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[snappyHexMesh] No Boundary Layer Created in SHM

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Old   September 22, 2021, 21:39
Default No Boundary Layer Created in SHM
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GDS
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I found several previous questions like this one, but the usual recommendations have not helped. I am just trying to mesh a 2D airfoil. NASA generated some meshes for this example, and OpenFOAM produces good results using those meshes. However, the meshes were generated with some other software, which I don't have. In the meshes I have generated with SHM, the boundary layer cells are thicker than in the NASA meshes. I don't know if that is the reason the results (i.e., c_l and c_d) are not as good, but I wanted to create a finer boundary layer. Using paraFoam to measure the cells, I found that the first-layer cells in the NASA mesh are around 1e-6 m thick. The thinnest I can get out of SHM is 1e-4 m. When I try anything smaller, SHM does not create a boundary layer. For now, I am just trying to create one layer of cells. I have tried adjusting the various mesh quality parameters, but nothing helps. The final check that SHM displays does not indicate any bad cells. I am using relativeSizes=false.
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File Type: txt SHMout-3.txt (2.0 KB, 7 views)
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Old   October 2, 2021, 07:05
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I'm having a similar issue. Different geometry but the essence of the issue is the same, I can't get my first layer to be as thin as I want it (~1mm).



Have you managed to make any progress on that?
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Old   October 3, 2021, 17:18
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Not yet, unfortunately.
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Old   October 4, 2021, 03:51
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BL are a weak point of sHM. But the checkMesh output does not help, you might want to share the snappyHexMeshDict?
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Old   October 9, 2021, 18:49
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Quote:
Originally Posted by AtoHM View Post
BL are a weak point of sHM. But the checkMesh output does not help, you might want to share the snappyHexMeshDict?

Hi AtoHM,

although I'm not the original poster I have the same problem as I explained above (also in another thread here). I think both GDS and myself can benefit if you can help.


I've attached my snappyHexMeshDict and the meshQualityDict as well as the checkMesh results and the snappy log file (just the end of it, the size was prohibitive).


In the snappyHexMeshDict you'll probably see that I've used the displacementMotionSolver instead of the default one but the end result is pretty much the same (layers only grown partially on a flat surface and not with the specified 1st cell height).

Hopefully you can spot something obvious and solve our problem! lol

Thanks!
Attached Files
File Type: txt snappyHexMeshDict.txt (21.2 KB, 0 views)
File Type: txt meshQualityDict.txt (3.1 KB, 1 views)
File Type: txt checkmesh.txt (17.1 KB, 1 views)
File Type: txt snappyEnd.txt (1.8 KB, 1 views)
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