# Mixed cell zone remeshing in FLUENT 12

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April 19, 2010, 10:10
Mixed cell zone remeshing in FLUENT 12
#1
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Chester
Join Date: Feb 2010
Posts: 24
Rep Power: 7
Hi all,

I can read this from the User's Guide :
Quote:
 The available remeshing methods in ANSYS FLUENT work for triangulartetrahedral zones and mixed zones where the non-triangular/tetrahedral elements are skipped.
It doesn't seems to work for me. I have two zones :
1/ Hexahedral zone (sweep mesh);
2/ Mixed cell zone (tetrahedral conforming mesh);

So in the mixed cell zone I have pyramids that make transition from HEX to TET elements. The issue is that when the interface between the two zones is moving (compressing the mixed cell zone) I have negative volumes appearing.

I know that I can make wedges instead of hex, make hex with non-conformal interface, make a transition layer with pyramids only etc.. But I want to know why it doesn't work like it is written in the manual.

 April 23, 2010, 03:25 #2 Member   李逾 Join Date: Mar 2010 Posts: 65 Rep Power: 7 could you tell me why must building a transition zone between tet and hex?

April 23, 2010, 05:33
#3
New Member

Chester
Join Date: Feb 2010
Posts: 24
Rep Power: 7
Quote:
 Originally Posted by yubaibai88 could you tell me why must building a transition zone between tet and hex?
Because when you move from an HEX zone to a TET zone, the elements that are making the transition are pyramids. But pyramids are not remeshed by the fluent remeshing algorithm hence they can cause troubles.

 April 23, 2010, 08:59 #4 Member   李逾 Join Date: Mar 2010 Posts: 65 Rep Power: 7 where are the pyramids come?

April 23, 2010, 09:43
#5
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Chester
Join Date: Feb 2010
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Quote:
 Originally Posted by yubaibai88 where are the pyramids come?
From the meshing process. It has to close an elementary volume with 1 rectangular face (coming from the HEX mesh) and 3 triangular faces (coming from the TET mesh) i.e. pyramidal element.

April 23, 2010, 10:19
#6
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Join Date: Mar 2010
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Quote:
 Originally Posted by ChesterP From the meshing process. It has to close an elementary volume with 1 rectangular face (coming from the HEX mesh) and 3 triangular faces (coming from the TET mesh) i.e. pyramidal element.
I generate the mesh by creating two adjacent zones in which one is tet while the other is hex.set interface as the boundary condition.no pyramid appears.then import the .msh into fluent.creat nonconformal interface.although mesh motion can perform,grid check failed.
how did you model it

November 1, 2011, 07:53
#7
Member

stb
Join Date: Sep 2009
Posts: 35
Rep Power: 7
Quote:
 Originally Posted by ChesterP Because when you move from an HEX zone to a TET zone, the elements that are making the transition are pyramids. But pyramids are not remeshed by the fluent remeshing algorithm hence they can cause troubles.
I do not think pyramids will cause the problem. they will move according to airfoil zone ,wtihout remeshing and distortion.

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