setRDeltaT.H

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{
    volScalarField& rDeltaT = trDeltaT();
 
    const dictionary& pimpleDict = pimple.dict();
 
    scalar maxCo
    (
        pimpleDict.lookupOrDefault<scalar>("maxCo", 0.9)
    );
 
    scalar maxAlphaCo
    (
        pimpleDict.lookupOrDefault<scalar>("maxAlphaCo", 0.2)
    );
 
    scalar rDeltaTSmoothingCoeff
    (
        pimpleDict.lookupOrDefault<scalar>("rDeltaTSmoothingCoeff", 0.1)
    );
 
    label nAlphaSpreadIter
    (
        pimpleDict.lookupOrDefault<label>("nAlphaSpreadIter", 1)
    );
 
    scalar alphaSpreadDiff
    (
        pimpleDict.lookupOrDefault<scalar>("alphaSpreadDiff", 0.2)
    );
 
    scalar alphaSpreadMax
    (
        pimpleDict.lookupOrDefault<scalar>("alphaSpreadMax", 0.99)
    );
 
    scalar alphaSpreadMin
    (
        pimpleDict.lookupOrDefault<scalar>("alphaSpreadMin", 0.01)
    );
 
    label nAlphaSweepIter
    (
        pimpleDict.lookupOrDefault<label>("nAlphaSweepIter", 5)
    );
 
    scalar rDeltaTDampingCoeff
    (
        pimpleDict.lookupOrDefault<scalar>("rDeltaTDampingCoeff", 1.0)
    );
 
    scalar maxDeltaT
    (
        pimpleDict.lookupOrDefault<scalar>("maxDeltaT", GREAT)
    );
 
    volScalarField rDeltaT0("rDeltaT0", rDeltaT);
 
    // Set the reciprocal time-step from the local Courant number
    rDeltaT.dimensionedInternalField() = max
    (
        1/dimensionedScalar("maxDeltaT", dimTime, maxDeltaT),
        fvc::surfaceSum(mag(rhoPhi))().dimensionedInternalField()
       /((2*maxCo)*mesh.V()*rho.dimensionedInternalField())
    );
 
    if (maxAlphaCo < maxCo)
    {
        // Further limit the reciprocal time-step
        // in the vicinity of the interface
 
        volScalarField alpha1Bar(fvc::average(alpha1));
 
        rDeltaT.dimensionedInternalField() = max
        (
            rDeltaT.dimensionedInternalField(),
            pos(alpha1Bar.dimensionedInternalField() - alphaSpreadMin)
           *pos(alphaSpreadMax - alpha1Bar.dimensionedInternalField())
           *fvc::surfaceSum(mag(phi))().dimensionedInternalField()
           /((2*maxAlphaCo)*mesh.V())
        );
    }
 
    // Update tho boundary values of the reciprocal time-step
    rDeltaT.correctBoundaryConditions();
 
    Info<< "Flow time scale min/max = "
        << gMin(1/rDeltaT.internalField())
        << ", " << gMax(1/rDeltaT.internalField()) << endl;
 
    if (rDeltaTSmoothingCoeff < 1.0)
    {
        fvc::smooth(rDeltaT, rDeltaTSmoothingCoeff);
    }
 
    if (nAlphaSpreadIter > 0)
    {
        fvc::spread
        (
            rDeltaT,
            alpha1,
            nAlphaSpreadIter,
            alphaSpreadDiff,
            alphaSpreadMax,
            alphaSpreadMin
        );
    }
 
    if (nAlphaSweepIter > 0)
    {
        fvc::sweep(rDeltaT, alpha1, nAlphaSweepIter, alphaSpreadDiff);
    }
 
    Info<< "Smoothed flow time scale min/max = "
        << gMin(1/rDeltaT.internalField())
        << ", " << gMax(1/rDeltaT.internalField()) << endl;
 
    // Limit rate of change of time scale
    // - reduce as much as required
    // - only increase at a fraction of old time scale
    if
    (
        rDeltaTDampingCoeff < 1.0
     && runTime.timeIndex() > runTime.startTimeIndex() + 1
    )
    {
        rDeltaT = max
        (
            rDeltaT,
            (scalar(1.0) - rDeltaTDampingCoeff)*rDeltaT0
        );
 
        Info<< "Damped flow time scale min/max = "
            << gMin(1/rDeltaT.internalField())
            << ", " << gMax(1/rDeltaT.internalField()) << endl;
    }
}