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June 27, 2009, 04:44 
Howto get the production and dissipation of TKE??

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Daniel WEI (老魏)
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Anyone knows how to get the production and dissipation of TKE (turbulence kinetic energy)? Thanks
Is it in this way: Code:
volSymmTensorField D = symm(fvc::grad(U)); //volTensorField Dprim = symm(fvc::grad(U  UMean)); volScalarField prod = ((U  UMean)*(U  UMean)) && D; volScalarField epsilon = sgsModel>epsilon();
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~ Daniel WEI  Boeing Research & Technology  China Beijing, China Last edited by lakeat; June 28, 2009 at 06:14. 

July 6, 2010, 10:55 
Production and dissipation of TKE

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Dear Daniel
I am also interested in this topic. Therefore, I would like to know if you found an answer to your question in the meantime. Cheers, Irina 

July 6, 2010, 11:26 

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Daniel WEI (老魏)
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Sorry, it'e been a long time, but doesn't the codes in my last post work for you?
you can try with a channel case and see if its distribution is correct. Bye
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~ Daniel WEI  Boeing Research & Technology  China Beijing, China 

December 13, 2010, 18:51 

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John Deas
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Hi,
why did you take the symmetrical part of grad(U) ? Why didn't you compute Code:
R && fvc::grad(Umean) Regards, JD 

December 14, 2010, 04:55 

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Alberto Passalacqua
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Notice that the method epsilon() returns the SGS dissipation rate. Check doxygen to see how it is computed, depending on the specific model.
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Alberto Passalacqua GeekoCFD  A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM  An opensource implementation of quadraturebased moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. 

December 14, 2010, 09:18 

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John Deas
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Hi Alberto,
thank you for your answer. When I take a look at src\turbulenceModels\LES\incompressible\oneEqEddy\ oneEqEddy.C, I read: Code:
void oneEqEddy::correct(const tmp<volTensorField>& gradU) { GenEddyVisc::correct(gradU); volScalarField G = 2.0*nuSgs_*magSqr(symm(gradU)); solve ( fvm::ddt(k_) + fvm::div(phi(), k_)  fvm::laplacian(DkEff(), k_) == G  fvm::Sp(ce_*sqrt(k_)/delta(), k_) ); bound(k_, k0()); nuSgs_ = ck_*sqrt(k_)*delta(); nuSgs_.correctBoundaryConditions(); } Code:
ce_*sqrt(k_)/delta() Code:
2.0*nuSgs_*magSqr(symm(gradU)) I also do not understand why the symmetric part of the gradient of U is mentionned in the previous post. Regards, JD 

December 14, 2010, 10:34 

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David Boger
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The doubleinner product of a symmetric and asymmetric secondrank tensor is zero, so in that sense, only the symmetric part of gradU "survives" anyway. So using only the symmetric part is harmless, but perhaps unnecessary.
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December 14, 2010, 12:21 

#8  
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Alberto Passalacqua
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Quote:
volScalarField epsilon = sgsModel>epsilon(); does not return what you want. That epsilon is only the SGS epsilon. Since you do DNS, just apply the definition and you will be fine :) Best,
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Alberto Passalacqua GeekoCFD  A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM  An opensource implementation of quadraturebased moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. 

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