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-   -   Getting rid of weird Tet regions in ICEM? (http://www.cfd-online.com/Forums/cfx/22678-getting-rid-weird-tet-regions-icem.html)

Chebeba June 8, 2006 13:34

Getting rid of weird Tet regions in ICEM?
 
I sometimes get regions of large size and strange aspect tets occuring in the middle of the volume mesh. They appear randomly, and the sizes are larger than Global Max Size or any Densities in the area. (Using "Tetras from Surface Mesh" with a premeshed boundary layer in ICEM 10 ServicePack2).

Sometimes just remeshing makes them go away, but now I'm stuck with a model that doesn't. Anyone knows any tricks to get rid of them?

Here is an example:

http://img245.imageshack.us/img245/5404/icemtet8md.jpg

Joe June 8, 2006 14:51

Re: Getting rid of weird Tet regions in ICEM?
 
Are you smoothing the mesh at all?

Chebeba June 8, 2006 15:49

Re: Getting rid of weird Tet regions in ICEM?
 
Well it doesn't help, once these "blobs" of too large tets are in there, smoothing doesn't make them go away.

The surface mesh is smoothed before growing the prisms of course.

Joe June 8, 2006 17:35

Re: Getting rid of weird Tet regions in ICEM?
 
Do you use a smooth transition factor when doing the tet volume mesh? If so, what value do you specify?

Chebeba June 9, 2006 04:24

Re: Getting rid of weird Tet regions in ICEM?
 
1.05 in this case. Or 1.1 or 1.06, I made different attemtps since the problem is intermittent and sometimes goes away when you remesh. But in this case it doesn't want to :( /C

Joe June 9, 2006 06:46

Re: Getting rid of weird Tet regions in ICEM?
 
Do you get the problem when the smooth transition factor is unset?

Chebeba June 13, 2006 16:20

Re: Getting rid of weird Tet regions in ICEM?
 
"Smooth Transition" is only available in "From Geometry" mode. I am using "From Surface Mesh", which doesn't have this parameter.

myron June 14, 2006 08:15

Re: Getting rid of weird Tet regions in ICEM?
 
You can try building a mesh subset of those elements and a few elements around them. Then you can remesh just that subset to see if that fixes the issue. Essentially it throws out that subset, then re-meshes based on the elements around the subset.

Glenn Horrocks June 14, 2006 17:49

Re: Getting rid of weird Tet regions in ICEM?
 
Hi,

In my experience these sort of problems are caused by mesh smoothing. The default smoothing options sometimes goes bezerk and makes horrible little bits like Chebaba is getting.

My suggestion would be to remesh the original tet mesh again and use it without smoothing, or if you must smooth do a two step smoothing where you smooth the surface elements only with a laplace smoother (with the volume elements floating) then freeze the surface elements and do a normal smooth on the volume elements.

You can also tweak the smoother by adjusting the quality to smooth up to parameter and the quality critereon - maybe an aspect ratio based criteria would help here.

Glenn Horrocks


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