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-   -   where does this term come from (http://www.cfd-online.com/Forums/openfoam-pre-processing/119207-where-does-term-come.html)

Jonathan June 12, 2013 04:43

where does this term come from
 
Hi everyone,

I am solving a turbine case in OF2.1.1 using SRFSimpleFoam using kOmegaSST. I am having some bounding and convergence issues but am confused about a particular term in the divSchemes subdictionary in fvSchemes:

Does anyone know which equation:
Code:

div((nuEff*dev(T(grad(Urel))))) Gauss upwind; //linear;
comes from and why i cannot using Gauss upwind to discretize it - I get fatal read beyond EOF error if i dont use linear with it.

thanks very much in advance
jonathan

immortality June 12, 2013 06:00

Hi Jonathan
I had a problem like this with tauMC in rhoCentralFoam and Bruno said me that its a tensor field not a scalar or vector field that can use upwind schemes.
if you can get more information or others its nice to share.

Jonathan June 12, 2013 08:51

from kOmegaSST turbulence model
 
hi,

so the term comes from the turbulence model (kOmegaSST):

From kOmegaSST.H
Code:

        //- Return the source term for the momentum equation
        virtual tmp<fvVectorMatrix> divDevReff(volVectorField& U) const;

From kOmegaSST.C
Code:

tmp<fvVectorMatrix> kOmegaSST::divDevReff(volVectorField& U) const
{
    return
    (
      - fvm::laplacian(nuEff(), U)
      - fvc::div(nuEff()*dev(T(fvc::grad(U))))
    );
}

As immortality says, this might be a tensor field, and so the standard divSchemes as per the UG do not apply, but i am still not 100% sure.

wyldckat June 16, 2013 11:36

Greetings to all!

@Jonathan: The post Ehsan was talking about is this one: http://www.cfd-online.com/Forums/ope...tml#post429375 - post #4.
And yes, this is basically the same pattern of mathematics going on in this case.

If you run the following command, you'll see that all tutorials in OpenFOAM use "Gauss linear" for this particular kind of div:
Code:

find $FOAM_TUTORIALS -name fvSchemes | xargs grep "T(grad(U"
Best regards,
Bruno

Jonathan June 17, 2013 07:52

thanks
 
Quote:

Originally Posted by wyldckat (Post 434296)
Greetings to all!

@Jonathan: The post Ehsan was talking about is this one: http://www.cfd-online.com/Forums/ope...tml#post429375 - post #4.
And yes, this is basically the same pattern of mathematics going on in this case.

If you run the following command, you'll see that all tutorials in OpenFOAM use "Gauss linear" for this particular kind of div:
Code:

find $FOAM_TUTORIALS -name fvSchemes | xargs grep "T(grad(U"
Best regards,
Bruno

Hi Bruno,

Thanks very much - your help is much appreciated.

Best regards
Jon


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