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November 7, 2005, 05:11 |
Sorry, but I can't find anywhe
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#1 |
New Member
Canelli Claudio
Join Date: Mar 2009
Location: Genoa, Italy
Posts: 11
Rep Power: 17 |
Sorry, 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 |
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November 11, 2005, 03:41 |
From paper by Shih et al. (Com
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#2 |
Member
Niklas Wikstrom
Join Date: Mar 2009
Posts: 86
Rep Power: 17 |
From 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 |
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August 14, 2006, 11:49 |
Seems like there are some miss
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#3 |
Member
stefan
Join Date: Mar 2009
Posts: 96
Rep Power: 17 |
Seems like there are some missing entries like alphah etc.
Does anybody know the realiableKECoeff ? I cannot find any references in OF? |
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August 14, 2006, 11:51 |
realizableKECoeffs
{
Cmu
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#4 |
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,905
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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; }
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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August 14, 2006, 11:56 |
thanks Hrv, but with this setu
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#5 |
Member
stefan
Join Date: Mar 2009
Posts: 96
Rep Power: 17 |
thanks Hrv, but with this setup the following error occurs:
keyword alphah is undefined in dictionary " in turbulenceProperties::realizableKECoeffs" |
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August 14, 2006, 12:40 |
the coefficient alphah is used
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#6 |
Member
Pierre Le Fur
Join Date: Mar 2009
Location: UK
Posts: 60
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the 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; } |
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August 29, 2007, 03:13 |
I have a question about the re
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#7 |
Member
Roland
Join Date: Mar 2009
Location: Netherlands
Posts: 92
Rep Power: 17 |
I 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 |
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July 12, 2008, 12:13 |
Dear Foamers,
to clarify th
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#8 |
Member
Stefan Radl
Join Date: Mar 2009
Location: Graz, Austria
Posts: 82
Rep Power: 18 |
Dear 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. |
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March 28, 2011, 16:09 |
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#9 |
Senior Member
Join Date: Feb 2010
Posts: 213
Rep Power: 17 |
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 { Cmu 0.09; A0 4.0; C2 1.9; alphak 1.0; alphaEps 0.833333; alphah 1.0; // only for compressible } Anyway, I obtain the following error: Code:
Selecting incompressible transport model Newtonian Selecting RAS turbulence model realizableKE [0] [0] [0] LHS and RHS of + have different dimensions dimensions : [0 0 -1 0 0 0 0] + [0 2 -3 0 0 0 0] [0] [0] [0] From function operator+(const dimensionSet& ds1, const dimensionSet& ds2) [0] in file dimensionSet/dimensionSet.C at line 403. [0] FOAM parallel run aborting Thanks for your attention. |
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March 31, 2011, 03:45 |
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#10 |
Senior Member
Join Date: Feb 2010
Posts: 213
Rep Power: 17 |
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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