| jet_engine |
June 24, 2016 06:17 |
Remove snappyHexMesh bad cells (subSetMesh)
Hi! I'm using snappyHexMesh to mesh around a plate and a cylinder and apparently I am having some problems with the addLayers step. Layers are created, but after creating them and running checkMesh, 9 severe errors appear and unfortunately, it is impossible to simulate with this mesh (floating point exception)
After modifying every single parameter in sHM's Dict with no successful results, I have decided to use subSetMesh utility, in order to create a topoSetDict and then, remove those cells so that my mesh passes successfully the mesh check and therefore, I will probably be able to simulate.
The problem is that I do not know how to select those cells. How could it be done? (I think the only needed aspect is the cell ID but I have no idea how to obtain just the IDs of the "bad" cells, does anyone know?)
This is the checkMesh output, just in case it helps:
Code:
Enabling all geometry checks.
Checking geometry...
Overall domain bounding box (-0.225 -0.35 -0.125) (1.12 0.35 0.84)
Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
Mesh has 3 solution (non-empty) directions (1 1 1)
Boundary openness (-5.87433e-16 6.97082e-17 -1.48306e-13) OK.
***High aspect ratio cells found, Max aspect ratio: 1.24904e+94, number of cells 35
<<Writing 35 cells with high aspect ratio to set highAspectRatioCells
Minimum face area = 5.21919e-10. Maximum face area = 0.00357495. Face area magnitudes OK.
***Zero or negative cell volume detected. Minimum negative volume: -6.5735e-10, Number of negative volume cells: 35
<<Writing 35 zero volume cells to set zeroVolumeCells
Mesh non-orthogonality Max: 179.989 average: 7.91616
*Number of severely non-orthogonal (> 70 degrees) faces: 115.
***Number of non-orthogonality errors: 109.
<<Writing 224 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 240 faces are incorrectly oriented.
<<Writing 183 faces with incorrect orientation to set wrongOrientedFaces
***Max skewness = 16.2622, 20 highly skew faces detected which may impair the quality of the results
<<Writing 20 skew faces to set skewFaces
Coupled point location match (average 0) OK.
***Error in face tets: 717 faces with low quality or negative volume decomposition tets.
<<Writing 318 faces with low quality or negative volume decomposition tets to set lowQualityTetFaces
Min/max edge length = 2.07766e-05 0.0607762 OK.
*There are 66069 faces with concave angles between consecutive edges. Max concave angle = 89.3598 degrees.
<<Writing 66069 faces with concave angles to set concaveFaces
Face flatness (1 = flat, 0 = butterfly) : min = 0.0400623 average = 0.999966
*There are 86 faces with ratio between projected and actual area < 0.8
Minimum ratio (minimum flatness, maximum warpage) = 0.0400623
<<Writing 86 warped faces to set warpedFaces
Cell determinant (wellposedness) : minimum: 9.01638e-05 average: 10.1297
***Cells with small determinant (< 0.001) found, number of cells: 4
<<Writing 4 under-determined cells to set underdeterminedCells
***Concave cells (using face planes) found, number of cells: 590857
<<Writing 590857 concave cells to set concaveCells
Face interpolation weight : minimum: 0.01328 average: 0.478489
***Faces with small interpolation weight (< 0.05) found, number of faces: 11
<<Writing 11 faces with low interpolation weights to set lowWeightFaces
Face volume ratio : minimum: -10.9825 average: 0.902224
***Faces with small volume ratio (< 0.01) found, number of faces: 142
<<Writing 142 faces with low volume ratio cells to set lowVolRatioFaces
Failed 10 mesh checks.
End
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