[behzad-cfd]

Hi Dear Foamers,

I've some questions about UEqn.H interFoam.

    if (pimple.momentumPredictor())
    {
        solve
        (
            UEqn
         ==
            fvc::reconstruct
            (
                (
                    fvc::interpolate(interface.sigmaK())*fvc::snGrad(alpha1)
                  - ghf*fvc::snGrad(rho)
                  - fvc::snGrad(p_rgh)
                ) * mesh.magSf()
            )
        );
    }

1- Why right hand side is multiplied by area (mesh.magSf())?
2- Why every thing is in surface form (surface normal gradient, fvc::interpolate) and then reconstructed to cell values? couldn't every thing be in cell centered values from first place?

I'll be appreciated if someone make clear these to me.

Thanks in advance,

Behzad