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adam2008 March 18, 2011 14:38

questions about GGI interface overlap
 
hi,
I have a question about GGI interface overlap. CFX experts please help.
I have two surfaces (one solid surface and one fluid boundary surface) I want to couple as interface in CFX in a conjugate simulation for heat transfer. For some reasons, two surfaces are offset by 0.016 inch although they have same geometry. Sorry I can't move meshes
No surprise, the current simulation indicates "non-overlapping area fractions=1.0" on both sides, and there is no heat flux across interface. I read CFX help a bit and found out there are some "Experts parameters" (ggi permit no intersection, ggi separation factor etc)that may help. However, I tested couple cases and they looked not as I expected.
Can someone give an answer what I can do on this?

Thanks a lot

joey2007 March 18, 2011 15:42

Yes, you can. CFX-Pre has a feature to translate meshes. Move one of your meshes by your offset.

adam2008 March 18, 2011 16:48

hi, thanks
but i guess I can't translate mesh. My simulation is: a highly complicated metal body coated with ceramic layer (0.016" thickness") and fluid flow passes around this solid. And we want to investigate the heat transfer inside metal and among metal, ceramic and fluid.
So I generated meshes for both metal and fluid domain using the same geometry surfaces. For ceramic layer, I extruded the solid surface meshes along their local normal outwards directions by 0.016" with several layers. Then I setup the interface between metal, ceramic and fluid. Specifically, the ceramic surface is exposed to fluid flow and there should be an interface between ceramic surface and fluid flow boundary. However, there is a 0.016" offset along normal directions between them, so CFX gives information of "non-overlapping area fraction=1" which leads to adiabatic condition (or no heat trans passing).

I guess I can't offset mesh. Can I do something to overcome this by forcing CFX couple those two surfaces? I don't want to generate new meshes (also very hard) based on the actually geometry formed by ceramic layer surfaces.

Thanks a lot!!!!!!!


Quote:

Originally Posted by joey2007 (Post 300098)
Yes, you can. CFX-Pre has a feature to translate meshes. Move one of your meshes by your offset.


ghorrocks March 20, 2011 22:08

You can set the GGI intersect controls in the interface panel. You should be able to increase the search distance so it can find matches over the gap. But if you make the distance too large it will start to find spurious matches so be careful.


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