Boussinesq eddy viscosity assumption

siw · February 17, 2011, 10:25

Hi,

The Boussinesq eddy viscosity assumption is given at:

http://www.cfd-online.com/Wiki/Bouss...ity_assumption

where the Reynolds stress tensor contains the fluctuating components of the velocity components when they are Reynolds decomposed (http://www.cfd-online.com/Wiki/Reynolds_averaging).

My questions are:

1. Are the terms on the Right-Hand Side of the equation the instantaneous velocity, density and kinetic energy?

2. Would the eddy viscosity assumption be different if the Reynolds stress tensor contained fluctuating components of the velocity components when they are Favre decomposed (http://www.cfd-online.com/Wiki/Favre_averaging)?

I cannot find these answers anywhere.

Thanks

pavitran · February 17, 2011, 10:58

They are average values not instantaneous.
I guess the eddy viscosity assumption may not be different when the are favre decomposed.

siw · February 17, 2011, 13:30

Thanks for the reply.

Please can anyone explain the case for question 2?

February 17, 2011, 10:25	Boussinesq eddy viscosity assumption	#1
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 739 Rep Power: 26	Hi, The Boussinesq eddy viscosity assumption is given at: http://www.cfd-online.com/Wiki/Bouss...ity_assumption where the Reynolds stress tensor contains the fluctuating components of the velocity components when they are Reynolds decomposed (http://www.cfd-online.com/Wiki/Reynolds_averaging). My questions are: 1. Are the terms on the Right-Hand Side of the equation the instantaneous velocity, density and kinetic energy? 2. Would the eddy viscosity assumption be different if the Reynolds stress tensor contained fluctuating components of the velocity components when they are Favre decomposed (http://www.cfd-online.com/Wiki/Favre_averaging)? I cannot find these answers anywhere. Thanks

February 17, 2011, 10:58	Hi	#2
pavitran Member Dynampally Pavitran Join Date: Mar 2010 Location: India Posts: 74 Rep Power: 16	They are average values not instantaneous. I guess the eddy viscosity assumption may not be different when the are favre decomposed.

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February 17, 2011, 13:30		#3
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 739 Rep Power: 26	Thanks for the reply. Please can anyone explain the case for question 2?