foam-extend4.1-coherent-io/applications/solvers/compressible/realFluidPisoFoam/pEqn.H

rho = thermo.rho();

volScalarField rUA = 1.0/UEqn.A();
U = rUA*UEqn.H();

if (realFluid)
{
    phi =
        fvc::interpolate(rho)*
        (
            (fvc::interpolate(U) & mesh.Sf())
          + fvc::ddtPhiCorr(rUA, rho, U, phi)
        );

    while (piso.correctNonOrthogonal())
    {
        fvScalarMatrix pEqn
        (
            psi*fvm::ddt(p)
          + drhodh*fvc::ddt(h)
          + fvc::div(phi)
          - fvm::laplacian(rho*rUA, p)
        );

        pEqn.solve();

        if (piso.finalNonOrthogonalIter())
        {
            phi += pEqn.flux();
        }
    }
}
else
{
    if (piso.transonic())
    {
        surfaceScalarField phid
        (
            "phid",
            fvc::interpolate(psi)
           *(
                (fvc::interpolate(U) & mesh.Sf())
               + fvc::ddtPhiCorr(rUA, rho, U, phi)
            )
        );

        while (piso.correctNonOrthogonal())
        {
            fvScalarMatrix pEqn
            (
                fvm::ddt(psi, p)
              + fvm::div(phid, p)
              - fvm::laplacian(rho*rUA, p)
            );

            pEqn.solve();

            if (piso.finalNonOrthogonalIter())
            {
                phi == pEqn.flux();
            }
        }
    }
    else
    {
        phi =
        fvc::interpolate(rho)*
        (
            (fvc::interpolate(U) & mesh.Sf())
          + fvc::ddtPhiCorr(rUA, rho, U, phi)
        );

        while (piso.correctNonOrthogonal())
        {
            fvScalarMatrix pEqn
            (
                fvm::ddt(psi, p)
              + fvc::div(phi)
              - fvm::laplacian(rho*rUA, p)
            );

            pEqn.solve();

            if (piso.finalNonOrthogonalIter())
            {
                phi += pEqn.flux();
            }
        }
    }
}

#include "rhoEqn.H"
#include "compressibleContinuityErrs.H"

U -= rUA*fvc::grad(p);
U.correctBoundaryConditions();

DpDt = fvc::DDt(surfaceScalarField("phiU", phi/fvc::interpolate(rho)), p);