turbulence flux closure for heat transfer

alinik · April 29, 2013, 15:39

Guys,

I am looking for some documentation regarding "anisotropic diffusion" model for turbulence flux closure for heat transfer in CFX. By default CFX uses "eddy diffusivity" model to correlate the reynolds heat flux to reynolds stress. This "anisotropic diffusion" model is available only for some of the turbulence models and I could not find any mathematical description of this model, not even in CFX documentation. Does any body know about these formulations?

Thanks

ghorrocks · April 29, 2013, 19:05

Do you mean Reynolds Stress Models, and the related Algebraic Stress models? These are the only turbulence models in CFX which support anisotropic turbulence. The derivation of these models is in the documentation, and if that is not good enough it is covered in any reasonable CFD textbook.

alinik · April 29, 2013, 19:13

No
I did not mean that, I am familiar with the turbulence models. I want to know what closure CFX uses for heat transfer or better to say "Reynolds flux". By default it uses eddy diffusivity model but for some turbulence models like BSL, there is another option available and that is "anisotropic diffusion". I would like to know more about that. I could not find anything in any documentations

ghorrocks · April 30, 2013, 19:31

I am not familiar with the option you refer to. To the best of my knowledge the heat equation just uses the Prandtl number to have a dissipation proportional to the turbulent viscous dissipation. I am not aware of any anisotropic options for this.

April 29, 2013, 15:39	turbulence flux closure for heat transfer	#1
alinik Senior Member ali Join Date: Oct 2009 Posts: 318 Rep Power: 17	Guys, I am looking for some documentation regarding "anisotropic diffusion" model for turbulence flux closure for heat transfer in CFX. By default CFX uses "eddy diffusivity" model to correlate the reynolds heat flux to reynolds stress. This "anisotropic diffusion" model is available only for some of the turbulence models and I could not find any mathematical description of this model, not even in CFX documentation. Does any body know about these formulations? Thanks

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April 29, 2013, 19:05		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Do you mean Reynolds Stress Models, and the related Algebraic Stress models? These are the only turbulence models in CFX which support anisotropic turbulence. The derivation of these models is in the documentation, and if that is not good enough it is covered in any reasonable CFD textbook.

April 29, 2013, 19:13		#3
alinik Senior Member ali Join Date: Oct 2009 Posts: 318 Rep Power: 17	No I did not mean that, I am familiar with the turbulence models. I want to know what closure CFX uses for heat transfer or better to say "Reynolds flux". By default it uses eddy diffusivity model but for some turbulence models like BSL, there is another option available and that is "anisotropic diffusion". I would like to know more about that. I could not find anything in any documentations

April 30, 2013, 19:31		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I am not familiar with the option you refer to. To the best of my knowledge the heat equation just uses the Prandtl number to have a dissipation proportional to the turbulent viscous dissipation. I am not aware of any anisotropic options for this.