label nAlphaCorr
(
    readLabel(piso.lookup("nAlphaCorr"))
);

label nAlphaSubCycles
(
    readLabel(piso.lookup("nAlphaSubCycles"))
);

if (nAlphaSubCycles > 1)
{
    surfaceScalarField rhoPhiSum = 0.0*rhoPhi;
    dimensionedScalar totalDeltaT = runTime.deltaT();

    for
    (
        subCycle<volScalarField> alphaSubCycle(alpha1, nAlphaSubCycles);
        !(++alphaSubCycle).end();
    )
    {
#       include "alphaEqns.H"
        rhoPhiSum += (runTime.deltaT()/totalDeltaT)*rhoPhi;
    }

    rhoPhi = rhoPhiSum;
}
else
{
#       include "alphaEqns.H"
}

interface.correct();

{
    volScalarField rhoNew = alpha1*rho1 + alpha2*rho2 + alpha3*rho3;

    //solve(fvm::ddt(rho) + fvc::div(rhoPhi));
    //Info<< "density error = "
    //    << max((mag(rho - rhoNew)/mag(rhoNew))().internalField()) << endl;

    rho == rhoNew;
}