[snappyHexMesh] SnappyHexMesh: parameter & refinement choice

marango · August 19, 2011, 02:03

Hi @ all,

for a few weeks I'm working with OpenFOAM 2.0.0. So I don't have much experience working with it.

Now I'd like to mesh a complex geometry with snappyHexMesh. Snappy is working fine and the created mesh looks good, but when I check the mesh with checkMesh some errors occur, like:

***Error in face pyramids: 45 faces are incorrectly oriented.
<<Writing 45 faces with incorrect orientation to set wrongOrientedFaces
***Max skewness = 6.578289, 3 highly skew faces detected which may impair the quality of the results
<<Writing 3 skew faces to set skewFaces

It gets even worse when I do further refinements.

I guess there are several ways to avoid these errors. So I tried to change some parameters in snappyHexMeshDict but without success. The mesh quality didnt raise. So, can anybody give me some advice, what's a good choice for parameters in snappyHexMeshDict?

Another point I'd like to know is the choice of refinement. Is it better to generate a coarse mesh with blockMesh and do the refinement with snappy or to make a fine mesh with blockMesh and less refinement with snappy?

Thanks a lot for your help.

Marango

val46 · August 29, 2011, 07:15

Hi marango,

I also experienced these wrong oriented faces with OF2.0.0
Before I had never such an error. It could be this error comes from the new snap feature although I'm not sure.

marango · August 30, 2011, 04:08

Thanks val46 for your reply. That's a good hint and I try find out whether the error is created by the new feature.

I also tried another way. I decreased the mesh quality and chose a very low value for minTetQuality. Now the error didn't appear but the the generated mesh was not usable. I guess the problem could also be a matter of finding the right parameters for snappy...

August 19, 2011, 02:03	SnappyHexMesh: parameter & refinement choice	#1
marango New Member Join Date: Jun 2010 Location: Germany Posts: 13 Rep Power: 15	Hi @ all, for a few weeks I'm working with OpenFOAM 2.0.0. So I don't have much experience working with it. Now I'd like to mesh a complex geometry with snappyHexMesh. Snappy is working fine and the created mesh looks good, but when I check the mesh with checkMesh some errors occur, like: *Error in face pyramids: 45 faces are incorrectly oriented. <<Writing 45 faces with incorrect orientation to set wrongOrientedFaces *Max skewness = 6.578289, 3 highly skew faces detected which may impair the quality of the results <<Writing 3 skew faces to set skewFaces It gets even worse when I do further refinements. I guess there are several ways to avoid these errors. So I tried to change some parameters in snappyHexMeshDict but without success. The mesh quality didnt raise. So, can anybody give me some advice, what's a good choice for parameters in snappyHexMeshDict? Another point I'd like to know is the choice of refinement. Is it better to generate a coarse mesh with blockMesh and do the refinement with snappy or to make a fine mesh with blockMesh and less refinement with snappy? Thanks a lot for your help. Marango kflora likes this.

August 29, 2011, 07:15		#2
val46 Member Join Date: Nov 2009 Location: Germany Posts: 96 Rep Power: 16	Hi marango, I also experienced these wrong oriented faces with OF2.0.0 Before I had never such an error. It could be this error comes from the new snap feature although I'm not sure. __________________ "When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first." Werner Heisenberg

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August 30, 2011, 04:08		#3
marango New Member Join Date: Jun 2010 Location: Germany Posts: 13 Rep Power: 15	Thanks val46 for your reply. That's a good hint and I try find out whether the error is created by the new feature. I also tried another way. I decreased the mesh quality and chose a very low value for minTetQuality. Now the error didn't appear but the the generated mesh was not usable. I guess the problem could also be a matter of finding the right parameters for snappy...