realizableKE hanging and then exploding

vaina74 · April 19, 2011, 01:49

Hi foamers,

I have some problems with the k-epsilon realizable turbulent model. I already used it for other cases without troubles, so I'm not able to understand what's wrong or what I can improve.

The simulation starts bad, hanging for several minutes, but then it seems to run:

Code:

Time = 1

smoothSolver:  Solving for Ux, Initial residual = 0.470174, Final residual = 0.00400859, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 1, Final residual = 0.00600497, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 1, Final residual = 0.00335194, No Iterations 4
GAMG:  Solving for p, Initial residual = 1, Final residual = 2.767, No Iterations 1000
time step continuity errors : sum local = 0.00166243, global = 9.18302e-06, cumulative = 9.18302e-06
smoothSolver:  Solving for epsilon, Initial residual = 0.000497916, Final residual = 1.88216e-06, No Iterations 4
smoothSolver:  Solving for k, Initial residual = 1, Final residual = 0.00867952, No Iterations 4
ExecutionTime = 751.02 s  ClockTime = 751 s

Anyway, after some hundreds iterations, the computation explode:

Code:

Time = 398

smoothSolver:  Solving for Ux, Initial residual = 0.288734, Final residual = 0.000692462, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 0.288723, Final residual = 0.00069192, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.288259, Final residual = 0.000668387, No Iterations 4
GAMG:  Solving for p, Initial residual = 2.92554e-10, Final residual = 2.92554e-10, No Iterations 0
time step continuity errors : sum local = 5.31272e+87, global = -2.8754e+74, cumulative = -1.25563e+76
smoothSolver:  Solving for epsilon, Initial residual = 0.0914353, Final residual = 8.60873e-05, No Iterations 4
smoothSolver:  Solving for k, Initial residual = 6.30816e-14, Final residual = 6.30816e-14, No Iterations 0
ExecutionTime = 7035.03 s  ClockTime = 7035 s

GGI pair (stitch_in, stitch_out) : 1.71408e+78 1.71091e+78 Diff = 7.54614e+74 or 0.0440244 %
Cyclic GGI pair (cyclic_1, cyclic_2) : 9.55415e+76 9.5507e+76 Diff = -1.62343e+73 or 0.0169919 %
Cyclic GGI pair (symmetry_1, symmetry_2) : 6.86082e+76 6.86082e+76 Diff = 1.06058e+62 or 1.54585e-13 %

I think I can edit something in fvSolution (or fvSchemes?), but I don't know how. Any suggestion? I report both files.

fvSolution

Code:

solvers
{
    p GAMG
    {
        tolerance             1e-8;
        relTol                0.01;
        smoother              GaussSeidel;
        cacheAgglomeration    true;
        nCellsInCoarsestLevel 20;
        agglomerator          faceAreaPair;
        mergeLevels           1;
    };

    U smoothSolver
    {
        smoother              GaussSeidel;
        nSweeps               2;
        tolerance             1e-7;
        relTol                0.01;
    };

    k smoothSolver
    {
        smoother              GaussSeidel;
        nSweeps               2;
        tolerance             1e-7;
        relTol                0.01;
    };

    epsilon smoothSolver
    {
        smoother              GaussSeidel;
        nSweeps               2;
        tolerance             1e-7;
        relTol                0.01;
    };
}

SIMPLE
{
    nNonOrthogonalCorrectors  0;
    pRefCell                  0;
    pRefValue                 0;
}

relaxationFactors
{
    p                 	      0.3;
    U               	      0.5;
    k                         0.5;
    epsilon                   0.5;
}

fvSchemes

Code:

ddtSchemes
{
    default                       steadyState;
}

gradSchemes
{
    default                       faceMDLimited Gauss linear 0.5;
}

divSchemes
{
    default                       none;
    div(phi,U)                    Gauss GammaV 0.2;
    div(phi,k)                    Gauss upwind;
    div(phi,epsilon)              Gauss upwind;
    div(phi,tau)                  Gauss limitedLinear 1;
    div(phi,omega)                Gauss upwind;
    div(phi,nuTilda)              Gauss limitedLinear 1;
    div((nuEff*dev(grad(U).T()))) Gauss linear;
}

laplacianSchemes
{
    default                       Gauss linear limited 0.5;
    laplacian(DomegaEff,omega)    Gauss linear limited 0.33;
//    laplacian(DepsilonEff,epsilon) Gauss linear corrected;
}

interpolationSchemes
{
    default                       linear;
}

snGradSchemes
{
    default                       limited 0.6;
}

fluxRequired
{
    default                       no;
    p;
}