[rajan19us]

Hello Foamers,

I am running water-atmosphere interface simulation in a complex domain. As it can be seen in the attached screenshot, the simulation is diverging after around 12000 iterations.
To reach this point, I tweaked relaxation factors and finallz found a combination with which the simulation was converging.

What could be the probable reasons for the simulation to diverge after behaving normallz at the start??

FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location system;
    object fvSolution;
}

    solvers
    {
        "alpha.water_copy.*"
        {
            nAlphaCorr 2;
            nAlphaSubCycles 1;
            cAlpha 1;
            MULESCorr yes;
            nLimiterIter 2;
            solver smoothSolver;
            smoother symGaussSeidel;
            tolerance 1e-5;
            relTol 0.0;
        }

        "pcorr.*"
        {
            solver GAMG;
            preconditioner GAMG;
            tolerance 1e-3;
            relTol 0.0;
            smoother GaussSeidel;
            nPreSweeps 0;
            nPostSweeps 2;
            nFinestSweeps 2;
            cacheAgglomeration true;
            nCellsInCoarsestLevel 100;
            agglomerator faceAreaPair;
            mergeLevels 1;
            minIter 1;
        }

        p_rgh
        {
            solver GAMG;
            agglomerator faceAreaPair;
            mergeLevels 1;
            cacheAgglomeration no;
            nCellsInCoarsestLevel 10;
            tolerance 1e-5;
            relTol 0.02;
            smoother GaussSeidel;
            nPreSweeps 0;
            nPostSweeps 2;
            nFinestSweeps 2;
            minIter 1;
        }

        p_rghFinal
        {
            solver GAMG;
            smoother GaussSeidel;
            agglomerator faceAreaPair;
            mergeLevels 1;
            cacheAgglomeration true;
            nCellsInCoarsestLevel 256;
            tolerance 1e-3;
            relTol 0.0;
            nPreSweeps 0;
            nPostSweeps 2;
            nFinestSweeps 2;
            minIter 1;
        }

        U
        {
            solver smoothSolver;
            smoother GaussSeidel;
            tolerance 1e-3;
            relTol 0.01;
            minIter 1;
        }

        UFinal
        {
            solver smoothSolver;
            smoother GaussSeidel;
            tolerance 1e-3;
            relTol 0.0;
            minIter 1;
        }

    }

    PIMPLE
    {
        momentumPredictor on;
        nOuterCorrectors 50;
        nCorrectors 1;
        nNonOrthogonalCorrectors 1;
        residualControl
        {
            p_rgh
            {
                relTol 0.0;
                tolerance 1.0E-3;
            }

            U
            {
                relTol 0.0;
                tolerance 1.0E-3;
            }

            alpha.water_copy
            {
                tolerance 1.0E-3;
                relTol 0.0;
            }

        }

    }

    relaxationFactors
    {
        equations
        {
            ".*" 1;
            U 0.3;
            UFinal 1.0;
            alpha.water_copy 1.0;
            alpha.water_copyFinal 1.0;
        }

        fields
        {
            p_rgh 0.3;
            p_rghFinal 1;
        }

    }

FoamFile
{
    version 2.0;
    format ascii;
    class dictionary;
    location system;
    object controlDict;
}

    application interFoam;
    startFrom startTime;
    startTime 0;
    stopAt endTime;
    endTime 0.02;
    deltaT 1.0E-7;
    writeControl adjustableRunTime;
    writeInterval 0.005;
    purgeWrite 0;
    writeFormat ascii;
    writePrecision 8;
    writeCompression uncompressed;
    timeFormat general;
    timePrecision 6;
    graphFormat raw;
    runTimeModifiable yes;
    adjustTimeStep true;
    maxCo 2.0;
    maxAlphaCo 1.0;
    maxDeltaT 1.0;

Checking geometry...
    Overall domain bounding box (-0.0208 -0.026000001 -3.1211903e-07) (1.4953394e-08 0.037999999 0.0050045401)
    Mesh has 3 geometric (non-empty/wedge) directions (1 1 1)
    Mesh has 3 solution (non-empty) directions (1 1 1)
    Boundary openness (6.4313919e-15 -2.2156182e-15 -1.5696621e-14) OK.
    Max cell openness = 3.5470582e-16 OK.
    Max aspect ratio = 15.799183 OK.
    Minimum face area = 5.3008842e-12. Maximum face area = 2.5102548e-07.  Face area magnitudes OK.
    Min volume = 3.5968209e-16. Max volume = 1.0664251e-10.  Total volume = 1.7086181e-06.  Cell volumes OK.
    Mesh non-orthogonality Max: 69.964055 average: 10.019463
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 3.2972868 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End
Regards,
Rajan