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Are user-defined sources density weighted?

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Old   October 14, 2009, 12:47
Default Are user-defined sources density weighted?
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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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Old   October 14, 2009, 15:11
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you don't have to include density in production term.
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Old   October 14, 2009, 15:25
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But it's included in the epsilon term? So,
source = Pk-rho*epsilon
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Old   October 14, 2009, 15:57
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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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