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[snappyHexMesh] Obtaining two regions from background mesh

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Old   September 19, 2016, 02:39
Default Obtaining two regions from background mesh
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Hello everyone. I am working on a complex geometry so I need to use STL file to generate mesh. What I am doing is, I create a bounding box using blockMesh. Then, I run snappyHexMesh to obtain background mesh and this creates new boundary for me. Using this boundary, I need to split STL file as solid region and the rest of the mesh as fluid region. I run setSet to create zone from boundary:

Code:
setSet 
faceSet f0 new patchToFace myWall
cellSet c0 new faceToCell f0 any
cellZoneSet c0 new setToCellZone c0
Using this cell zone, I want to split my mesh into 2 regions. If I run
Code:
splitMeshRegions -cellZones
command, I get thousands of domains (because of porous structure). If I use cellZonesOnly option of splitMeshRegions, I get an error:

Code:
For the cellZonesOnly option all cells have to be in a cellZone.
I just need to have 2 regions. The cells in the regions are not required to be connected to each other. One of other post here suggests using topoSet but I am lost while using it. Can you help me to split my domain0 into two regions? This is the domain I am working on:



Thank you so much.

Last edited by cfdsolver1; September 19, 2016 at 21:10. Reason: image added
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Old   September 21, 2016, 16:30
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Hi,
If I understood what you want to do, I would suggest you play around with sHM. Therefore you can split your regions. I do believe topoSet would put you into trouble and make you waste a lot of time.

I think this thread is about what you want.

http://www.cfd-online.com/Forums/ope...ous-media.html

Regards,
Roberto
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Old   September 21, 2016, 19:38
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Dear Roberto,

Thank you so much for your reply. I am able to obtain a mesh using sHM like the post you posted but my problem is, If I use sHM I get the solid region as a boundary. However, I want to name my STL file as cellZone; not as boundary. Is this possible with sHM?
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Old   September 23, 2016, 11:18
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Hi,

Have you tried the option "cellZoneInside inside;" and the associated ones as stated in slide 31 here: http://openfoamwiki.net/images/f/f0/...SlidesOFW7.pdf

Does it do what you want?

Cheers,
Antimony
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Old   September 26, 2016, 12:53
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Hello again, thanks for the tips. I guess I was able to split mesh into two regions but I am not sure if I did it correctly or not. I used
Quote:
setSet
and starting from boundary, I created a cell zone and inverted it and obtained second zone. Then I applied
Quote:
splitMeshRegions -cellZonesOnly
and created two zones and I was able to run chtMultiRegionSimpleFoam but I have a problem.

If I run chtMultiRegionSolver, the h equation at fluid region decreases and goes to minus values, which is of course wrong. If I solve solid region only, everything is okay. If I run only fluid region using chtMultiRegionSolver, it doesn't work again. So, what might be problem? Can you help me? If I use
Quote:
checkMesh -region fluid
I think everything looks okay. How can I ensure if the problem is boundary conditions or model, or mesh?
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