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 Nick R March 10, 2011 07:24

growth rate of mesh in ICEM

Hi,

This is a basic question from a newbie. How do you control the growth rate of mesh in ICEM. Say you have a 3d wing in a box-like domain and you wish to control the way the mesh grows from the 3d wing. Is there a way you can control how fast the mesh would grow from the wing into the domain? Is there a face size growth parameter?
BTW this question is in the tetra unstructured strategy approach.

Thanks.

Nick

 alastormoody11 March 11, 2011 06:25

There are two ways to do this

First is to assign a very small mesh size on the surface of the 3D wing, which would essentially ensure a fine mesh size at least in the proximity of the wing, also the region in a in which grid is fine can be increased by using slower transition.

If you want a considerable area around the 3D wing to have a very fine mesh you will need to create a mesh and then assign a small value for the grid size inside the density.

You can use the two in combination.

 PSYMN March 11, 2011 11:53

Tetra Ratio...

Under the mesh tab => Params by Parts, you have various columns for settings. You can also apply these to individual surfaces or curves... The Tetra ratio is the growth rate into the volume. The Width will fix the size on a number of elements into the volume before the transition begins.

With Octree Tetra, the sizes really grow by powers of 2. So the ratio applies over the longer term.

Delaunay 1 1.2 1.4 1.7 2.1 2.5 3.0 3.6 4.3
Octree 1 1 1 1 2 2 2 2 4

In the above two rows, the ratio is set to 1.2 for both, but the Octree mesh appears to stay as size 1 for 4 layers and then jumps to size 2... Over the long term, the octree growth rate is approximately 1.2.

If you want actual smooth transitions, just remesh your Octree mesh (keeping the surface mesh) with Delaunay.

Alastormoody is talking about density boxes (or points or lines), which is a way to set the local max size within a volume. You can also set a growth ratio on each density which affects the transition away from the density.

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