[snappyHexMesh] Strange SnappyHexMesh behavior at the symmetry plane

ripperjack · February 3, 2017, 16:24

Dear foamers,

I am using SnappyHexMesh for a relatively simple case (symmetric geometry). I found a strange behavior that sometimes the mesh spacing suddenly becomes very small at the symmetry plane, even though the geometry is very smooth there (see the attached figure). Not sure how to avoid this. Any ideas? Thanks very much in advance!

BTW: I tried to mesh the whole geometry (without the symmetry plane) and this issue is gone. But I really want to save 50% of CPU time using half geometry.

Best regards,
Jack

me3840 · February 23, 2017, 02:09

Is that surface division where different patches/boundaries meet? I found that was the case for some of my meshes. That tet/wedge it adds can sometimes even cause zero area faces.

ripperjack · February 23, 2017, 22:43

Quote:

Originally Posted by me3840

Is that surface division where different patches/boundaries meet? I found that was the case for some of my meshes. That tet/wedge it adds can sometimes even cause zero area faces.

Thanks for your reply. And yes this only happens at the intersection between the symmetry plane and the solid body surface for my case. Do you have a solution for this?

Best,
Jack

me3840 · February 23, 2017, 23:56

No, that's not what I meant.

Does your solid body contain multiple named surfaces? This feature happened to me several times on a geometry that did, and the feature was only where the two named surfaces met the symmetry plane. I resolved it by just combining the surfaces into 1.

ripperjack · February 24, 2017, 00:03

Quote:

Originally Posted by me3840

No, that's not what I meant.

Does your solid body contain multiple named surfaces? This feature happened to me several times on a geometry that did, and the feature was only where the two named surfaces met the symmetry plane. I resolved it by just combining the surfaces into 1.

Interesting. Yes, I did separate the solid body surfaces and named them differently. I will try to combine all the surfaces. Thanks for the tip.

Regards,
Jack

ripperjack · March 3, 2017, 14:22

Quote:

Originally Posted by ripperjack

Interesting. Yes, I did separate the solid body surfaces and named them differently. I will try to combine all the surfaces. Thanks for the tip.

Regards,
Jack

Well, I tried to combine all the surfaces together and it still gave me the weird refinement at the symmetry plane....

ripperjack · March 3, 2017, 14:39

BTW: I came across this post, and temporarily changed symmetry boundary to empty. It solved the problem.

February 23, 2017, 23:56		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	No, that's not what I meant. Does your solid body contain multiple named surfaces? This feature happened to me several times on a geometry that did, and the feature was only where the two named surfaces met the symmetry plane. I resolved it by just combining the surfaces into 1. KaLium likes this.

March 3, 2017, 14:39		#7
ripperjack Member Jack Join Date: Dec 2011 Posts: 94 Rep Power: 14	BTW: I came across this post, and temporarily changed symmetry boundary to empty. It solved the problem. KaLium and crubio.abujas like this.

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February 23, 2017, 02:09		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Is that surface division where different patches/boundaries meet? I found that was the case for some of my meshes. That tet/wedge it adds can sometimes even cause zero area faces.