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problems with VERY simple mesh

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Old   October 17, 2006, 01:21
Default problems with VERY simple mesh
  #1
Ralf Schmidt
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Hi!

I have a very simple mesh in gambit (2D, about 5000 tri cells, only 10 cells with an equiSize Skew higer than 0.22).

Now, exporting to and importing in Fluent is no problem. Performing a grid check is ok as well. Now, I turned the solver to axissymmetric and activate k-epsilon modell. After that, a new grid chek failed:

WARNING: non-positive volumes exist.

Waht happend???

ANY idea??

Ralf
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Old   October 17, 2006, 01:24
Default Re: problems with VERY simple mesh
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mAx
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check if your revolution axis is absolute coincident with your x-axis
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Old   October 17, 2006, 01:35
Default Re: problems with VERY simple mesh
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Claud
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and it should be only in positive direction on both axis.
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Old   October 17, 2006, 01:37
Default Re: problems with VERY simple mesh
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Ralf Schmidt
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Hi, thx for answer...

that might be the problem, but: First, I had the axis BC parallel to the y-axis, now it is coincident to the x-axis. But the problem still appears when i turn on the axis-symmetric solver.

Ralf

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Old   October 17, 2006, 01:45
Default Re: problems with VERY simple mesh
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Ralf Schmidt
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it is, but that doen't help...
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Old   October 17, 2006, 02:33
Default Re: problems with VERY simple mesh
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mAx
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check if the revolution axis lie exactly on the x-axis. a small gap about 1e-3 under the x-axis will crash the grid check
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Old   October 17, 2006, 05:54
Default problem solved!
  #7
Ralf Schmidt
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Hi!

in the domain extents it is visible: the y domain starts from -1.2 e-14 - so there are some nodes below the x-axis!!

I solved the problem - editing the msh file: exchanging all y values below 0 to 0. Another way: translating the whole mesh in y-direction.

It works fine now... but why does fluent (or gambit) produces that problem???

Ralf
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Old   October 17, 2006, 07:21
Default Re: problems with VERY simple mesh
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sach
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hey have you checked right handed ness or left handed ness problem
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