Reynolds Stress Models for bluff body flows

siw · March 4, 2016, 05:29

Hi,

It is known that RANS linear eddy viscosity models; e.g. k-epsilon and k-omega based models, can have difficulty accurately predicting bluff body flows and that hybrid RANS-LES are preferred, see the ANSYS SRS Guide. However, for those of us that lack the computational resources to run hybrid RANS-LES models has it been shown that Reynolds Stress Models give more accurate prediction that RANS EVM models for bluff body flows? I've read that often EVM and RSM give very similar results and that it's not worth solving the extra RSM equations which are tougher to converge.

Thanks

ghorrocks · March 4, 2016, 06:58

In my experience RSM does not give much better results than 2 eqn models for bluff body flows. Where RSM makes a big difference is in rotating flows. But really you should try this for yourself and compare a k-e, SST, RSM and RANS-LES model and see the difference. If you don't have enough computer resources to do a RANS-LES model then simplify the model. Things like the Ahmed body has lots of published data and is simple enough that hopefully you can model it, even with RANS-LES.

March 4, 2016, 05:29	Reynolds Stress Models for bluff body flows	#1
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 742 Rep Power: 26	Hi, It is known that RANS linear eddy viscosity models; e.g. k-epsilon and k-omega based models, can have difficulty accurately predicting bluff body flows and that hybrid RANS-LES are preferred, see the ANSYS SRS Guide. However, for those of us that lack the computational resources to run hybrid RANS-LES models has it been shown that Reynolds Stress Models give more accurate prediction that RANS EVM models for bluff body flows? I've read that often EVM and RSM give very similar results and that it's not worth solving the extra RSM equations which are tougher to converge. Thanks

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March 4, 2016, 06:58		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	In my experience RSM does not give much better results than 2 eqn models for bluff body flows. Where RSM makes a big difference is in rotating flows. But really you should try this for yourself and compare a k-e, SST, RSM and RANS-LES model and see the difference. If you don't have enough computer resources to do a RANS-LES model then simplify the model. Things like the Ahmed body has lots of published data and is simple enough that hopefully you can model it, even with RANS-LES.