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！

Take a look at the interFoam/UEqn.H:

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

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?

I think so.

Fumiya

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

Regards.

Hi,
I've a question about momentum equation of interFoam. why Area (mesh.magSf()) is multiplied to RHS of equation?

This is based on the divergence operator. We interpolate the deviatoric part of grad(U) to the face and have to multiply it with the surface normal vector (area of the face). As it is given in Hrv thesis, the divergence is approximately the sum of fluxes through the faces.

Thanks for your great answer Tobias. I''ll read the harvoj jasak's thesis for further information.

Regards,