foam-extend4.1-coherent-io/applications/solvers/heatTransfer/chtMultiRegionFoam/include/setMultiRegionDeltaT.H

/*---------------------------------------------------------------------------*\
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Global
    setMultiRegionDeltaT

Description
    Reset the timestep to maintain a constant maximum courant and diffusion
    Numbers. Reduction of time-step is immediate, but increase is damped to avoid
    unstable oscillations.

\*---------------------------------------------------------------------------*/

if (adjustTimeStep)
{
    if (CoNum == -GREAT)
    {
        CoNum = SMALL;
    }

    if (DiNum == -GREAT)
    {
        DiNum = SMALL;
    }

    scalar maxDeltaTFluid = maxCo/(CoNum + SMALL);
    scalar maxDeltaTSolid = maxDi/(DiNum + SMALL);

    scalar deltaTFluid =
        min
        (
            min(maxDeltaTFluid, 1.0 + 0.1*maxDeltaTFluid),
            1.2
        );

    runTime.setDeltaT
    (
        min
        (
            min(deltaTFluid, maxDeltaTSolid)*runTime.deltaT().value(),
            maxDeltaT
        )
    );

    Info<< "deltaT = " <<  runTime.deltaT().value() << endl;
}

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