Problem with quasi-2d axisymmetric mesh

Chrsty · May 6, 2011, 18:32

I have a 2-D mesh (Fluent mesh generated in ICEMCFD) and am attepting to use it as a quasi-2D case in CFX. The case is axisymmetric so I am using the advanced options in Import Mesh to override the 2d mesh and interpret it as axisymmetric. The mesh inports without any errors however the mesh contains wedges instead of prisms in some locations (see first pic). I tried to fix this by using the duplicate node checking option but this led to an error with invalid degenerate elements. I then tried using the option ignore invalid degenerate elements but this led to an error with "Unable to construct 3D region interfaces". Can someone point out what I am doing wrong or some other things I can try to get this to work? Any help would be much appreciated.

ghorrocks · May 7, 2011, 08:59

Make sure you have node merging off in CFX-Pre.

You may have to draw the mesh as a wedge in ICEM and take it into CFX-Pre as a 3D.

Chrsty · May 7, 2011, 09:27

Thank you for your quick reply Glen, your input is much appreciated.

Where exactly can I 'make sure you have node merging off in CFX-Pre'. I initially thought I was doing this by not using the 'duplicate node checking option' in the advanced mesh import options but that led to what you can see in the picture. I then presumed that CFX was merging nodes using a a default tolerance so tried using the 'duplicate node checking option' with both the default tolerance and varying the tolerance which resulted in the errors outlined in my previous post.

I was beginning to think I would have to go back to ICEM and model it as a 3D mesh there. I have quite a complex quad mesh, can I just rotationally extrude the mesh or do I need to delete the mesh, rotationally copy the blocking and remesh or do I need to delete everything bar the geometry rotationally copy that and start my blocking and meshing from scratch?

ghorrocks · May 8, 2011, 09:12

If you tried the duplicate node checking options then you found it. That is what I had in mind.

In ICEM it is straightforward to take a 2D mesh, extrude it around a wedge to make it a 2D axisymmetric model. You will have to manually recreate the boundary conditions (at least you had to last time I did it years ago).

May 6, 2011, 18:32	Problem with quasi-2d axisymmetric mesh	#1
Chrsty New Member Join Date: Aug 2010 Posts: 3 Rep Power: 16	I have a 2-D mesh (Fluent mesh generated in ICEMCFD) and am attepting to use it as a quasi-2D case in CFX. The case is axisymmetric so I am using the advanced options in Import Mesh to override the 2d mesh and interpret it as axisymmetric. The mesh inports without any errors however the mesh contains wedges instead of prisms in some locations (see first pic). I tried to fix this by using the duplicate node checking option but this led to an error with invalid degenerate elements. I then tried using the option ignore invalid degenerate elements but this led to an error with "Unable to construct 3D region interfaces". Can someone point out what I am doing wrong or some other things I can try to get this to work? Any help would be much appreciated.

May 7, 2011, 08:59		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	Make sure you have node merging off in CFX-Pre. You may have to draw the mesh as a wedge in ICEM and take it into CFX-Pre as a 3D. Chrsty likes this.

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May 7, 2011, 09:27		#3
Chrsty New Member Join Date: Aug 2010 Posts: 3 Rep Power: 16	Thank you for your quick reply Glen, your input is much appreciated. Where exactly can I 'make sure you have node merging off in CFX-Pre'. I initially thought I was doing this by not using the 'duplicate node checking option' in the advanced mesh import options but that led to what you can see in the picture. I then presumed that CFX was merging nodes using a a default tolerance so tried using the 'duplicate node checking option' with both the default tolerance and varying the tolerance which resulted in the errors outlined in my previous post. I was beginning to think I would have to go back to ICEM and model it as a 3D mesh there. I have quite a complex quad mesh, can I just rotationally extrude the mesh or do I need to delete the mesh, rotationally copy the blocking and remesh or do I need to delete everything bar the geometry rotationally copy that and start my blocking and meshing from scratch?

May 8, 2011, 09:12		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	If you tried the duplicate node checking options then you found it. That is what I had in mind. In ICEM it is straightforward to take a 2D mesh, extrude it around a wedge to make it a 2D axisymmetric model. You will have to manually recreate the boundary conditions (at least you had to last time I did it years ago).