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why omega instead of epsilon in turbulence modeling

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Old   May 5, 2012, 09:14
Default why omega instead of epsilon in turbulence modeling
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Priyanshu Goyal
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Dear All,

I have a very basic doubt. Why there is a need to write the equation of omega instead of epsilon in turbulence modeling. Are there any advantages of omega equation which cannot be incorporated in epsilon equation.

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Old   May 5, 2012, 12:02
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Paolo Lampitella
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When you write the epsilon equation in terms of omega you get an equation which is different from the wilcox omega equation, due to the elimination of a term (proportional to grad_omega * grad_k). In the SST formulation of the k-omega model this term is not eliminated but dumped to the walls.

This additional term, which is the only difference among the two and justifies the generally better results for the SST model, is not explicitly visible in the epsilon equation, hence the choice. In theory, an equivalent term could be subtracted from the epsilon equation but this term would imply the gradient of an epsilon/k function which is much more cumbersome to discretize (besides the accuracy issues).

I am not aware of any other reason, still there could be additional ones
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Last edited by sbaffini; May 5, 2012 at 12:09. Reason: Accidentally pushed the quick reply button
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