CFD Online Discussion Forums - Lag while running DES with pimpleFoam

Hello fellow Foamers!

I was wondering if anyone has experienced a sort of "lag" upon reaching the nuTilda calculation step while doing a DDES simulation with pimpleFoam?

Im running my case in parallel on 128 cpu's with approx 50k cells on each. All other variables seem to be calculated almost instantantly but when it reaches nuTilda it seems to freeze or lag for a second or two and then continue. And it only does one iteration on nuTilda, it shouldn't take so long right? This lag causes my simulation time to pretty much double which is really not good since it already is quite long.

Anyone experienced this or something similar? Any known solutions on how to prevent this?

I suspect there could be something wrong with my fvSolution or fvSchemes setup so I'm posting these below.

Code:

/*--------------------------------*- C++ -*----------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  2.0.1                                 |

|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |

|    \\/     M anipulation  |                                                 |

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

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    location    "system";

    object      fvSchemes;

}

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



ddtSchemes

{

    default         CrankNicholson 0.5;

}



gradSchemes

{

    default         Gauss linear;

    grad(p)         Gauss linear;

    grad(U)         Gauss linear;

}



divSchemes   // filteredLinear(2) is best according to Eugene de Villiers

{

    default         none;

    div(phi,U)      Gauss limitedLinearV 1;

    div(phi,nuTilda) Gauss upwind;

    div((nuEff*dev(T(grad(U))))) Gauss linear;

}



laplacianSchemes

{

    default         none;

    laplacian(nuEff,U) Gauss linear corrected; //limited 0.5;

    laplacian((1|A(U)),p) Gauss linear corrected; // limited 0.5;

    laplacian(DnuTildaEff,nuTilda) Gauss linear corrected; // limited 0.5;

    laplacian(1,p)  Gauss linear corrected; // limited 0.5;

}



interpolationSchemes

{

    default         linear;

    interpolate(U)  linear;

}



snGradSchemes

{

    default         corrected;

}



fluxRequired

{

    default         no;

    p               ;

}





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

Code:

/*--------------------------------*- C++ -*----------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  2.0.1                                 |

|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |

|    \\/     M anipulation  |                                                 |

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

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    location    "system";

    object      fvSolution;

}

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



solvers

{

    p

    {

        solver          GAMG;

        tolerance       1e-04;

        //relTol          0.01;

        smoother        GaussSeidel;

        cacheAgglomeration true;

        nCellsInCoarsestLevel 10;

        agglomerator    faceAreaPair;

        mergeLevels     1;



//         solver          PCG;

//         preconditioner  FDIC;

//         tolerance       1e-04;

//         //relTol          0.1;

//         maxIter                500;

    }



    pFinal

    {

        solver          GAMG;

        tolerance       1e-05;

        //relTol          0.01;

        smoother        GaussSeidel;

        cacheAgglomeration true;

        nCellsInCoarsestLevel 10;

        agglomerator    faceAreaPair;

        mergeLevels     1;



//         solver          PCG;

//         preconditioner  FDIC;

//         tolerance       1e-05;

//         //relTol          0.1;

//         maxIter                500;

    }



    "(U|nuTilda)"

    {

        solver          PBiCG;

        preconditioner  DILU;

        tolerance       1e-06;

        //relTol          0.1;

    }



    "(U|nuTilda)Final"

    {

        solver          PBiCG;

        preconditioner  DILU;

        tolerance       1e-06;

        //relTol          0.1;

    }

}



// PISO

// {

//     nCorrectors     2;

//     nNonOrthogonalCorrectors 0;

//     pRefCell        0;

//     pRefValue       0;

// }



PIMPLE

{

  nOuterCorrectors 2;

    nCorrectors     2;

    nNonOrthogonalCorrectors 0;

    pRefCell        0;

    pRefValue       0;

}



relaxationFactors

{

    "p.*"               0.3;

    "U.*"               0.5;

    "nuTilda.*"         0.5;

}





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

Thanks!