[oumnion]

Hi,

I am a new user of OF, I am simulating a rotating hydroturbine using pimpleDyMFoam but I have some issues where the simulation crashes after high Co number value and few iterations.

I run the checkMesh, it is okay. If anyone can help me figure out where the problem is, please thank you.

For example:

Courant Number mean: 0.0665607 max: 294.314
Time = 0.0035                              

smoothSolver:  Solving for Uz, Initial residual = 0.000988812, Final residual = 8.59295e-07, No Iterations 6
AMI: Creating addressing and weights between 18784 source faces and 18784 target faces                      
smoothSolver:  Solving for Ux, Initial residual = 0.00213788, Final residual = 1.06473e-06, No Iterations 5 
AMI: Patch source sum(weights) min/max/average = 0.999999, 1.00004, 1.00001                                 
AMI: Patch target sum(weights) min/max/average = 0.997471, 1.00004, 0.999978                                
smoothSolver:  Solving for Uy, Initial residual = 0.00214001, Final residual = 2.03012e-06, No Iterations 4 
smoothSolver:  Solving for Uz, Initial residual = 0.00257939, Final residual = 1.7967e-06, No Iterations 5  
PIMPLE: iteration 1                                                                                         
smoothSolver:  Solving for Ux, Initial residual = 0.000304317, Final residual = 5.73925e-07, No Iterations 7
smoothSolver:  Solving for Uy, Initial residual = 0.000301525, Final residual = 8.5824e-07, No Iterations 6 
smoothSolver:  Solving for Uz, Initial residual = 0.000429538, Final residual = 8.4974e-07, No Iterations 7 
PIMPLE: iteration 1                                                                                         
smoothSolver:  Solving for Ux, Initial residual = 0.0214581, Final residual = 1.67677e-05, No Iterations 3  
smoothSolver:  Solving for Uy, Initial residual = 0.0214571, Final residual = 1.4444e-05, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.0245988, Final residual = 2.12498e-05, No Iterations 3
GAMG:  Solving for p, Initial residual = 0.0103925, Final residual = 9.27148e-06, No Iterations 8
time step continuity errors : sum local = 2.14296e-08, global = -2.31864e-09, cumulative = 3.61365e-07
smoothSolver:  Solving for Ux, Initial residual = 0.0214581, Final residual = 1.67677e-05, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.0214571, Final residual = 1.4444e-05, No Iterations 3
PIMPLE: iteration 5
smoothSolver:  Solving for Uz, Initial residual = 0.0245988, Final residual = 2.12498e-05, No Iterations 3
GAMG:  Solving for p, Initial residual = 0.02332, Final residual = 2.00854e-05, No Iterations 7
time step continuity errors : sum local = 4.63087e-08, global = -5.40695e-09, cumulative = 3.63684e-07
PIMPLE: iteration 4
GAMG:  Solving for p, Initial residual = 0.00487913, Final residual = 3.59641e-06, No Iterations 7
time step continuity errors : sum local = 8.28061e-09, global = -3.505e-09, cumulative = 3.5786e-07
smoothSolver:  Solving for Ux, Initial residual = 0.000304317, Final residual = 5.73925e-07, No Iterations 7
GAMG:  Solving for p, Initial residual = 0.023441, Final residual = 1.95274e-05, No Iterations 6
time step continuity errors : sum local = 4.43837e-08, global = -1.11018e-08, cumulative = 3.46758e-07
smoothSolver:  Solving for Uy, Initial residual = 0.000301525, Final residual = 8.5824e-07, No Iterations 6
PIMPLE: iteration 2
smoothSolver:  Solving for Uz, Initial residual = 0.000429538, Final residual = 8.4974e-07, No Iterations 7
smoothSolver:  Solving for omega, Initial residual = 0.000412129, Final residual = 6.34727e-07, No Iterations 4
smoothSolver:  Solving for Ux, Initial residual = 0.000718585, Final residual = 6.28164e-07, No Iterations 6
GAMG:  Solving for p, Initial residual = 0.023441, Final residual = 1.95274e-05, No Iterations 6
time step continuity errors : sum local = 4.43837e-08, global = -1.11018e-08, cumulative = 3.46758e-07
smoothSolver:  Solving for Uy, Initial residual = 0.000718183, Final residual = 5.84072e-07, No Iterations 6
PIMPLE: iteration 2
smoothSolver:  Solving for k, Initial residual = 0.0207893, Final residual = 6.86243e-06, No Iterations 3
PIMPLE: not converged within 5 iterations
smoothSolver:  Solving for Uz, Initial residual = 0.000988812, Final residual = 8.59295e-07, No Iterations 6
smoothSolver:  Solving for Ux, Initial residual = 0.00706966, Final residual = 4.63885e-06, No Iterations 6
ExecutionTime = 976.44 s  ClockTime = 1035 s

[Sugajen]

Hi oumnia,

Welcome to OF!

Regarding your question, there could be various reasons for a high Courant number. My quick question now will be did you try setting adjustTimeStep to yes and the max Courant number to a lower value?
If your answer is yes, then please do post your boundary conditions, fvSchemes, fvSolutions and other necessary data so that people who can help can get a better hold on the issue.

best,
Sugajen

[sheaker]

Could You show us Your 'checkMesh' report, please? Usually new users misunderstand the report.

[oumnion]

Yes, I did set adjustTimeStep to yes
I attached my boundary conditions
Here is my fvSchemes:

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
    grad(p)         cellLimited Gauss linear 1;
    grad(U)         cellLimited Gauss linear 1;
}

divSchemes
{
    default         none;
    div(phi,U)      Gauss linearUpwind grad(U);
    div(phi,k)      Gauss upwind;
    div(phi,omega)  Gauss upwind;
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear limited corrected 0.5;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    pcorr           ;
    p               ;
}

wallDist
{
    method meshWave;
}

fvSolution

solvers
{
    pcorr
    {
        solver          GAMG;
        tolerance       1e-4;
        relTol          0.001;
    nPreSweeps    0;
    nPostSweeps    2;
        smoother        DICGaussSeidel;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator    faceAreaPair;
        mergeLevels     1;
        maxIter         10;
    }

    p
    {
        $pcorr;
        tolerance       1e-5;
        relTol          0.001;
        maxIter         10;
    }

    pFinal
    {
        $p;
        tolerance       1e-6;
        relTol          0.001;
        maxIter         10;
    }

    "(U|k|omega)"
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        tolerance       1e-6;
        relTol          0.001;
        maxIter         20;
    }

    "(U|k|omega)Final"
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        tolerance       1e-6;
        relTol          0.001;
        maxIter         20;
    }
}

PIMPLE
{
    correctPhi          no;
    nOuterCorrectors    5;
    nCorrectors         1;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue        0;

    residualControl
    {
        U
        {
        tolerance 1e-2;
        relTol    0.001;
    }

    p
    {
        tolerance 1e-2;
        relTol    0.001;
    }
    }
}

relaxationFactors
{
    fields
    {
    p        0.7;
    }
    equations
    {
    "(U|k|omega)"    0.7;
    "(U|k|omega)Final" 0.7; 
    }
}

cache
{
    grad(U);
}