openfoam/applications/solvers/multiphase/twoPhaseEulerFoam/alphaEqn.H

{
    word scheme("div(phi,alpha)");
    word schemer("div(phir,alpha)");

    surfaceScalarField phic("phic", phi);
    surfaceScalarField phir("phir", phia - phib);

    if (g0.value() > 0.0)
    {
        surfaceScalarField alphaf(fvc::interpolate(alpha));
        surfaceScalarField phipp(ppMagf*fvc::snGrad(alpha)*mesh.magSf());
        phir += phipp;
        phic += fvc::interpolate(alpha)*phipp;
    }

    for (int acorr=0; acorr<nAlphaCorr; acorr++)
    {
        fvScalarMatrix alphaEqn
        (
             fvm::ddt(alpha)
           + fvm::div(phic, alpha, scheme)
           + fvm::div(-fvc::flux(-phir, beta, schemer), alpha, schemer)
        );

        if (g0.value() > 0.0)
        {
            ppMagf = rUaAf*fvc::interpolate
            (
                (1.0/(rhoa*(alpha + scalar(0.0001))))
               *g0*min(exp(preAlphaExp*(alpha - alphaMax)), expMax)
            );

            alphaEqn -= fvm::laplacian
            (
                (fvc::interpolate(alpha) + scalar(0.0001))*ppMagf,
                alpha,
                "laplacian(alphaPpMag,alpha)"
            );
        }

        alphaEqn.relax();
        alphaEqn.solve();

        #include "packingLimiter.H"

        beta = scalar(1) - alpha;

        Info<< "Dispersed phase volume fraction = "
            << alpha.weightedAverage(mesh.V()).value()
            << "  Min(alpha) = " << min(alpha).value()
            << "  Max(alpha) = " << max(alpha).value()
            << endl;
    }
}

rho = alpha*rhoa + beta*rhob;