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[mesh manipulation] improveMeshQuality deletes facezones

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Old   August 18, 2022, 04:01
Default improveMeshQuality deletes facezones
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Hello everybody!


I am interested in producing usable polyhedral meshes with boundary layers and facezones. I found this thread with a procedure to create such a mesh minus the facezones :


polyDualMesh + Layers + cfMesh/improveMeshQuality = usable polyMeshes witH BLayer


I conducted some tests on a simple cylinder meshed with a facezone inside via Salome and Netgen. After polyDualMesh and combinePatchFaces, the facezone is still there, but the checkMesh returns poor quality. After running improveMeshQuality, the mesh seems usable but the facezone ID is gone, although you can see where it supposed to be in Paraview.


Does anyone have an idea on why the facezone is ignored with the improveMeshQuality tool ? I know having facezones with cfMesh is tricky, so maybe using related commands is to be avoided. Any help is appreciated, thanks !
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File Type: jpg polydualmesh_checkmesh.JPG (77.7 KB, 19 views)
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Old   August 19, 2022, 09:19
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Interesting. I never used this utility, but sometimes the easiest things work, so here is what I would try: the faces belonging to the faceZone are collected in a file in polyMesh. If improveMeshQuality does not renumber anything (does it?), then maybe you can just copy over the file to the mesh after the utility ran?
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Old   August 19, 2022, 12:44
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Quote:
Originally Posted by AtoHM View Post
Interesting. I never used this utility, but sometimes the easiest things work, so here is what I would try: the faces belonging to the faceZone are collected in a file in polyMesh. If improveMeshQuality does not renumber anything (does it?), then maybe you can just copy over the file to the mesh after the utility ran?



Okay, simplicity at its best you are a genius ! It does work, or at least it is recognized by checkMesh and Paraview (when you use the Extract Filter).


To sum up the steps to achieve a usable polyhedral mesh with Salome and polyDualMesh and preserving faceZones :

  • Import your .unv mesh
  • polyDualMesh -concaveMultiCells -overwrite [featureAngle]
  • combinePatchFaces -overwrite [featureAngle]
  • In the constant/polyMesh folder, back up the faceZones file somewhere else
  • improveMeshQuality
  • copy the backup of faceZones back in the fresh polyMesh folder


I have yet to see if nothing is out of place during an actual simulation, and to check if the same trick works for cellZones but it is very encouraging for baffles, splitting the mesh for multiregion cases etc. I will post some updates if I make progress.



Thanks again AtoHM !




Edit: it also works for cellZones
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Last edited by Alczem; August 22, 2022 at 09:05.
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Old   August 22, 2022, 11:31
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Hi all,


I did more tests with cellZones, and the improveMeshQuality seems to smooth the sharp features of the facezones.


I tried to mesh a small cube inside a bigger cube, and define it as a cellZone with a faceZone at the interface. The result of the steps I described earlier is attached: smoothed edges which mess up the cellZone and the faceZone.


Until someone finds a fix, I would recommend to set up faceZones and cellZones such that they are connected to a boundary or share a boundary with the main mesh (so avoid "floating" cellzones/facezones). It looks like it helps preserve the sharp edges.


I will try to investigate further when I have the time
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