setRDeltaT.H

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    Copyright (C) 2020,2025 OpenCFD Ltd.
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License
    This file is part of OpenFOAM.
 
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{
    volScalarField& rDeltaT = trDeltaT.ref();
 
    const dictionary& pimpleDict = pimple.dict();
 
    // Maximum flow Courant number
    scalar maxCo(pimpleDict.get<scalar>("maxCo"));
 
    // Maximum time scale
    scalar maxDeltaT(pimpleDict.getOrDefault<scalar>("maxDeltaT", GREAT));
 
    // Smoothing parameter (0-1) when smoothing iterations > 0
    scalar rDeltaTSmoothingCoeff
    (
        pimpleDict.getOrDefault<scalar>("rDeltaTSmoothingCoeff", 0.1)
    );
 
    // Damping coefficient (1-0)
    scalar rDeltaTDampingCoeff
    (
        pimpleDict.getOrDefault<scalar>("rDeltaTDampingCoeff", 0.2)
    );
 
    // Maximum change in cell temperature per iteration
    // (relative to previous value)
    scalar alphaTemp(pimpleDict.getOrDefault("alphaTemp", 0.05));
 
 
    // The old reciprocal time scale field, with any damping factor
    tmp<volScalarField> rDeltaT0_damped;
 
    // Calculate damped value before applying any other changes
    if
    (
        rDeltaTDampingCoeff < 1
     && runTime.timeIndex() > runTime.startTimeIndex() + 1
    )
    {
        rDeltaT0_damped = (scalar(1) - rDeltaTDampingCoeff)*(rDeltaT);
    }
 
 
    Info<< "Time scales min/max:" << endl;
 
    // Flow time scale
    {
        rDeltaT.ref() =
        (
            fvc::surfaceSum(mag(phi))()()
           /((2*maxCo)*mesh.V()*rho())
        );
 
        // Limit the largest time scale (=> smallest reciprocal time)
        rDeltaT.clamp_min(1/maxDeltaT);
 
        auto limits = gMinMax(rDeltaT.primitiveField());
        limits.reset(1/(limits.max()+VSMALL), 1/(limits.min()+VSMALL));
 
        Info<< "    Flow        = "
            << limits.min() << ", " << limits.max() << endl;
    }
 
    // Reaction source time scale
    {
        volScalarField::Internal rDeltaTT
        (
            mag
            (
               parcels.hsTrans()/(mesh.V()*runTime.deltaT())
             + Qdot
            )
           /(
               alphaTemp
              *rho()
              *thermo.Cp()()()
              *T()
           )
        );
 
        rDeltaT.primitiveFieldRef().clamp_min(rDeltaTT);
 
        auto limits = gMinMax(rDeltaTT.field());
        limits.reset(1/(limits.max()+VSMALL), 1/(limits.min()+VSMALL));
 
        Info<< "    Temperature = "
            << limits.min() << ", " << limits.max() << endl;
    }
 
    // Update the boundary values of the reciprocal time-step
    rDeltaT.correctBoundaryConditions();
 
    // Spatially smooth the time scale field
    if (rDeltaTSmoothingCoeff < 1.0)
    {
        fvc::smooth(rDeltaT, rDeltaTSmoothingCoeff);
    }
 
    // Limit rate of change of time scale (=> smallest reciprocal time)
    // - reduce as much as required
    // - only increase at a fraction of old time scale
    if (rDeltaT0_damped)
    {
        rDeltaT.clamp_min(rDeltaT0_damped());
    }
 
    // Update the boundary values of the reciprocal time-step
    rDeltaT.correctBoundaryConditions();
 
    auto limits = gMinMax(rDeltaT.primitiveField());
    limits.reset(1/(limits.max()+VSMALL), 1/(limits.min()+VSMALL));
 
    Info<< "    Overall     = "
        << limits.min() << ", " << limits.max() << endl;
}
 
 
// ************************************************************************* //