setRDeltaT.C

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#include "isothermalFluid.H"
#include "fvcFlux.H"
#include "fvcSmooth.H"
#include "fvcSurfaceIntegrate.H"
 
// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
void Foam::solvers::isothermalFluid::setRDeltaT()
{
    const volScalarField& psi = thermo.psi();
 
    volScalarField& rDeltaT = trDeltaT.ref();
 
    const dictionary& pimpleDict = pimple.dict();
 
    const scalar maxCo
    (
        pimpleDict.lookupOrDefault<scalar>("maxCo", 0.8)
    );
 
    const scalar rDeltaTSmoothingCoeff
    (
        pimpleDict.lookupOrDefault<scalar>("rDeltaTSmoothingCoeff", 0.02)
    );
 
    const volScalarField rDeltaT0("rDeltaT0", rDeltaT);
 
    // Set the reciprocal time-step from the local Courant number
    rDeltaT.internalFieldRef() =
        fvc::surfaceSum(mag(phi))()()/((2*maxCo)*mesh.V()*rho());
 
    // Set the reciprocal time-step from the local acoustic Courant number
    if (pimple.transonic())
    {
        surfaceScalarField phid("phid", fvc::interpolate(psi)*fvc::flux(U));
 
        rDeltaT.internalFieldRef() =
            max
            (
                rDeltaT(),
                fvc::surfaceSum(mag(phid))()()/((2*maxCo)*mesh.V()*psi())
            );
    }
 
    // Clip to user-defined maximum and minimum time-steps
    scalar minRDeltaT = gMin(rDeltaT.primitiveField());
    if (pimpleDict.found("maxDeltaT") || minRDeltaT < rootVSmall)
    {
        const scalar clipRDeltaT = 1/pimpleDict.lookup<scalar>("maxDeltaT");
        rDeltaT.max(clipRDeltaT);
        minRDeltaT = max(minRDeltaT, clipRDeltaT);
    }
    if (pimpleDict.found("minDeltaT"))
    {
        const scalar clipRDeltaT = 1/pimpleDict.lookup<scalar>("minDeltaT");
        rDeltaT.min(clipRDeltaT);
        minRDeltaT = min(minRDeltaT, clipRDeltaT);
    }
 
    Info<< "Flow time scale min/max = "
        << gMin(1/rDeltaT.primitiveField()) << ", " << 1/minRDeltaT << endl;
 
    // Update the boundary values of the reciprocal time-step
    rDeltaT.correctBoundaryConditions();
 
    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
    (
        pimpleDict.found("rDeltaTDampingCoeff")
     && runTime.timeIndex() > runTime.startTimeIndex() + 1
    )
    {
        // Damping coefficient (1-0)
        const scalar rDeltaTDampingCoeff
        (
            pimpleDict.lookup<scalar>("rDeltaTDampingCoeff")
        );
 
        rDeltaT =
            rDeltaT0
           *max(rDeltaT/rDeltaT0, scalar(1) - rDeltaTDampingCoeff);
 
        Info<< "Damped flow time scale min/max = "
            << gMin(1/rDeltaT.primitiveField())
            << ", " << gMax(1/rDeltaT.primitiveField()) << endl;
    }
}
 
 
// ************************************************************************* //