Issue with transition models

k.vimalakanthan · April 21, 2011, 12:16

Hi guys,

Im trying to simulate a 2D flow around the S809 airfoil (see attached picture). Flow reynolds number is 2 million (2D grid with unity depth). Im using the SST gama theta transition model for my simulation, currently I have been faced with an unknown problem. A grid consisting of 1 million elements was used. The simulation was run for 5000 iterations (convergence history is attached). The turbulence intensity of 0.03% was used. Unusually the wall shear stress distribution (see attached picture) suggests a cross flow between the two ends of the wing (symmetry conditions). Because of this two different distribution of shear stress is obtained at the suction(top) surface. I was wondering if anyone else faced the same issue with the gama theta SST model. If so could you please tell me where I'm going wrong and please suggests a way to solve this problem.

Any help on this matter is greatly appreciated.

Thanks in advance

Screen shot 2011-04-21 at 16.07.22.png, Screen shot 2011-04-21 at 15.51.05.jpg

WallShear.jpg, TT.png

Mesh2.jpg

ghorrocks · April 26, 2011, 23:15

Looks like you problem is more to do with this FAQ:

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

April 21, 2011, 12:16	Issue with transition models	#1
k.vimalakanthan Member Kisorthman Vimalakanthan Join Date: Apr 2011 Posts: 49 Rep Power: 15	Hi guys, Im trying to simulate a 2D flow around the S809 airfoil (see attached picture). Flow reynolds number is 2 million (2D grid with unity depth). Im using the SST gama theta transition model for my simulation, currently I have been faced with an unknown problem. A grid consisting of 1 million elements was used. The simulation was run for 5000 iterations (convergence history is attached). The turbulence intensity of 0.03% was used. Unusually the wall shear stress distribution (see attached picture) suggests a cross flow between the two ends of the wing (symmetry conditions). Because of this two different distribution of shear stress is obtained at the suction(top) surface. I was wondering if anyone else faced the same issue with the gama theta SST model. If so could you please tell me where I'm going wrong and please suggests a way to solve this problem. Any help on this matter is greatly appreciated. Thanks in advance Screen shot 2011-04-21 at 16.07.22.png, Screen shot 2011-04-21 at 15.51.05.jpg WallShear.jpg, TT.png Mesh2.jpg Last edited by k.vimalakanthan; April 22, 2011 at 09:34. Reason: picture change

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April 26, 2011, 23:15		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	Looks like you problem is more to do with this FAQ: http://www.cfd-online.com/Wiki/Ansys...gence_criteria