CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM (http://www.cfd-online.com/Forums/openfoam/)
-   -   Tubrulence model diffusion term ??? (http://www.cfd-online.com/Forums/openfoam/102872-tubrulence-model-diffusion-term.html)

Tobi June 5, 2012 05:37

Tubrulence model diffusion term ???
 
1 Attachment(s)
hi all together,

i have a question to the RNG-kEpsilon equation respectively to the diffusion term.

Well in the code there is the following equation:

Code:

// Dissipation equation
    tmp<fvScalarMatrix> epsEqn
    (
        fvm::ddt(rho_, epsilon_)
      + fvm::div(phi_, epsilon_)
      - fvm::laplacian(DepsilonEff(), epsilon_)
      ==
        (C1_ - R)*G*epsilon_/k_
      - fvm::SuSp(((2.0/3.0)*C1_ + C3_)*rho_*divU, epsilon_)
      - fvm::Sp(C2_*rho_*epsilon_/k_, epsilon_)
    );

especially to that code!!!
Code:

- fvm::laplacian(DepsilonEff(), epsilon_)
the diffusivity is calculated in the header file like:
Code:

mut_/sigmaEps_ + mu()
Thats all clear but I have that equation in my literature (pdf)
and (please correct me) if I set the diffusion term to the left and transform it I get:

Code:

mu() - mut_/sigmaEps
Hope I asked clearly.
Thx in advance,
tobi

eysteinn June 5, 2012 06:22

Quote:

Originally Posted by Tobi (Post 364790)
hi all together,

i have a question to the RNG-kEpsilon equation respectively to the diffusion term.

Well in the code there is the following equation:

Code:

// Dissipation equation
    tmp<fvScalarMatrix> epsEqn
    (
        fvm::ddt(rho_, epsilon_)
      + fvm::div(phi_, epsilon_)
      - fvm::laplacian(DepsilonEff(), epsilon_)
      ==
        (C1_ - R)*G*epsilon_/k_
      - fvm::SuSp(((2.0/3.0)*C1_ + C3_)*rho_*divU, epsilon_)
      - fvm::Sp(C2_*rho_*epsilon_/k_, epsilon_)
    );

especially to that code!!!
Code:

- fvm::laplacian(DepsilonEff(), epsilon_)
the diffusivity is calculated in the header file like:
Code:

mut_/sigmaEps_ + mu()
Thats all clear but I have that equation in my literature (pdf)
and (please correct me) if I set the diffusion term to the left and transform it I get:

Code:

mu() - mut_/sigmaEps
Hope I asked clearly.
Thx in advance,
tobi


Hmm . . . my literature says nu+nu_t/sigma_epsilon not nu - nu_t/sigma_epsilon for the diffusion term in the epsilon eq..

Tobi June 5, 2012 07:21

Quote:

Originally Posted by eysteinn (Post 364797)
Hmm . . . my literature says nu+nu_t/sigma_epsilon not nu - nu_t/sigma_epsilon for the diffusion term in the epsilon eq..

Well thx for your replay!
I see that in the diffusion term for k its like " nu + nu_t/sigma_k"

I ll have a look at my bible "Ferziger" :)
"May be its just a mistake while copying things :D"


All times are GMT -4. The time now is 21:31.