[wyj216]

Hallo, my colleagues,

I just begin to use openFoam and want to test it on a 2D foil. The Reynolds number is 8e+7. The mesh is generated using blockMesh. kOmegaSST is used as the turbulence model. The settings are adjusted according to several tutorials.

Firstly i calculated NACA0012 with sharp edge. simpleFoam and SIMPLEC are used. The obtained Cl and Cd seem to be OK, but the vorticity distribution is quite strange, especially near the block interfaces. The mesh figure is attached. Also the yPlus has a jump at the middle chord position, where there is also a block interface. Does anyone have any idea for it


naca0012_mesh.jpg


Screenshot_20190929_164403.jpg

naca0012_yPlus.png

Besides that, I have also calculated a foil with cutted trailing edge. Then the flow near the trailing edge is more strange. Even the pressure distribution is wrong. I carried pimpleFoam simulations after the simpleFoam, the results are improved but still strange.


Foil2_TePressure.jpg

Foil2_Vorticity.jpg


Below are the control, fvScheme and fvSolution dictionaries.

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

application     simpleFoam;

//startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         3000;

deltaT          3.5;

writeControl    timeStep;

writeInterval   100;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

functions 
{
    vorticity1
    {
        type            vorticity;
        libs            ("libfieldFunctionObjects.so");
        writeControl    writeTime;
    }
    
    yPlus1
    {
        type yPlus;
        libs ("libfieldFunctionObjects.so");
        writeControl   writeTime;
    }
    
    forcesCoeffs1
    {
        type        forceCoeffs;
        libs        ("libforces.so");
        log         yes;
        writeFields no;
        writeControl timeStep;
        writeInterval 1;
        patches     (foil);
        CofR        (0 0 0);
        
        rho rhoInf;
        
        magUInf 80;
        lRef    1;
        Aref    1;
        rhoInf 1;
        porosity no;
        
        dragDir (1 0 0);
        liftDir (0 1 0);
        sideDir (0 0 1);
        rollAxis (1 0 0);
        pitchAxis (0 0 1);
        yawAxis (0 1 0);
        
        binData
        {
            nBin        2;
            direction   (1 0 0);
            cumulative  yes;
        }
    }
}

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

ddtSchemes
{
    default         steadyState;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default         none;
    div(phi,U)      bounded Gauss linearUpwind grad(U);
    
    div(phi,k)      bounded Gauss limitedLinear 1; // linearUpwind grad(k);
    div(phi,epsilon) bounded Gauss limitedLinear 1; // linearUpwind grad(epsilon);
    div(phi,omega)  bounded Gauss limitedLinear 1; // linearUpwind grad(omega);
    
    div(phi,nuTilda) bounded Gauss linearUpwind grad(nuTilda);
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

wallDist
{
    method meshWave;
}

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

solvers
{
    p
    {
        solver          GAMG;
        tolerance       1e-06;
        relTol          0.1;
        smoother        GaussSeidel;
    }

    "(U|k|epsilon|R|nuTilda)"
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        nSweeps         2;
        tolerance       1e-08;
        relTol          0.01;
    }
    
    omega
    {
        solver          PBiCGStab;
        preconditioner  DILU;
        tolerance       1e-10;
        relTol          0.1;
    }
}

SIMPLE
{
    nNonOrthogonalCorrectors 2;
    consistent yes;

    residualControl
    {
        p               1e-8;
        U               1e-8;
        nuTilda         1e-8;
        k               1e-8;
        omega           1e-8;
        epsilon         1e-8;
    }
}

relaxationFactors
{
    fields
    {
        p               1.0;
    }
    equations
    {
        U               0.7;
        nuTilda         0.9;
        k               0.7;
        omega           0.7;
        epsilon         0.8;
    }
}

[wyj216]

Here are the other files, if one want to try the case.



0.zip

constant.zip

blockMeshDict.txt

[wyj216]

For the problem near the trailing edge, someone told me that it may be caused by the high aspect ratio cells near the trailing edge.


But I have carried out the simulation with the same mesh using CFX, also kOmegaSST turbulence model and high order advection scheme (I do not know exactly what it is). The result looks much better. Does anyone have similar experience and any explainations?


PS. The problem near the block interfaces show up also in CFX, but much weaker than in openFoam.



6600_CurlZ_TE.jpg

6600_Pressure_TE.jpg