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[blockMesh] Odd cell distortion when meshing a sphere in BlockMesh or SnappyHexMesh

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Old   February 19, 2020, 12:50
Default Odd cell distortion when meshing a sphere in BlockMesh or SnappyHexMesh
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I am trying to generate a 3D mesh of a sphere for OpenFOAM. I have tried generating it using an STL file and SnappyHexMesh, as well as using the attached m4 file to generate a blockMeshDict (also attached). (from this post)


No matter what I try, I always get this odd "finger" in the resulting mesh as shown in the attached image (from the sphere to the "bottom" of the image). This happens with both methods, so suspect that there might be a systematic mistake behind this.


Can anyone give me a hint how to get rid of that? Is this maybe just a rendering artefact caused by ParaView?


System Info:

System 1: Kubuntu 19.10, OpenFoam 1906, Paraview 5.7.0

System 2: Windows 10, OpenFoam 1912 (running on WSL), Paraview 5.8.0 RC2 (on Windows)

System 3: Ubuntu 18.04.4 (LTS), OpenFoam 1912, Paraview 5.7.0
Attached Images
File Type: jpg Screenshot_20200219_173817.jpg (156.3 KB, 46 views)
Attached Files
File Type: txt blockMeshDict.m4.txt (40.9 KB, 0 views)
File Type: txt blockMeshDict.txt (29.4 KB, 1 views)
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Old   February 19, 2020, 18:31
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paraview, dont worry.

but `checkMesh -allTopology -allGeometry` might be helpful as well.
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Old   February 20, 2020, 04:21
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As HPE said, this is an artifact in ParaView which depends on the slice position relatively to the mesh.

To get rid of it, you can check the "crinkle slice" option when creating your slice in ParaView (there is an equivalent option with the clip filter too)
Another way to solve this issue is to slightly move your slice, but it may create another artifact somewhere else.

Anyway, no need to worry, this is just related to visualization.

Cheers,
Yann
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Old   February 20, 2020, 04:35
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Thanks everyone, that helped a lot!



Ran `checkMesh -allTopology -allGeometry` and found some small issues to look into. And "Crinkle Slice" helped a lot as it allowed me to see that there are actually no problems at that "finger" (but found some minor things somewhere else).
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