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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  NatHaz Modeling Laboratory Department of Civil & Environmental Engineering & Earth Sciences University of Notre Dame, USA Email  My Personal CFD Blog 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  NatHaz Modeling Laboratory Department of Civil & Environmental Engineering & Earth Sciences University of Notre Dame, USA Email  My Personal CFD Blog 

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.


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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