setRDeltaT.H

{
    volScalarField& rDeltaT = trDeltaT.ref();
 
    const dictionary& pimpleDict = pimple.dict();
 
    scalar maxCo
    (
        pimpleDict.getOrDefault<scalar>("maxCo", 0.8)
    );
 
    scalar rDeltaTSmoothingCoeff
    (
        pimpleDict.getOrDefault<scalar>("rDeltaTSmoothingCoeff", 0.02)
    );
 
    scalar rDeltaTDampingCoeff
    (
        pimpleDict.getOrDefault<scalar>("rDeltaTDampingCoeff", 1.0)
    );
 
    scalar maxDeltaT
    (
        pimpleDict.getOrDefault<scalar>("maxDeltaT", GREAT)
    );
 
    volScalarField rDeltaT0("rDeltaT0", rDeltaT);
 
    // Set the reciprocal time-step from the local Courant number
    rDeltaT.ref() = max
           (
               1 / dimensionedScalar("maxDeltaT", dimTime, maxDeltaT),
               fvc::surfaceSum(mag(phi))()()
               / ((2 * maxCo) * mesh.V() * rho())
           );
 
    if (pimple.transonic())
    {
        surfaceScalarField phid
        (
            "phid",
            fvc::interpolate(psi)*fvc::flux(U)
        );
        rDeltaT.ref() = max
               (
                   rDeltaT(),
                   fvc::surfaceSum(mag(phid))()()
                   / ((2 * maxCo) * mesh.V() * psi())
               );
    }
 
    // Update tho boundary values of the reciprocal time-step
    rDeltaT.correctBoundaryConditions();
 
    Info << "Flow time scale min/max = "
         << gMin(1 / rDeltaT.primitiveField())
         << ", " << gMax(1 / rDeltaT.primitiveField()) << endl;
 
    if (rDeltaTSmoothingCoeff < 1.0)
    {
        fvc::smooth(rDeltaT, rDeltaTSmoothingCoeff);
    }
 
    Info << "Smoothed flow time scale min/max = "
         << gMin(1 / rDeltaT.primitiveField())
         << ", " << gMax(1 / rDeltaT.primitiveField()) << 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 =
        rDeltaT0
        * max(rDeltaT / rDeltaT0, scalar(1) - rDeltaTDampingCoeff);
        Info << "Damped flow time scale min/max = "
             << gMin(1 / rDeltaT.primitiveField())
             << ", " << gMax(1 / rDeltaT.primitiveField()) << endl;
    }
}