[mesh manipulation] How to separate frontAndBack

xuegy · January 26, 2021, 00:20

Hello all,

I have a 2D mesh from fluent. When I run fluentMeshToFoam, it is automatically converted to a single layer 3D mesh. The front and back planes are combined in a single patch named "frontAndBackPlanes".
There is a tutorial that splits the boundary patch: patch splitting for different boundary conditions However, since "front" and "back" patches share the same cell, this trick doesn't work.
I know that the ultimate solution is to make a single-layer 3D mesh in fluent but is there any workaround to do it within OpenFOAM?

Thanks!

simrego · January 26, 2021, 10:51

Hi!

Maybe it is a silly question, but why do you need to split it? 2D mesh -> front and back are empty, and you will need the same BCs there.
Also you shouldn't evaluate anything there so I think there is no reason for that.

BTW: check the topoSet and createPatch utlities.

xuegy · January 26, 2021, 11:42

Quote:

Originally Posted by simrego

Hi!

Maybe it is a silly question, but why do you need to split it? 2D mesh -> front and back are empty, and you will need the same BCs there.
Also you shouldn't evaluate anything there so I think there is no reason for that.

BTW: check the topoSet and createPatch utlities.

I need to use extrudeMesh to generate a 3D pipe from the cross-section. That’s why I want a separate face.
Or is there anyway to get a 2D face patch from Fluent directly?

simrego · January 26, 2021, 11:53

Well. Then it would be nicer to do it with blockMesh.
As I know you can't do it. So it this case I would go with topoSet+createPatch and extrude that patch.
Or simply do it in fluent which is the easiest way.

And as you originally asked:
"is there any workaround to do it within OpenFOAM?"
Yes, there is a workaround for nearly everything in OpenFOAM, but in the worst case you have to code a little.

January 26, 2021, 00:20	How to separate frontAndBack	#1
xuegy Senior Member Join Date: Jun 2016 Posts: 102 Rep Power: 10	Hello all, I have a 2D mesh from fluent. When I run fluentMeshToFoam, it is automatically converted to a single layer 3D mesh. The front and back planes are combined in a single patch named "frontAndBackPlanes". There is a tutorial that splits the boundary patch: patch splitting for different boundary conditions However, since "front" and "back" patches share the same cell, this trick doesn't work. I know that the ultimate solution is to make a single-layer 3D mesh in fluent but is there any workaround to do it within OpenFOAM? Thanks!

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January 26, 2021, 10:51		#2
simrego Senior Member anonymous Join Date: Jan 2016 Posts: 416 Rep Power: 14	Hi! Maybe it is a silly question, but why do you need to split it? 2D mesh -> front and back are empty, and you will need the same BCs there. Also you shouldn't evaluate anything there so I think there is no reason for that. BTW: check the topoSet and createPatch utlities.

January 26, 2021, 11:53		#4
simrego Senior Member anonymous Join Date: Jan 2016 Posts: 416 Rep Power: 14	Well. Then it would be nicer to do it with blockMesh. As I know you can't do it. So it this case I would go with topoSet+createPatch and extrude that patch. Or simply do it in fluent which is the easiest way. And as you originally asked: "is there any workaround to do it within OpenFOAM?" Yes, there is a workaround for nearly everything in OpenFOAM, but in the worst case you have to code a little.