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-   -   fvm::laplacian appropriate for d/dx(d/dy) (http://www.cfd-online.com/Forums/openfoam/67318-fvm-laplacian-appropriate-d-dx-d-dy.html)

sven August 11, 2009 21:40

fvm::laplacian appropriate for d/dx(d/dy)
 
Hey,

I am currently working on understanding the source code of the LaunderGibsonRSTM model.

In this model the Reynolds Stress equation reads:

Code:

tmp<fvSymmTensorMatrix> REqn
    (
        fvm::ddt(R_)
      + fvm::div(phi_, R_)
      - fvm::Sp(fvc::div(phi_), R_)
    //- fvm::laplacian(Cs*(k_/epsilon_)*R_, R_)
      - fvm::laplacian(DREff(), R_)
      + fvm::Sp(Clg1_*epsilon_/k_, R_)
      ==
        P
      + (2.0/3.0*(Clg1_ - 1)*I)*epsilon_
      - Clg2_*dev(P)

        // wall reflection terms
      + symm
        (
            I*((yr_.n() & reflect) & yr_.n())
          - 1.5*(yr_.n()*(reflect & yr_.n())
          + (yr_.n() & reflect)*yr_.n())
        )*pow(Cmu_, 0.75)*pow(k_, 1.5)/(kappa_*yr_*epsilon_)
    );

My question now concerns the forth term from the top:

Code:

//- fvm::laplacian(Cs*(k_/epsilon_)*R_, R_)
This term seems to represent a part of the diffusion of the turbulent reynolds stresses. However, in all books on turbulence this equation looks like d/dx(Cs*k/epsilon*R*dR/dy), where d/dx and d/dy are derivatives in different directions.

Is it possible to translate this term into OpenFOAM source Code by using the fvm::laplacian scheme, even though the two derivatives (d/dx,d/dy) have different directions?

chai December 10, 2009 13:24

Hi, Sven
I am facing a similar problem. Did you find a solution to your problem?


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