
[Sponsors] 
Howto get the production and dissipation of TKE?? 
Sponsored Links 

LinkBack  Thread Tools  Display Modes 
June 27, 2009, 04:44 
Howto get the production and dissipation of TKE??

#1 
Senior Member
Daniel WEI (老魏)
Join Date: Mar 2009
Location: Beijing, China
Posts: 689
Blog Entries: 9
Rep Power: 14 
Sponsored Links
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();
__________________
~ Daniel WEI  Boeing Research & Technology  China Beijing, China Last edited by lakeat; June 28, 2009 at 06:14. 

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

#2 
New Member
Join Date: Mar 2010
Posts: 6
Rep Power: 9 
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 

#3 
Senior Member
Daniel WEI (老魏)
Join Date: Mar 2009
Location: Beijing, China
Posts: 689
Blog Entries: 9
Rep Power: 14 
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
__________________
~ Daniel WEI  Boeing Research & Technology  China Beijing, China 

December 13, 2010, 18:51 

#4 
Senior Member
John Deas
Join Date: Mar 2009
Posts: 160
Rep Power: 10 
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 

#5 
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,910
Rep Power: 28 
Notice that the method epsilon() returns the SGS dissipation rate. Check doxygen to see how it is computed, depending on the specific model.
__________________
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 

#6 
Senior Member
John Deas
Join Date: Mar 2009
Posts: 160
Rep Power: 10 
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 

#7 
Senior Member
David Boger
Join Date: Mar 2009
Location: Penn State Applied Research Laboratory
Posts: 146
Rep Power: 10 
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.
__________________
David A. Boger 

December 14, 2010, 12:21 

#8  
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,910
Rep Power: 28 
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,
__________________
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. 

July 9, 2016, 04:56 

#9 
Senior Member
Ehsan Asgari
Join Date: Apr 2010
Posts: 311
Rep Power: 10 
Hi,
This is an old thread, but I wonder if anyone has achieved a reliable method to calculate TKE dissipation?! Regards 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Turbulent Dissipation Rates  epsilon  Otute  Main CFD Forum  5  May 20, 1999 10:51 
Sponsored Links 