| Eloise |
August 26, 2014 07:10 |
How to iddentify and get rid of cells with too small volume?
Hello Foamers,
I am working on the layer addition phase for a complex snappyHexMesh (sHM) mesh. I encountered a crash of sHM with the error message:
Code:
#1 Foam::sigFpe::sigHandler(int) in "/share/apps/OpenFOAM-2.2.2//OpenFOAM-2.2.2/platforms/linux64Gcc46DPOpt/lib/libOpenFOAM.so"
which I overcame by unsetting FOAM_SIGFPE before generating my mesh.
Now that sHM runs until the end, I get a mesh with layers but it's quality is not sufficient. As shown by checkMesh output, I have some cells with minimum volume of magnitude e-300:
Code:
Checking geometry...
Overall domain bounding box (-140 -140 -300) (140 140 0.000368027)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-nan nan -nan) OK.
Max cell openness = 6.65112e-16 OK.
Max aspect ratio = 24.5205 OK.
Minimum face area = 3.61586e-06. Maximum face area = 149.753. Face area magnitudes OK.
Min volume = 1.66667e-300. Max volume = 518.268. Total volume = 1.83588e+07. Cell volumes OK.
Mesh non-orthogonality Max: 64.9964 average: -nan
Non-orthogonality check OK.
Face pyramids OK.
***Max skewness = 49.8663, 6557 highly skew faces detected which may impair the quality of the results
<<Writing 6557 skew faces to set skewFaces
Coupled point location match (average 0) OK.
Failed 1 mesh checks.
I run sHM layer phase with the following relaxed mesh quality:
Code:
relaxed
{
maxNonOrtho 65;
maxBoundarySkewness -1;
maxInternalSkewness -1;
maxConcave 180;
minVol 1e-6;
minArea 1e-6;
minTetQuality -1e30;
minTwist -1e30;
minDeterminant -1;
minFaceWeight -1;
}
But at the end of sHM, I see in the output that 153 cells still don't respect the minimum volume criteria:
Code:
[...]
Setting up information for layer truncation ...
Checking mesh with layer ...
Checking faces in error :
non-orthogonality > 65 degrees : 0
faces with face pyramid volume < 1e-06 : 153
faces with area < 1e-06 m^2 : 0
Detected 153 illegal faces (concave, zero area or negative cell pyramid volume)
Extruding 125954 out of 128858 faces (97.7%). Removed extrusion at 0 faces.
Added 125954 out of 128858 cells (97.7%).
Edge intersection testing:
Number of edges : 29892999
Number of edges to retest : 0
Number of intersected edges : 2258776
Doing final balancing
---------------------
Writing 125954 added cells to cellSet addedCells
Writing 0 faces inside added layer to faceSet layerFaces
Layer mesh : cells:8664071 faces:29892999 points:12677767
Cells per refinement level:
0 8664071
Writing mesh to time 3
Wrote mesh in = 346 s.
Layers added in = 346 s.
Finished meshing in = 391 s.
End
My questions are:
1. I would like to know where are the problematic faces/cells but checkMesh does not isolate them in a face or cell set. How can I create a set of cells which have a volume lower than 1e-6?
2. Which quality criteria or sHM criteria will force the cells volume to be above 1e-6?
Thanks for reading me :)
Regards,
Eloïse |
