setRDeltaT.H

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{
    volScalarField& rDeltaT = trDeltaT.ref();

    const dictionary& pimpleDict = pimple.dict();

    Info<< "Time scales min/max:" << endl;

    // Cache old reciprocal time scale field
    const volScalarField rDeltaT0("rDeltaT0", rDeltaT);

    // Flow time scale
    {
        // Maximum flow Courant number
        const scalar maxCo(pimpleDict.lookup<scalar>("maxCo"));

        rDeltaT.ref() =
        (
            fvc::surfaceSum(mag(phi))()()
           /((2*maxCo)*mesh.V()*rho())
        );

        // Limit the largest time step
        if (pimpleDict.found("maxDeltaT"))
        {
            rDeltaT.max(1/pimpleDict.lookup<scalar>("maxDeltaT"));
        }

        // Limit the smallest time step
        if (pimpleDict.found("minDeltaT"))
        {
            rDeltaT.min(1/pimpleDict.lookup<scalar>("minDeltaT"));
        }

        Info<< "    Flow        = "
            << 1/gMax(rDeltaT.primitiveField()) << ", "
            << 1/gMin(rDeltaT.primitiveField()) << endl;
    }

    // Maximum change in cell temperature per iteration
    // (relative to previous value)
    const scalar alphaTemp(pimpleDict.lookupOrDefault("alphaTemp", 0.05));

    // Heat release rate time scale
    if (alphaTemp < 1)
    {
        volScalarField::Internal rDeltaTT
        (
            mag(reaction->Qdot())/(alphaTemp*rho*thermo.Cp()*T)
        );

        Info<< "    Temperature = "
            << 1/(gMax(rDeltaTT.field()) + vSmall) << ", "
            << 1/(gMin(rDeltaTT.field()) + vSmall) << endl;

        rDeltaT.ref() = max(rDeltaT(), rDeltaTT);
    }

    // Reaction rate time scale
    if (pimpleDict.found("alphaY"))
    {
        // Maximum change in cell concentration per iteration
        // (relative to reference value)
        const scalar alphaY(pimpleDict.lookup<scalar>("alphaY"));

        const dictionary Yref(pimpleDict.subDict("Yref"));

        volScalarField::Internal rDeltaTY
        (
            IOobject
            (
                "rDeltaTY",
                runTime.timeName(),
                mesh
            ),
            mesh,
            dimensionedScalar(rDeltaT.dimensions(), 0)
        );

        bool foundY = false;

        forAll(Y, i)
        {
            if (composition.solve(i))
            {
                volScalarField& Yi = Y[i];

                if (Yref.found(Yi.name()))
                {
                    foundY = true;
                    scalar Yrefi = Yref.lookup<scalar>(Yi.name());

                    rDeltaTY.field() = max
                    (
                        mag
                        (
                            reaction->R(Yi)().source()
                           /((Yrefi*alphaY)*(rho*mesh.V()))
                        ),
                        rDeltaTY
                    );
                }
            }
        }

        if (foundY)
        {
            Info<< "    Composition = "
                << 1/(gMax(rDeltaTY.field()) + vSmall) << ", "
                << 1/(gMin(rDeltaTY.field()) + vSmall) << endl;

            rDeltaT.ref() = max(rDeltaT(), rDeltaTY);
        }
        else
        {
            IOWarningIn(args.executable().c_str(), Yref)
                << "Cannot find any active species in Yref " << Yref
                << endl;
        }
    }

    // Update the boundary values of the reciprocal time-step
    rDeltaT.correctBoundaryConditions();

    // Smoothing parameter (0-1) when smoothing iterations > 0
    const scalar rDeltaTSmoothingCoeff
    (
        pimpleDict.lookupOrDefault<scalar>("rDeltaTSmoothingCoeff", 0.1)
    );

    // Spatially smooth the time scale field
    if (rDeltaTSmoothingCoeff < 1)
    {
        fvc::smooth(rDeltaT, rDeltaTSmoothingCoeff);
    }

    // Limit rate of change of time scale
    // - reduce as much as required
    // - only increase at a fraction of old time scale
    if
    (
        pimpleDict.found("rDeltaTDampingCoeff")
     && runTime.timeIndex() > runTime.startTimeIndex() + 1
    )
    {
        // Damping coefficient (1-0)
        const scalar rDeltaTDampingCoeff
        (
            pimpleDict.lookup<scalar>("rDeltaTDampingCoeff")
        );

        rDeltaT = max
        (
            rDeltaT,
            (scalar(1) - rDeltaTDampingCoeff)*rDeltaT0
        );
    }

    // Update the boundary values of the reciprocal time-step
    rDeltaT.correctBoundaryConditions();

    Info<< "    Overall     = "
        << 1/gMax(rDeltaT.primitiveField())
        << ", " << 1/gMin(rDeltaT.primitiveField()) << endl;
}


// ************************************************************************* //