- **OpenFOAM Running, Solving & CFD**
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- - **RealizableKE**
(*https://www.cfd-online.com/Forums/openfoam-solving/58744-realizableke.html*)

Sorry, but I can't find anywheSorry, but I can't find anywhere a default set of values for the compressible realizable k-epsilon model:
Cmu A0 C2 alphak alphaEps alphah can anybody help me? thanks |

From paper by Shih et al. (ComFrom paper by Shih et al. (Computers and Fluids Vol. 24, No. 3, pp. 227-238, 1995) it seems to be
realizableKECoeffs { Cmu Cmu [0 0 0 0 0 0 0] 0.09; A0 C1 [0 0 0 0 0 0 0] 4.0; C2 C2 [0 0 0 0 0 0 0] 1.92; alphak alphaK [0 0 0 0 0 0 0] 1.0; alphaEps alphaEps [0 0 0 0 0 0 0] 1.2; } /N |

Seems like there are some missSeems like there are some missing entries like alphah etc.
Does anybody know the realiableKECoeff ? I cannot find any references in OF? |

realizableKECoeffs
{
CmurealizableKECoeffs
{ Cmu Cmu [0 0 0 0 0 0 0] 0.09; A0 A0 [0 0 0 0 0 0 0] 4.04; C2 C2 [0 0 0 0 0 0 0] 1.92; alphak alphak [0 0 0 0 0 0 0] 1.0; alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923; } |

thanks Hrv, but with this setuthanks Hrv, but with this setup the following error occurs:
keyword alphah is undefined in dictionary " in turbulenceProperties::realizableKECoeffs" |

the coefficient alphah is usedthe coefficient alphah is used to evaluate the effective turbulent thermal diffusivity. (see realizableKE.h)
just add alphah alphah [0 0 0 0 0 0 0] 1; as in realizableKECoeffs { Cmu Cmu [0 0 0 0 0 0 0] 0.09; A0 A0 [0 0 0 0 0 0 0] 4.04; C2 C2 [0 0 0 0 0 0 0] 1.92; alphak alphak [0 0 0 0 0 0 0] 1.0; alphaEps alphaEps [0 0 0 0 0 0 0] 0.76923; alphah alphah [0 0 0 0 0 0 0] 1; } |

I have a question about the reI have a question about the relationship between the value of sigmaEps given by Shih (1.2) and the value of alphaEps given by Jasak (0.76923).
With these values alphaEps = 1 / (sigmaEps + 0.1), but where does the 0.1 come from? I have studied the equations in the Shih paper and realizable.C, but there is too much mathematical wizardry going on for me to fully understand it. Thank you. Sylvester |

Dear Foamers,
to clarify thDear Foamers,
to clarify the situation the following should be noted: OpenFOAM's implementation of the realizable k-e model does not strictly follow the paper of Shih et al. and the coefficients proposed in it: sigmaEps is 1.3 in OF (and hence 1/sigmaEps = alphaEps = 0.76923), whereas Shih et al. [1] propose sigmaEps = 1.20 (see Eqn. 28 of their paper). Furthermore, OF uses C2=1.92 whereas Shih et al. [1] use 1.9 (see table 2 of their paper). These two deviations may be errors or may be introduced by the programmers/users to be consistent with the standard k-e model. Also A0 is 4.0 in Shih et al. [1] and not 4.04 as proposed here. (However, the value of 4.04 is consistent with www.cfd-online.com/Wiki while the others are not). It seems that all equations are consistent with the paper of Shih et al. [1] except the fact, that OF uses (nut/sigmak+nu) and (nut/sigmaEps+nu) instead of (nut/sigmak) and (nut/sigmaEps) as in the paper of Shih et al. [1] respectively. This is of course a small effect and should not have any further consequences at high Re-number flows. I hope this clarifies the parameters of the OF realizableKE model and I would like to suggest to include a clarification in the next release of OF. Reference: [1]Tsan-Hsing Shih, William W. Liou, Aamir Shabbir, Zhigang Tang and Jiang Zhu. 1995. A New k-epsilon Eddy Viscosity Model for High Reynolds Number Turbulent Flows, Computers and Fluids 24. 227-238. |

Hi, foamers.
I have two question about realizable k-epsilon turbulent model. I included in RASProperties file the following coefficients (I found them in realizableKE.H):Code:
`realizableKECoeffs` Anyway, I obtain the following error: Code:
`Selecting incompressible transport model Newtonian` Thanks for your attention. |

It means I'm an idiot. The
realizableKE coefficients are correct, but I derived /0/epsilon from /0/omega (it was an 'old' case) and I forgot to edit the units too. |

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