create patches out of a patch with two parallel surfaces

Rebecca513 · October 4, 2011, 13:01

Dear all,

I have a patch with two parallel surfaces, and I need to split them into two separate patches as they will have different boundary conditions.

Can anyone tell me how to do that?

Thank you for your help!

Best,
hang

Rebecca513 · October 4, 2011, 13:06

Also, they are not cyclic, but flat. Thank you~

Phicau · October 4, 2011, 13:28

Hi

just a slight guess, but you may start again from blockMeshDict by difining them as separate patches. Or you can try "autoPatch 90" (you can choose a different angle, depending on your needs) and renaming patches on "./constant/polyMesh/boundary" file.

Hope it helps

Rebecca513 · October 4, 2011, 13:42

Hi Pablo,

Thank you for your reply.

The mesh was imported, and it is reconstruction from CT images, so I don't have a blockMeshDict.

My understanding, please correct me if I am wrong, is that autopatch works on the whole region, not allowing me to specify the patch. Also, the surfaces are not perfectly flat, the angles between any two surfaces are not the same, varying around 90. Or I should say that it is a deformed box. I tried to run the autoPatch on it. It generates about 200 new patches.... really frustrating

Phicau · October 5, 2011, 04:32

Yes, quite annoying, certainly.

Try varying the 90 supplied to autoPatch to reduce the resultant number of patches.

If this still does not work take a look at the mesh manipulation tools of OpenFOAM:
http://www.openfoam.com/features/mesh-manipulation.php
I guess you can make your split operation with the correct combination of them.

Rebecca513 · October 5, 2011, 10:34

Thank you!

It turned out that I could use faceset and createPatch to get two new patches out of the original one. In this way, I have more control over how many patches to generate.

Best,

Hang

songzhe · March 15, 2013, 17:14

Hi Hang

Could you please tell me how to use face set and createPatch to get new patches?

I use construct from face set in creatPatch, and use setSet to generate the face set. But I don't know how to specify in setSet dict.

My understanding is, for example, if you have a whole patch and want to split it into 2, you need to get a face set in one part of the whole patch, from which you want to get one your sub patches, and also for the other part of the whole patch.

# Create face sets
faceSet sideFaces1 new boxToFace (-0.00001 -0.00001 -1) (0.10001 0.00001 1)
faceSet sideFaces2 new boxToFace ( 0.09999 -0.00001 -1) (0.10001 0.05001 1)
faceSet sideFaces3 new boxToFace (-0.00001 0.04999 -1) (1.00001 0.05001 1)
faceSet sideFaces4 new boxToFace (-0.00001 -0.00001 -1) (0.00001 0.05001 1)

This is what I found in tutorial about how to set up in setSet. I guess the faces you want can be obtained by specifying the face centre located in the region specified in boxToFace. I am confused if you have a flat wall as a patch so all the faces are located in a plane, and all the face centres are also in a plane. So you just specify the region of boxToFace as a plane?

Thanks in advance
Songzhe

October 4, 2011, 13:01	create patches out of a patch with two parallel surfaces	#1
Rebecca513 Member HD Join Date: Jul 2011 Posts: 56 Rep Power: 15	Dear all, I have a patch with two parallel surfaces, and I need to split them into two separate patches as they will have different boundary conditions. Can anyone tell me how to do that? Thank you for your help! Best, hang

October 4, 2011, 13:42		#4
Rebecca513 Member HD Join Date: Jul 2011 Posts: 56 Rep Power: 15	Hi Pablo, Thank you for your reply. The mesh was imported, and it is reconstruction from CT images, so I don't have a blockMeshDict. My understanding, please correct me if I am wrong, is that autopatch works on the whole region, not allowing me to specify the patch. Also, the surfaces are not perfectly flat, the angles between any two surfaces are not the same, varying around 90. Or I should say that it is a deformed box. I tried to run the autoPatch on it. It generates about 200 new patches.... really frustrating Last edited by Rebecca513; October 4, 2011 at 13:58.

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October 4, 2011, 13:06		#2
Rebecca513 Member HD Join Date: Jul 2011 Posts: 56 Rep Power: 15	Also, they are not cyclic, but flat. Thank you~

October 4, 2011, 13:28		#3
Phicau Senior Member Pablo Higuera Join Date: Jan 2011 Location: Auckland Posts: 627 Rep Power: 19	Hi just a slight guess, but you may start again from blockMeshDict by difining them as separate patches. Or you can try "autoPatch 90" (you can choose a different angle, depending on your needs) and renaming patches on "./constant/polyMesh/boundary" file. Hope it helps

October 5, 2011, 04:32		#5
Phicau Senior Member Pablo Higuera Join Date: Jan 2011 Location: Auckland Posts: 627 Rep Power: 19	Yes, quite annoying, certainly. Try varying the 90 supplied to autoPatch to reduce the resultant number of patches. If this still does not work take a look at the mesh manipulation tools of OpenFOAM: http://www.openfoam.com/features/mesh-manipulation.php I guess you can make your split operation with the correct combination of them.

October 5, 2011, 10:34		#6
Rebecca513 Member HD Join Date: Jul 2011 Posts: 56 Rep Power: 15	Thank you! It turned out that I could use faceset and createPatch to get two new patches out of the original one. In this way, I have more control over how many patches to generate. Best, Hang

March 15, 2013, 17:14		#7
songzhe New Member Join Date: Mar 2013 Posts: 1 Rep Power: 0	Hi Hang Could you please tell me how to use face set and createPatch to get new patches? I use construct from face set in creatPatch, and use setSet to generate the face set. But I don't know how to specify in setSet dict. My understanding is, for example, if you have a whole patch and want to split it into 2, you need to get a face set in one part of the whole patch, from which you want to get one your sub patches, and also for the other part of the whole patch. # Create face sets faceSet sideFaces1 new boxToFace (-0.00001 -0.00001 -1) (0.10001 0.00001 1) faceSet sideFaces2 new boxToFace ( 0.09999 -0.00001 -1) (0.10001 0.05001 1) faceSet sideFaces3 new boxToFace (-0.00001 0.04999 -1) (1.00001 0.05001 1) faceSet sideFaces4 new boxToFace (-0.00001 -0.00001 -1) (0.00001 0.05001 1) This is what I found in tutorial about how to set up in setSet. I guess the faces you want can be obtained by specifying the face centre located in the region specified in boxToFace. I am confused if you have a flat wall as a patch so all the faces are located in a plane, and all the face centres are also in a plane. So you just specify the region of boxToFace as a plane? Thanks in advance Songzhe