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Introductory GAMBIT Notes

GAMBIT v2.1 Jul 2003

Volume Decomposition Examples

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Decomposition

Suggestions of how to decompose single volumes into multiple mesh-able

volumes are shown in these examples.

The following meshing tools are used:

Map Submap

Tet-primitive

Cooper

Volume decomposition is not needed for the Stairstep, Hex/Core or TGrid

Tet/Hybrid meshing schemes.

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First Example (1) A spherical void inside a brick

Construction

Create a sphere, a brick and a cylinder using volume primitives. The cylinder diameter

should be smaller than the sphere and its length extending outside the brick

Subtract the sphere from the brick

Decomposition

Split the brick using the cylinder

Create edges going diagonally over the top and bottom face of the brick and use the

edges to create a diagonal face

Split the brick-like volume using this face

Last two steps are not necessary but create higher quality mesh.

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First Example (2)

A spherical void inside a brick

Three of the four Cooper-able volumes

source faces

source faces

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Second Example (1)

A handle Construction:

Create a torus and a brick using volume primitives

Split the torus using the brick Face as a tool

Delete the left part of the torus

Decomposition:

Make a Bidirectional split of the remaining volumes

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Second Example (2)

A handle Alternative Construction/Decomposition:

Create a torus and a brick using volume primitives

Perform a bi-directional split using the two volumes

Delete the part of the torus that is outside the back of the brick

Unite back the block and the pipe section inside the block again

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Second Example (3)

A handle The two volumes meshed by the Cooper - tool

source faces

source face

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Third Example (1)

A box with rounded corners

Construction

Create a brick using volume primitives

Use the blend option to round off one corner and three edges using the same

radius (Setback option)

Decomposition: Create a second brick of the same size as the radius of the blend and move it

such that its corner coincides with the center point of the blended corner.

Split off the the rounded corner

Sweep out the three triangular faces created by the split to the opposite ends

of the brick

Split off the three prismatic volumes from the main volume

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Third Example (2)

A box with rounded corners

The volume can be meshed using the submap (1), the tet-primitive (not

shown) and the Cooper (3) schemes.

source facessource

face

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Fourth Example (1)

Pipe-pipe intersection (different radii) Construction:

Create the pipes using volume primitives

Create a stretched brick with a rectangular cross-section, where the side

length should be between the two pipe diameters.

Decomposition

Split the main pipe using the brick

Unite the brick cut-out with the small cylinder

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Fourth Example (2)

Pipe-pipe intersection (different radii)

The three volumes meshed using the Cooper tool

source faces

source faces

source faces

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Fifth Example (1)

A sphere in three volumes

Construction

Create a sphere using volume primitives

Decomposition:

Create a cylinder and split the sphere using the cylinder

Create a brick and move it such that one side of the brick is along the center of

the cylinder

Split the annular remainder of the sphere into two volumes

All three volumes are basic Cooper-able volumes

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Fifth Example (2)

A sphere

The final mesh for two of the volumes

source faces

source faces

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Fifth Example (3)

A sphere in eight volumes

Alternative Construction/decomposition

Create a sphere and a brick using volume primitives

Intersect the two volumes to create a sphere octant

Make a second copy by the use of Copy/Reflect and the z-plane

Make six octants more using Copy/Rotate and 90 degree angle, twice

Connect all faces using Real Connect

The same geometry could also have been created by splitting a sphere in all

three major planes

This decomposition will create a better mesh quality

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Fifth Example (4)

A sphere

The final mesh for seven out of the eight octants, all meshed using

Tet Primitive

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