CFX-11 vs CFX-13 SST Model

Zigainer · November 30, 2011, 06:13

Hey,

I'm simulating a two-pass-channel with rectangular geometry.
I've got some previous results with CFX-11 and SST Model. The previous simulation (done by a other person) compares different turbulence models for the same geometry. My CFX-13 results (also done with SST model) are different.
So does anybody know, what ANSYS changed in there turbulence models?
It kind of looks like the CFX-13 SST model uses some elements from CFX-11 SST cc model.
Hope you guys know a little bit more.

Far · December 1, 2011, 13:26

Well, I dont see any change in SST model

ghorrocks · December 1, 2011, 17:48

I suspect there have been some small changes in a few of the peripheral models (eg streamline curvature) and the numerics could be different. You would have to either troll through the release notes or contact CFX support to be sure.

Far · December 1, 2011, 18:04

I ran few cases on CFX 12 and 13 with SST model and same settings (e.g. same mesh, boundary conditions etc) and I didn't find any difference

ghorrocks · December 2, 2011, 00:46

For almost all cases you won't find a difference. It is only on rare cases that you will find a difference.

Far · December 2, 2011, 02:42

I would suggest to compare each and every term and constant factor in CFX theory guide of V 12 and 13

Zigainer · December 2, 2011, 03:18

Thanks guys. I compared the factor in theory guide and there are all the same. I was just wondering about my results (compared to a old study done by a stundent in 2010)

Far · December 2, 2011, 05:06

Mesh and other settings are same in your study and old resutls?

Zigainer · December 2, 2011, 05:14

Quote:

Originally Posted by Far

Mesh and other settings are same in your study and old resutls?

Not quite the same (I don't habe the old mesh). Problem is, that I am doing a conjugated calculation for a ribbed cooling-channel. The older thesis did only simulate the fluid with constant wall-temperature. My results are not very close to the experiment (different contour). The old thesis (turbulence model study) has almost the same contour with SST. But the old SST cc looks quite the same as my SST. And in the end my results for heat transfer are too good (Nu/Nu_0 is almost constantly 0.5 above experiment).

Far · December 2, 2011, 05:33

SST and SST-CC model are same except in some flow regions where CC model is activated (some triggering factor in production term). Therefore if your problem does not have that sort of region of flow then SST and SST-CC shall behave identically.

Zigainer · December 2, 2011, 05:40

Quote:

Originally Posted by Far

SST and SST-CC model are same except in some flow regions where CC model is activated (some triggering factor in production term). Therefore if your problem does not have that sort of region of flow then SST and SST-CC shall behave identically.

Thanks for your help. I probalbly have some of these regions because my channel is ribbed.
So I startet a SST-cc calculation, and then I'll see if there is a difference in CFX-13.

November 30, 2011, 06:13	CFX-11 vs CFX-13 SST Model	#1
Zigainer Senior Member Join Date: May 2011 Location: Germany Posts: 130 Rep Power: 15	Hey, I'm simulating a two-pass-channel with rectangular geometry. I've got some previous results with CFX-11 and SST Model. The previous simulation (done by a other person) compares different turbulence models for the same geometry. My CFX-13 results (also done with SST model) are different. So does anybody know, what ANSYS changed in there turbulence models? It kind of looks like the CFX-13 SST model uses some elements from CFX-11 SST cc model. Hope you guys know a little bit more.

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December 1, 2011, 13:26		#2
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Well, I dont see any change in SST model

December 1, 2011, 17:48		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	I suspect there have been some small changes in a few of the peripheral models (eg streamline curvature) and the numerics could be different. You would have to either troll through the release notes or contact CFX support to be sure.

December 1, 2011, 18:04		#4
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	I ran few cases on CFX 12 and 13 with SST model and same settings (e.g. same mesh, boundary conditions etc) and I didn't find any difference

December 2, 2011, 00:46		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	For almost all cases you won't find a difference. It is only on rare cases that you will find a difference.

December 2, 2011, 02:42		#6
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	I would suggest to compare each and every term and constant factor in CFX theory guide of V 12 and 13

December 2, 2011, 03:18		#7
Zigainer Senior Member Join Date: May 2011 Location: Germany Posts: 130 Rep Power: 15	Thanks guys. I compared the factor in theory guide and there are all the same. I was just wondering about my results (compared to a old study done by a stundent in 2010)

December 2, 2011, 05:06		#8
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Mesh and other settings are same in your study and old resutls?

December 2, 2011, 05:33		#10
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	SST and SST-CC model are same except in some flow regions where CC model is activated (some triggering factor in production term). Therefore if your problem does not have that sort of region of flow then SST and SST-CC shall behave identically.