Turbulence Schmidt Number for AV

Scott Nordsen · February 26, 2010, 10:08

What is the Turbulence Schmidt Number used for the diffusive term for additional variable transport equations? I expect it is 2 for k-w, but what if a k-eps is enabled where the Sc,t is different for the equations?

Background:
I am using additional variables (AVs) for a turbulence model.
As a test, I implement k-w model for a mixing layer.
For a first step, I am setting source terms based on CFX k and w.
Thus, the k and AV k equations should have the same source terms.
I expect that my AV k will be pretty close to CFX k. However, there are differences.
For this problem this can only be the diffusive term

Thanks

John · February 26, 2010, 10:31

As I recall, the default Turbulence Schmidt Number for species transport equation is 0.9.

Scott Nordsen · February 26, 2010, 12:10

Thanks that seems to have done it

Next question is how to change? What if no heat transfer option is set?

John · February 26, 2010, 18:21

TURBULENT FLUX CLOSURE:
Option = Eddy Diffusivity
Turbulent Schmidt Number = ??
END

Scott Nordsen · March 12, 2010, 15:22

I was wondering if there are other options for Option = ...

I would like to have a different turbulent diffusivity for the scalar equations than the momentum equations.

I have tried doing this by having a fancier function for the kinematic viscosity setting at the Domain Level.

However, it seems to be more restrictive on the variables being passed than say at the Subdomain level for the source terms.

February 26, 2010, 10:08	Turbulence Schmidt Number for AV	#1
Scott Nordsen New Member Join Date: Jun 2009 Posts: 13 Rep Power: 17	What is the Turbulence Schmidt Number used for the diffusive term for additional variable transport equations? I expect it is 2 for k-w, but what if a k-eps is enabled where the Sc,t is different for the equations? Background: I am using additional variables (AVs) for a turbulence model. As a test, I implement k-w model for a mixing layer. For a first step, I am setting source terms based on CFX k and w. Thus, the k and AV k equations should have the same source terms. I expect that my AV k will be pretty close to CFX k. However, there are differences. For this problem this can only be the diffusive term Thanks

February 26, 2010, 12:10		#3
Scott Nordsen New Member Join Date: Jun 2009 Posts: 13 Rep Power: 17	Thanks that seems to have done it Next question is how to change? What if no heat transfer option is set? Last edited by Scott Nordsen; February 26, 2010 at 15:43.

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February 26, 2010, 10:31		#2
John Member Join Date: Mar 2009 Posts: 49 Rep Power: 17	As I recall, the default Turbulence Schmidt Number for species transport equation is 0.9.

February 26, 2010, 18:21		#4
John Member Join Date: Mar 2009 Posts: 49 Rep Power: 17	TURBULENT FLUX CLOSURE: Option = Eddy Diffusivity Turbulent Schmidt Number = ?? END

March 12, 2010, 15:22		#5
Scott Nordsen New Member Join Date: Jun 2009 Posts: 13 Rep Power: 17	I was wondering if there are other options for Option = ... I would like to have a different turbulent diffusivity for the scalar equations than the momentum equations. I have tried doing this by having a fancier function for the kinematic viscosity setting at the Domain Level. However, it seems to be more restrictive on the variables being passed than say at the Subdomain level for the source terms.