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Old   November 30, 2008, 03:03
Default GRIDGEN BLOCK Extrusion
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I have a 2 dimensional grid (using GRIDGEN) I am trying to extrude from this a 3 D grid, but am unable, I get the following message Extrusion process stopped since a cell contains POS SKEW jacobian. How can I fix this?


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Old   December 1, 2008, 23:53
Default Re: GRIDGEN BLOCK Extrusion
Chris Sideroff
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The layman's explanation of POS SKEW, is that it is an indication that a cell(s) most likely has a concave face pair. Most solvers do not handle concave faces well or at all. I would try to illustrate what I mean but the auto-formatting of forum screwed up my ASCII art.

Getting back to your problem there are a couple of things you try to avoid getting POS SKEW cells.

The most obvious is to improve the quality of the domain you are beginning the extrusion with. Use the Structured Solver to improve the quality by smoothing it. Refer to the user manual for explanations of all the settings.

You didn't indicate what type of extrusion you trying. If it is the hyperbolic or algebraic there are additional parameters for smoothing the extrusion as it proceeds. Again refer to the user manual for details on these controls.

The last and not recommended option is disable the POS SKEW stopping criterion. *ONLY* do this if you are sure your solver can handle these types of cells.

Let me know if want the exact (mathematical) definition.
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Old   December 8, 2008, 21:21
Default Re: GRIDGEN BLOCK Extrusion
Wifi Lee
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I can gridding it for you.Can you send your model to me?
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