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decomposePar corrupting mesh

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Old   November 16, 2012, 10:57
Default decomposePar corrupting mesh
  #1
ski
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Hi all,

I have a mesh which passes checkMesh serial no problems. However if I use decomposePar, and run checkMesh in parallel, it fails for the same mesh as follows:

====================

Face pyramids OK.
***Max skewness = 4.28888, 475 highly skew faces detected which may impair the quality of the results
<<Writing 475 skew faces to set skewFaces
Coupled point location match (average 2.60702e-16) OK.

Failed 1 mesh checks.

====================
The number of skewed faces depends on the number of processors I use (with greater #processors seemingly corrupting the mesh more)

My decomposeParDict:

====================
numberOfSubdomains $NSLOTS ;

method scotch;


preservePatches
(
cyc_half0
cyc_half1
);
====================

I have cyclic boundaries in spanwise direction (which are exactly the same on patch cyc_half0 and cyc_half1). Not sure if this could have an effect?

Any suggestions?

Thanks
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Old   November 19, 2012, 08:25
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ski
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Does anyone else see this happen at all? The mesh does seem to work OK, but it strikes me as odd that the cell quality should deteriorate by domain decomposition. decomposePar should not be affecting the coordinates of the mesh vertices, so this shouldn't happen...

Is this a bug?



Quote:
Originally Posted by ski View Post
Hi all,

I have a mesh which passes checkMesh serial no problems. However if I use decomposePar, and run checkMesh in parallel, it fails for the same mesh as follows:

====================

Face pyramids OK.
***Max skewness = 4.28888, 475 highly skew faces detected which may impair the quality of the results
<<Writing 475 skew faces to set skewFaces
Coupled point location match (average 2.60702e-16) OK.

Failed 1 mesh checks.

====================
The number of skewed faces depends on the number of processors I use (with greater #processors seemingly corrupting the mesh more)

My decomposeParDict:

====================
numberOfSubdomains $NSLOTS ;

method scotch;


preservePatches
(
cyc_half0
cyc_half1
);
====================

I have cyclic boundaries in spanwise direction (which are exactly the same on patch cyc_half0 and cyc_half1). Not sure if this could have an effect?

Any suggestions?

Thanks
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Old   November 19, 2012, 14:46
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  #3
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Chris L
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Try

preservePatches (cyc_half0);
preservePatches (cyc_half1);

preservePatches may only take 1 augment.
I detailed my cyclic BC issues in the following thread:

Cyclic Mesh Error
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Old   November 20, 2012, 07:51
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ski
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Quote:
Originally Posted by vbchris View Post
Try

preservePatches (cyc_half0);
preservePatches (cyc_half1);

preservePatches may only take 1 augment.
I detailed my cyclic BC issues in the following thread:

Cyclic Mesh Error
Thanks for the tip. I was not aware of this. Although it has not solved the problem sadly. checkMesh is still reporting highly skewed cells.
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