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Background Mesh in snappy with multi domain (CHT)

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Old   May 22, 2013, 18:04
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  #21
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Jackie Chou
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To post #16

Hello, Bruno,

as you said, after successful snappyhexmesh, I used surfaceToPatch to get the boundary. However, some of boundaries still have "nFaces 0", I change the tolerence from 1e-8 to 1e-5, a few faces still have "nFaces 0". Normally, boundary faces "nFaces number" will increase as the tolerence increases. Will this increase have impact on the final calculation? Some boundary faces have very low "nFaces number". I am not sure how high for this "nFaces number" is a suitable choice for the final calculation.

Do you have any experience and suggestions for this problem?

Thank you for your replies!

with best regards, good night!


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Old   May 22, 2013, 18:48
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Bruno Santos
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Hi Jackie,

My guess is that the surface is inside the mesh, which leads to it not being associated to existing boundary faces... because inside the mesh there are no boundary faces.

If I remember correctly, you're trying to re-assign patch names back to the interfaces between regions. Have you split the mesh into the separate regions?

Best regards,
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Old   May 23, 2013, 02:05
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Jackie Chou
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Quote:
Originally Posted by wyldckat View Post
Hi Jackie,

My guess is that the surface is inside the mesh, which leads to it not being associated to existing boundary faces... because inside the mesh there are no boundary faces.

If I remember correctly, you're trying to re-assign patch names back to the interfaces between regions. Have you split the mesh into the separate regions?

Best regards,
Bruno
Hi, Bruno,

Thank you for the quick reply.You remember correctly. I have got the internal mesh and they are several regions, but i do not split them, I am going to re-assign patch names only for the outlets, like inlet and then outlet. It is just a box, flow in and then another outlet out. Because of some porous zones inside of the box, I have to make them several regions. But I do not split them up.

Actually, I tried to get back the internal boundary, some of them succeeds. If I only do for outlets and inlet, it is also not totally getting back the boundary .
do you think I should increase the tolerance ? Or must I split them up firstly?

Another strange thing is that when I finish snappyhexmesh and then
Use setSet to keep the needed regions, namely, delete the block. I get most of the needed mesh , but there is a small part which does not belong to my model. It is also not connected to my model. Do you know where it could come from? How can I avoid this part?

Thanks again! Look forward to your reply.

Morning!

Jackie
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Old   June 17, 2016, 10:28
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Derek Mitchell
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Here is a solution that removes the region and moves exposed cells to an existing patch e.g. myexistingpatch

use topoSetDict to select the wanted cellsets of the wanted regions in to a single cellset e.g. mywantedregionscellset and use
Code:
topoSet
subsetMesh -patch myexistingpatch  mywantedregionscellset -overwrite
splitMeshRegions -cellZones -overwrite
here is an example case where I took the tutorial snappyMultiRegionSimpleHeater
and then removed the region bottomAir and moved all the exposed internal faces to patch minY using the above technique. tested in OF3.0+.


Attached Files
File Type: zip snappyMultiRegionSimpleHeaterRemovingBottomAir.zip (86.2 KB, 0 views)
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Last edited by derekm; June 17, 2016 at 15:20.
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