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controlling unstructured mesh growth

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Old   October 21, 2005, 14:53
Default controlling unstructured mesh growth
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tucker
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I'm wondering if any of you have had any difficulties controlling the growth rate of unstructured volume meshes.

I have a simple 3D cube and I'm trying to increase volume element size as you move across the cube. I've specified the mesh distribution on my edges, and even the mesh on the faces of the cube look good. However when I mesh the volume, the interior mesh quickly blows up rather than gradually increasing in size from one side to the other.

I've tried looking for some method to control the volume growth (like an option I can select), but have been unsuccessful. Do you all have any ideas?

Thanks!
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Old   October 22, 2005, 11:28
Default Re: controlling unstructured mesh growth
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Jason
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This is an issue with the unstructured meshing algorithm built into Gambit. There are ways of controlling it (by decomposing the volume and I believe there is a default value to help smooth this growth out), but even that's not great, and it's a pain in the a$$. Use sizing functions. It's under the tools. They're described pretty well in Gambit's modeling guide. I'll use the "Fixed" sizing function as an example. For this, you pick a source (which can be one or multiple vertices, edges, faces, or volumes), an attachment (which for you would be your cube... it's the geometry you want the sizing function to act across) a Start Size, growth rate, and size limit. So lets say you want a .1 mesh that grows at 10% starting from Vertex.1 and acts across Volume.1 and it grows up to a maximum mesh size of 1.2. Then your source is Vertex.1, your attachment is Volume.1, your Start size is .1, your growth rate is 1.1, and your size limit is 1.2.

There's better explainations of all the sizing functions in the Modeling guide. I also recommend looking up the presentations from the last UGM... there's a presentation on meshing tips & tricks, and has some pretty good information on sizing functions as well.

Hope this helps, and good luck, Jason
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Old   October 22, 2005, 16:36
Default Re: controlling unstructured mesh growth
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James
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Use Gridgen or ICEM CFD instead. Gambit sucks!

James
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Old   November 2, 2005, 15:27
Default Re: controlling unstructured mesh growth
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tucker
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Thanks Jason. That's really helpful...I'll give it a shot.

Tucker
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