the thin walls.

The resulting mesh of higher order elements contains 8,208 elements and 42 540 nodeselements and 42,540 nodes.

6

How Do I Get a Brick Mesh?

The corresponding all The corresponding all tetrahedron mesh resulting from the unaltered geometry is shown to the right.to the right.

Again, the mesh is generated to ensure 3 elements through theensure 3 elements through the thickness of the thin walls and is meshed with very little effort.

The resulting mesh of higher order elements contains 84,168 elements and 130 573 nodes!elements and 130,573 nodes!

7

How Do I Get a Brick Mesh?

So How Do I Get a Brick Mesh in Workbench? So How Do I Get a Brick Mesh in Workbench?— Several Mesh Methods will create Brick meshes

• Sweep• Hex DominantHex Dominant• Multizone

— Each method has different geometry requirementsg y• Important to understand how they behave!

— What if I can’t get a mesh that’s entirely bricks?• Selective meshing to the rescue!

8

Mesh Methods

Mesh > Sweep Mesh > Sweep— Sweep requires topologically consistent source and target faces (same number

of vertices per face with a smooth path from the source to the target). — Sweep is the default Workbench meshing approach if a body cannot be sweptSweep is the default Workbench meshing approach, if a body cannot be swept

it is free meshed with tetrahedral elements. — Specify manual source (and target faces) when:

• There exists more than one possible sweep direction• You want to sweep mesh a thin solid with a single element through the thickness• You want to inflate the mesh near the surface of the geometry

9

Mesh Methods

Mesh > Sweep Mesh > Sweep— The number of elements in the sweep direction along with the bias settings are

also set in the sweep details.

10

Mesh Methods

The Hex Dominant method creates a primarily quadrilateral mesh on the The Hex Dominant method creates a primarily quadrilateral mesh on the outer surface topology and sweeps inward. It blends the disparate hex mesh patterns internally using wedges, pyramid and tetrahedral elements.

The Hex Dominant method works well on bodies with a high volume to The Hex Dominant method works well on bodies with a high volume to surface area ratio.

11

Mesh Methods

The mesh metrics can be used to determine if the mesh is actually hex The mesh metrics can be used to determine if the mesh is actually hex dominant.

12

Mesh Methods

The MultiZone Method uses the Hexa blocking method (courtesy of the The MultiZone Method uses the Hexa blocking method (courtesy of the ICEM Advanced Meshing Module) that internally segments bodies into topologically consistent pieces.

13

Combining Methods

Mesh methods defined on individual bodies are valid when those bodies Mesh methods defined on individual bodies are valid when those bodies are formed into a part.

14

Selective Meshing The Worksheet captures body order for Selective meshing The Worksheet captures body order for Selective meshing.

— Named selections are created and sent to the solver (element components). — Note: The automatic method is still used for mixed order meshing of parts.

15

Summary

Brick meshes are more efficient and controllable Brick meshes are more efficient and controllable

Many different options within ANSYS Meshing for generating a brick mesh

Ease of use of ANSYS Workbench makes generating brick meshes simpler

16