[snappyHexMesh] ignored parts of geometry during refinement

Eloise · September 18, 2012, 07:37

Hello,

A part of my geometry is composed of poles, for which I impose a given refinement level. Most of the poles are refined as expected, but some of them are ignored in the refinement stage. They end up with very large resolution (see attached image).
Do you know how I can avoid this?

Remarks:
- The maximum amount of cells is not reached during castellation step.
- minRefinementCells was set to 0 without any impact.
- all the poles are part of the same STL input file and should therefore be treated the same way.

Thanks for your help,
Eloïse

Eloise · September 20, 2012, 08:26

no idea?
I must say it is not really critical in my mesh, but I'm curious to find out its reason

Tobi · September 25, 2012, 05:21

Quote:

Originally Posted by Eloise

no idea?
I must say it is not really critical in my mesh, but I'm curious to find out its reason

Hey ...
maybe your sHM stop refining couse of reaching "maxGloballCells". So if your mesh reaches that limit, sHM stop direct without refining other zone.

Set that value higher - maybe that is the solution for your problem.

Eloise · September 25, 2012, 06:15

Hi Tobi,
The maxGlobalCells is not the problem, I've already checked that point.
Thanks anyway

kalle · September 25, 2012, 06:39

Hi,

did you specify surface refinement or feature line refinement?

K

Eloise · September 26, 2012, 09:23

Hi Karl,

Surface refinement is the same for all the geometry as it comes from a single STL file.
But the feature edges refinement did the trick. All geometry is refined, and mesh quality was slightly improved. However, I haven't used the "snap to feature edges" option as this results in the following error message from sHM "Did not succesfully snap mesh. Giving up."

Thanks,
Eloïse

kalle · September 28, 2012, 01:45

I see... I was asking since there is a bug which causes snappy to ignore some refining specified on feature lines:

http://www.openfoam.org/mantisbt/view.php?id=552

Since you only specified surface refinement, you should not be affected by that.

I'd guess the error message you get is because snappy could not snap to the surface while maintaining good mesh quality... playing around with settings may help:

http://openfoamwiki.net/index.php/SnappyHexMesh

Good luck,
K

Eloise · September 28, 2012, 02:36

Hi Karl,

I am not especially looking for snapping at those feature edges so I will leave it as it is. If I had to snap, I should first increase the refinement level, but then my mesh would get very large. I have to avoid that.

I am also aware of this bug in 2.0 as I have this issue in another location in my geometry. I'm trying to upgrade to 2.1 but it is not as easy as it looks like... I hope I will soon be a part of the "2.1 foamers community"

Eloïse

September 28, 2012, 01:45		#7
kalle Senior Member Karl-Johan Nogenmyr Join Date: Mar 2009 Location: Linköping Posts: 279 Rep Power: 21	I see... I was asking since there is a bug which causes snappy to ignore some refining specified on feature lines: http://www.openfoam.org/mantisbt/view.php?id=552 Since you only specified surface refinement, you should not be affected by that. I'd guess the error message you get is because snappy could not snap to the surface while maintaining good mesh quality... playing around with settings may help: http://openfoamwiki.net/index.php/SnappyHexMesh Good luck, K aow likes this.

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September 20, 2012, 08:26		#2
Eloise Senior Member Eloïse Join Date: Jul 2012 Location: Trondheim, Norway Posts: 113 Rep Power: 13	no idea? I must say it is not really critical in my mesh, but I'm curious to find out its reason

September 25, 2012, 06:15		#4
Eloise Senior Member Eloïse Join Date: Jul 2012 Location: Trondheim, Norway Posts: 113 Rep Power: 13	Hi Tobi, The maxGlobalCells is not the problem, I've already checked that point. Thanks anyway

September 25, 2012, 06:39		#5
kalle Senior Member Karl-Johan Nogenmyr Join Date: Mar 2009 Location: Linköping Posts: 279 Rep Power: 21	Hi, did you specify surface refinement or feature line refinement? K

September 26, 2012, 09:23		#6
Eloise Senior Member Eloïse Join Date: Jul 2012 Location: Trondheim, Norway Posts: 113 Rep Power: 13	Hi Karl, Surface refinement is the same for all the geometry as it comes from a single STL file. But the feature edges refinement did the trick. All geometry is refined, and mesh quality was slightly improved. However, I haven't used the "snap to feature edges" option as this results in the following error message from sHM "Did not succesfully snap mesh. Giving up." Thanks, Eloïse

September 28, 2012, 02:36		#8
Eloise Senior Member Eloïse Join Date: Jul 2012 Location: Trondheim, Norway Posts: 113 Rep Power: 13	Hi Karl, I am not especially looking for snapping at those feature edges so I will leave it as it is. If I had to snap, I should first increase the refinement level, but then my mesh would get very large. I have to avoid that. I am also aware of this bug in 2.0 as I have this issue in another location in my geometry. I'm trying to upgrade to 2.1 but it is not as easy as it looks like... I hope I will soon be a part of the "2.1 foamers community" Eloïse