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-   -   Hi,I have a question about momentum equation in interFoam (http://www.cfd-online.com/Forums/openfoam-programming-development/111631-hi-i-have-question-about-momentum-equation-interfoam.html)

shchao January 11, 2013 10:19

Hi,I have a question about momentum equation in interFoam
 
Dear Foamers:
I have read Henrik Rusche's phd thesis.Now i meet a question in the momentum equation of interFoam. Mr. Rusche defined an 'H' operator AH=As-An*phi where 'As' means source vector.Does As include the item like -grad(p)-g*x*grad(rho)...?Or What included in As?Thank you very much!

fumiya January 13, 2013 06:59

Take a look at the interFoam/UEqn.H:

Code:

    fvVectorMatrix UEqn
    (
        fvm::ddt(rho, U)
      + fvm::div(rhoPhi, U)
      + turbulence->divDevRhoReff(rho, U)
    ==
        sources(rho, U)
    );

In the case of UEqn.H(), 'H' operator is constructed from the above
fvVectorMatrix UEqn. In the above definition of UEqn, there is no
terms corresponding to grad(p) and g*x*grad(rho), so these terms
are not included in the H operator in the interFoam solver.

Fumiya

shchao January 14, 2013 08:47

Here's the UEqn.H in of 2.1.1

surfaceScalarField muEff
(
"muEff",
twoPhaseProperties.muf()
+ fvc::interpolate(rho*turbulence->nut())
);
fvVectorMatrix UEqn
(
fvm::ddt(rho, U)
+ fvm::div(rhoPhi, U)
- fvm::laplacian(muEff, U)
- (fvc::grad(U) & fvc::grad(muEff))
//- fvc::div(muEff*(fvc::interpolate(dev(fvc::grad(U)) ) & mesh.Sf()))
);
UEqn.relax();
if (pimple.momentumPredictor())
{
solve
(
UEqn
==
fvc::reconstruct
(
(
fvc::interpolate(interface.sigmaK())*fvc::snGrad(a lpha1)
- ghf*fvc::snGrad(rho)
- fvc::snGrad(p_rgh)
) * mesh.magSf()
)
);
}

The H operator is constructed by :
fvVectorMatrix UEqn
(
fvm::ddt(rho, U)
+ fvm::div(rhoPhi, U)
- fvm::laplacian(muEff, U)
- (fvc::grad(U) & fvc::grad(muEff))
//- fvc::div(muEff*(fvc::interpolate(dev(fvc::grad(U)) ) & mesh.Sf()))
);

Right?

fumiya January 15, 2013 08:26

I think so.

Fumiya

santiagomarquezd January 28, 2013 22:27

Hi, the H operator gives which is defined in Hrv thesis for the implicit terms used in the fvVectorMatrix declaration.

Regards.


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