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-   -   Are user-defined sources density weighted? (http://www.cfd-online.com/Forums/fluent/69186-user-defined-sources-density-weighted.html)

tstorm October 14, 2009 12:47

Are user-defined sources density weighted?
 
Hi all,

Does FLUENT require that user-defined sources be density weighted? For example, the k source is Pk-epsilon. Would that be defined in a UDF as

source = Pk-epsilon

or

source = C_R(c,t)*(Pk-epsilon)

?

Thanks!

tez October 14, 2009 15:11

you don't have to include density in production term.

tstorm October 14, 2009 15:25

But it's included in the epsilon term? So,
source = Pk-rho*epsilon

tez October 14, 2009 15:57

Yes it is. I suggest you to go through the FLUENT Manual "Turbulence Modeling" chapter and look for k-epsilon or k-omega model to be clear. If you simply balance the units of these terms you will understand. "D(rho*k)/Dt" has the same dimension as "mu_t*S*S". Good luck.


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