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Old   June 27, 2001, 07:17
Default Turbulence Models.
  #1
Gavin Brady
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I have been asked to use a "Realizable k-eplsilon" model in my industrial project for my masters. Does anyone know what is the fundamental difference between this and the standard "k-eplsilon" model? All comments appreciated. Cheers.
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Old   June 27, 2001, 07:55
Default Re: Turbulence Models.
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sylvain
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Hello,

The name Realizable k-epsilon model is used by Fluent for the Shih, Zhu and Lumley evolution of the k-epsilon model. It refers to several NASA/ICOMP papers. The final and "really" realizable version of this model is describe in the following paper "Developments in Computational Modeling of the Turbulent Flows" - Tsan-Hsing Shih - NASA Contractor Report 198458 - ICOMP-96-04; CMOTT-96-03 - February 1996.

The main features of this model are the following :

- uu = 2/3*k - 2*c_nu*k^2/eps*dU/dx can NOT be negative since c_nu is no more a constant.

- the production term of the epsilon equation is equal to c_1*eps*S instead of c_eps_1*c_nu*k*S^2, where c_1 is NOT a constant.

This last item gives a better stability to the turbulence model.

Hope that helps,

Sylvain
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Old   July 14, 2001, 02:27
Default Re: Turbulence Models.
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Max
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simply speaking, realizable k-e models impose some conditions, usually derived based on some turbulence physics arguments, to prevent k and e (or some parameters derived from k and e) from going to wrong values...
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