Are user-defined sources density weighted?

tstorm · October 14, 2009, 13:47

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, 16:11

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

tstorm · October 14, 2009, 16:25

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

tez · October 14, 2009, 16:57

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.

October 14, 2009, 13:47	Are user-defined sources density weighted?	#1
tstorm Member Join Date: Apr 2009 Posts: 78 Rep Power: 17	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!

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October 14, 2009, 16:11		#2
tez New Member Tez Join Date: Oct 2009 Posts: 12 Rep Power: 17	you don't have to include density in production term.

October 14, 2009, 16:25		#3
tstorm Member Join Date: Apr 2009 Posts: 78 Rep Power: 17	But it's included in the epsilon term? So, source = Pk-rho*epsilon

October 14, 2009, 16:57		#4
tez New Member Tez Join Date: Oct 2009 Posts: 12 Rep Power: 17	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(rhok)/Dt" has the same dimension as "mu_tS*S". Good luck.