One Mesh - Two Boundaries

karwendel · June 12, 2019, 15:46

Dear all,
is there a chance to apply 2 boundaries conditions to one mesh 2D region? For example I have got a round outlet but the flow is only allowed to flow through the upper semi-circle and the lower semi-circle is treated like a wall?

I want to avoid to use a know mesh. I was thinking about a user surface but don't know how to apply a boundary condition to it.

Thank you.

Opaque · June 12, 2019, 15:48

If you know it is a semi-circle, you must split the circle into two parts, then apply boundary conditions for each separately.

karwendel · June 12, 2019, 15:55

But I can I split the boundary somehow in CFX-Pre by a user-surface or do I need to come up with whole new mesh?

ghorrocks · June 12, 2019, 18:58

You need to do a new mesh.

Gert-Jan · June 13, 2019, 02:47

1) remesh the thing.
2) Don't know the source of the mesh, but you can try to import the mesh in ICEM, put the wall elements in a new part, export the mesh and you have what you want.
3) Alternative escape: draw a cube, mesh this as a solid block, import it into pre and position it as an immersed solid on your outlet to block the upper or lower part.
This is quick and dirty, and not very accurate, but might be a viable escape, if you have not other option left.

karwendel · June 13, 2019, 03:35

Thank you very much. Then I know what to do

June 12, 2019, 15:46	One Mesh - Two Boundaries	#1
karwendel New Member Michael Hopfinger Join Date: Mar 2017 Posts: 14 Rep Power: 9	Dear all, is there a chance to apply 2 boundaries conditions to one mesh 2D region? For example I have got a round outlet but the flow is only allowed to flow through the upper semi-circle and the lower semi-circle is treated like a wall? I want to avoid to use a know mesh. I was thinking about a user surface but don't know how to apply a boundary condition to it. Thank you.

June 12, 2019, 18:58		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,708 Rep Power: 143	You need to do a new mesh. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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June 12, 2019, 15:48		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,806 Rep Power: 32	If you know it is a semi-circle, you must split the circle into two parts, then apply boundary conditions for each separately.

June 12, 2019, 15:55		#3
karwendel New Member Michael Hopfinger Join Date: Mar 2017 Posts: 14 Rep Power: 9	But I can I split the boundary somehow in CFX-Pre by a user-surface or do I need to come up with whole new mesh?

June 13, 2019, 02:47		#5
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,831 Rep Power: 27	1) remesh the thing. 2) Don't know the source of the mesh, but you can try to import the mesh in ICEM, put the wall elements in a new part, export the mesh and you have what you want. 3) Alternative escape: draw a cube, mesh this as a solid block, import it into pre and position it as an immersed solid on your outlet to block the upper or lower part. This is quick and dirty, and not very accurate, but might be a viable escape, if you have not other option left.

June 13, 2019, 03:35		#6
karwendel New Member Michael Hopfinger Join Date: Mar 2017 Posts: 14 Rep Power: 9	Thank you very much. Then I know what to do