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January 20, 2013, 10:55 |
Null determinant cells in Netgen
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#1 |
Senior Member
Daniele Vicario
Join Date: Mar 2009
Location: Novara, Italy
Posts: 142
Rep Power: 17 |
Meshing a simple geometry using Netgen I obtained some null-determinant cells that crash a solver (see http://www.cfd-online.com/Forums/ope...tml#post402809)
Enclosed you can find pictures of the mesh and the file of the .brep geometry. The white coloured cells are the null-determinant ones. Is there anyone able to solve this problem ? Is there any guideline to follow to avoid this cells ? More: Why did they come in such a simple case ? Thanks.
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Daniele Vicario blueCFD2.1 - Windows 7 |
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January 24, 2013, 06:23 |
Success in SALOME
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#2 |
Member
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I generated both meshes in SALOME without any problem.
1. Simple mesh NETGEN 1D-2D-3D with very fine settings. asd.jpg 2. Mesh with refinement on edges. v2ref.jpg I did not mesh conversion due to i have not OF on my working computer, but SALOME didn't detect zero volumes so i think there is no elements with negative determinant. P.S. I use SALOME on Win7 |
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January 24, 2013, 08:34 |
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#3 |
Senior Member
Daniele Vicario
Join Date: Mar 2009
Location: Novara, Italy
Posts: 142
Rep Power: 17 |
Hi,
Thanks for your time. Have you tried to check your mesh with: checkMesh -allGeometry -allTopology and see how many (and if...) undeterminet cells it has ? BTW: I use Salome but just to preprocess existing STEP geometry. Then usually I use SHM. I tried several times meshing with it but I found it quite instable (i.e. lots of crash), above all making submesh. Which version are you using ? Do you download it from the official site ?
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Daniele Vicario blueCFD2.1 - Windows 7 |
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January 24, 2013, 10:55 |
Mesh OK
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#4 | |
Member
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Here my checkMesh output:
Code:
Checking geometry... Overall domain bounding box (-0.05 -0.05 0) (0.05 0.05 0.375) Mesh (non-empty, non-wedge) directions (1 1 1) Mesh (non-empty) directions (1 1 1) Boundary openness (-8.45579e-18 -2.98649e-18 -1.5611e-17) OK. Max cell openness = 2.74985e-16 OK. Max aspect ratio = 4.80757 OK. Minumum face area = 6.88965e-07. Maximum face area = 0.000152252. Face area magnitudes OK. Min volume = 3.02192e-10. Max volume = 6.23914e-07. Total volume = 0.00198994. Cell volumes OK. Mesh non-orthogonality Max: 50.6206 average: 15.2056 Non-orthogonality check OK. Face pyramids OK. Max skewness = 0.557965 OK. Coupled point location match (average 0) OK. Mesh OK. Quote:
I use version 6.4 32-bit from official website. |
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January 24, 2013, 12:34 |
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#5 |
Senior Member
Daniele Vicario
Join Date: Mar 2009
Location: Novara, Italy
Posts: 142
Rep Power: 17 |
Can you please execute checkMesh with -allGeometry -allTopology options ?
PS. I really hope you had find a good way to avoid these cells... Thanks.
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Daniele Vicario blueCFD2.1 - Windows 7 |
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January 25, 2013, 09:19 |
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#6 |
Member
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OK!
I executed it with options -allGeometry -allTopology and got an undetermined cells as you describe. It was pretty strange so i did checkMesh with the same options but on my nozzle head case. The mesh was also generated using SALOME. So i got same cells in the similar positions as in your case. There is: funny.jpg So i think you need keep it simple) it's not your fault |
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