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Chander August 17, 2011 11:41

Effective thermal conductivity in turbulent flow
 
I am simulating single phase incompressible turbulent flow using basic k-omega model in CFX 12. I want to know the effective thermal conductivity from the results at each point in fluid domain. Now
effective thermal conductivity = thermal conductivity of fluid + Cp * eddy viscosity/ turbulent Pr

eddy viscosity is listed as a variable in CFX post can be accessed. Where is the value of turbulent Pr listed? If I am thinking correctly, this is an empirical constant for the k-omega model but I could not find its value in the documentation.

Thanks for your help.

Best,
Chander

ghorrocks August 17, 2011 18:41

It is set in the turbulence model details in CFX-Pre. I think by default it is 0.7 but you should check this.

Chander August 17, 2011 19:24

Quote:

Originally Posted by ghorrocks (Post 320538)
It is set in the turbulence model details in CFX-Pre. I think by default it is 0.7 but you should check this.

I checked in CFX pre but I do not see any entry for turbulent Pr there.
Anywhere else I could look?

Also, is the way I am trying to account for turbulence in thermal conductivity ( the formula in my above post) correct?

ghorrocks August 17, 2011 19:30

In CFX-Pre, setting the domain: Fluid Models/Turbulence/Turbulence Flux Closure for Heat transfer/Turbulent Prandtl Number. Looks like the default for k-omega is 0.9.

Chander August 18, 2011 09:55

Quote:

Originally Posted by ghorrocks (Post 320552)
In CFX-Pre, setting the domain: Fluid Models/Turbulence/Turbulence Flux Closure for Heat transfer/Turbulent Prandtl Number. Looks like the default for k-omega is 0.9.

I could not see the option of '..Turbulence Flux Closure for Heat transfer/Turbulent Prandtl Number' in the domain settings. I am using version 12.1. Are you using a different version?


Also, the Ansys CFX support says that turbulent prandtl number is defined as sigma-omega and is equal to 2 as given in the cfx solver theory guide under k-omega model. But I dont see it among the options in CFX-Pre.

Does it mean it is hardcoded and not accesible in my version of 12.1?

ghorrocks August 18, 2011 18:45

I am on V13. Also you might need an advanced turbulence model license (or a full capability solver license) to access it.


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