[Fouch]

Hi,


I am trying to calculate a fan that I already know the performance. To do that, I use simpleFoam in Openfoam 2006. The computation seems to converge but the results diverge from the expected performance ???


controlDict

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

saveIter 50;

application     simpleFoam;

startFrom       startTime;
//startFrom     latestTime;
startTime       0;
stopAt          endTime;
endTime         500;
deltaT          1;
writeControl    timeStep;
writeInterval   $saveIter;
purgeWrite      0;
writeFormat     ascii;
writePrecision  7;
writeCompression off;
timeFormat      general;
timePrecision   6;
runTimeModifiable true;

functions
{
    
    forcesBlades
{
    type          forces;

    libs          (forces);

    log           yes;

    patches       (fan);
    rho           rhoInf;     // Indicates incompressible
    log           true;
    rhoInf        0.607;          // Redundant for incompressible

    CofR          (0 0 0);    // Rotation around centre line of propeller
    pitchAxis     (1 0 0);
}


    yPlusPump
    {
        type            yPlus;
        libs ("libfieldFunctionObjects.so");
        writeControl   timeStep;
        writeInterval  $saveIter;
        patches         ("fan wallinlet body");

     }
}
// ************************************************************************* //

fvSolution

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

SIMPLE
{
    // Non-orthogonal correctors for robustness on tet meshes. Porous baffles require a
    // higher number of corrections.
    nNonOrthogonalCorrectors 5;
    consistent no;  // Setting this impairs stability of porous baffles

    residualControl
    {
        p 0.0001;
        U 0.0001;
        "(k|epsilon|omega|f|v2|nuTilda)" 0.0001;
    }
    pRefValue   0;
    pRefCell    0;
}

potentialFlow
{
    nNonOrthogonalCorrectors 8;

    PhiRefValue 0;
    PhiRefCell 0;
}

solvers
{
    "(p|p_rgh|pcorr)"
    {
        solver           GAMG;
        tolerance        1e-8;
        relTol           0.01;
        smoother         symGaussSeidel;
        nPreSweeps       0;
        nPostSweeps      2;
        cacheAgglomeration on;
        agglomerator     faceAreaPair;
        nCellsInCoarsestLevel 10;
        mergeLevels      1;
        maxIter          20;
    }

    "(pFinal|p_rghFinal|pcorrFinal)"
    {
        $p;
        relTol          0;
    }

    U
    {
        solver           smoothSolver;
        smoother         symGaussSeidel;
        tolerance        1e-8;
        relTol           0.1;
        nSweeps          1;
    }

    UFinal
    {
        $U;
        relTol           0;
    }

    "(k|omega|nuTilda)"
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-8;
        relTol           0.1;
        nSweeps          1;
        minIter          1;
    }

    "(k|omega|nuTilda)Final"
    {
        $k;
        relTol          0;
    }

    Phi
    {
        solver           GAMG;
        tolerance        1e-7;
        relTol           0.01;
        smoother         GaussSeidel;
        nPreSweeps       0;
        nPostSweeps      2;
        cacheAgglomeration on;
        agglomerator     faceAreaPair;
        nCellsInCoarsestLevel 10;
        mergeLevels      1;
    }
}

relaxationFactors
{
    // Conservative settings to solve reliably on bad
    // meshes
    equations
    {
        U               0.6;
        k               0.5;
        omega           0.5;
    }
    fields
    {
        p               0.3;
    }
}

cache
{
    grad(U);
}

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

fvScheme

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //



ddtSchemes
{
    default         steadyState;
}

divSchemes
{
    default         none;
    // Use second-order accurate convection
    // Bounded schemes for steady-state solution
    div(phi,U)      bounded Gauss linearUpwindV grad(U);
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
    div(div(phi,U)) Gauss linear;
    div(phi,k)      bounded Gauss upwind;
    div(phi,omega)  bounded Gauss upwind;
}

gradSchemes
{
    // Limit gradient to improve stability when bad cells encountered
    // (0 = no limiting; 1 = do not exceed surrounding cells)
    default         cellLimited Gauss linear 0.95;
    grad(p)         Gauss linear;
    grad(p_rgh)     Gauss linear;
    grad(k)         cellLimited Gauss linear 0.9;
    grad(omega)     cellLimited Gauss linear 0.9;
}

laplacianSchemes
{
    // Limited explicit correction to the surface normal gradient,
    // for stability in highly non-orthogonal cells.
    // (0 = uncorrected, fully implicit; 1 = full correction)
    default                     Gauss linear limited 0.3;
    laplacian(DomegaEff,omega)  Gauss linear limited 0.3
    laplacian(DkEff,k)          Gauss linear limited 0.3;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    // Limited explicit correction to the surface normal gradient,
    // for stability in highly non-orthogonal cells.
    // (0 = uncorrected, fully implicit; 1 = full correction)
    default         limited 0.3;
}

wallDist
{
    method meshWave;
}


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

The pressure increase to much but the absorbed power decrease. That make no sense to me.


Thank you.


Best regards,

[Fouch]

I forgot to precise that the BC are mass flow rate at inlet and fixed static pressure at outlet.
k-SST omega for the turbulence.