Floating point exception using RSM model

Jorg · November 20, 2012, 22:19

Hi, i'm trying to simulate a Circulation control airfoil using the Reinolds Stress Model but I have no experience with it; could anybody giveme some guidelines to get my simulation running?

RodriguezFatz · November 21, 2012, 03:54

Does your simulation converge with some less complex turbulence model (k-epsilon...)?
PS: RSM behaves like a diva...

Jorg · November 21, 2012, 18:14

Yes, it converges and behaves well when using k-omega or Spalart Almaras. I think i'm gonna need a very precise setup of the RSM inputs....

RodriguezFatz · November 22, 2012, 05:22

Hey, I am no expert in RSM, but I have a little experience just by trying different turbulence models: In my cases (2d, axisymmetric) the RSM always needed much more cells to work than all other models. Also, I had a few cases, when I never got the RSM working. In your case, I would start by trying to get reasonable values for the RSM boundary conditions at the inlet. If this doesn't work, you could refine your mesh to some unimaginably superb degree and see if that works...

Far · November 22, 2012, 08:23

It requires higher mesh quality specially cell aspect ratio (~10 or less)

See this thread for details http://www.cfd-online.com/Forums/cfx...nvergence.html

Jorg · November 23, 2012, 12:39

thanks for your help, i'll try to get higher mesh resolution and let's hope it works. Im concerned about the amount of elements i'll have to define in the flow direction of the boundary layer region to achieve such AR values...

November 20, 2012, 22:19	Floating point exception using RSM model	#1
Jorg New Member Jorge Tamayo Join Date: Jul 2012 Location: Delft, Netherlands Posts: 16 Rep Power: 13	Hi, i'm trying to simulate a Circulation control airfoil using the Reinolds Stress Model but I have no experience with it; could anybody giveme some guidelines to get my simulation running?

November 22, 2012, 08:23		#5
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	It requires higher mesh quality specially cell aspect ratio (~10 or less) See this thread for details http://www.cfd-online.com/Forums/cfx...nvergence.html Last edited by Far; November 22, 2012 at 08:43.

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November 21, 2012, 03:54		#2
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	Does your simulation converge with some less complex turbulence model (k-epsilon...)? PS: RSM behaves like a diva...

November 21, 2012, 18:14		#3
Jorg New Member Jorge Tamayo Join Date: Jul 2012 Location: Delft, Netherlands Posts: 16 Rep Power: 13	Yes, it converges and behaves well when using k-omega or Spalart Almaras. I think i'm gonna need a very precise setup of the RSM inputs....

November 22, 2012, 05:22		#4
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	Hey, I am no expert in RSM, but I have a little experience just by trying different turbulence models: In my cases (2d, axisymmetric) the RSM always needed much more cells to work than all other models. Also, I had a few cases, when I never got the RSM working. In your case, I would start by trying to get reasonable values for the RSM boundary conditions at the inlet. If this doesn't work, you could refine your mesh to some unimaginably superb degree and see if that works...

November 23, 2012, 12:39		#6
Jorg New Member Jorge Tamayo Join Date: Jul 2012 Location: Delft, Netherlands Posts: 16 Rep Power: 13	thanks for your help, i'll try to get higher mesh resolution and let's hope it works. Im concerned about the amount of elements i'll have to define in the flow direction of the boundary layer region to achieve such AR values...