Multi element wing 3-d problem: trailing edge resolution

sriram042000 · March 11, 2011, 13:53

Hi,
I tried running a 3-d case for a multi element wing set and these are the results I got. The streamlines don't look wonky but when you look at the contour plots, something is definitely not letting the boundary layer resolve. I have also attached a post processing plot of the wall alone(the wing) which shows how the meshing has chipped part of the trailing edges. How can I avoid that?

I spoke to some CFD profs in the university and they weren't sure of the problem either. Their suggestion was that since this is a wing with a trailing edge thickness( i.e, not a sharp t.e) the minimum mesh size may be more than that thickness. Has anybody else seen this problem before? If so, what is the solution?

The mesh has 15 million elements. Also, the CAD geometry was imported as IGES from solid works and was clean when seen in the DM.

Thanks.

chaman · March 13, 2011, 00:33

Quote:

Originally Posted by sriram042000

Hi,
I tried running a 3-d case for a multi element wing set and these are the results I got. The streamlines don't look wonky but when you look at the contour plots, something is definitely not letting the boundary layer resolve. I have also attached a post processing plot of the wall alone(the wing) which shows how the meshing has chipped part of the trailing edges. How can I avoid that?

I spoke to some CFD profs in the university and they weren't sure of the problem either. Their suggestion was that since this is a wing with a trailing edge thickness( i.e, not a sharp t.e) the minimum mesh size may be more than that thickness. Has anybody else seen this problem before? If so, what is the solution?

The mesh has 15 million elements. Also, the CAD geometry was imported as IGES from solid works and was clean when seen in the DM.

Thanks.

HI,
your mesh has 15 million elements... it is not shows the quality your mesh.
you have bad mesh around body, re-mesh surface on your body and then
do volume mesh

I have this problem before when the minimum mesh size be more than that trailing edge thickness ...

ghorrocks · March 13, 2011, 05:44

You do not appear to have inflation meshes. You are not going to get any useful results without a good inflation mesh.

The trailing edge problem is because it is equivalencing nodes through the wing thickness where it is thin. This can be a diabolical problem to fix. In ICEM you can declare thin cuts to handle this. CFX-Mesh is usually resistant to this sort of problem.

Did you mesh it in ICEM? Or in workbench using the patch independant mesher?

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March 13, 2011, 05:44		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You do not appear to have inflation meshes. You are not going to get any useful results without a good inflation mesh. The trailing edge problem is because it is equivalencing nodes through the wing thickness where it is thin. This can be a diabolical problem to fix. In ICEM you can declare thin cuts to handle this. CFX-Mesh is usually resistant to this sort of problem. Did you mesh it in ICEM? Or in workbench using the patch independant mesher?