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-   -   Vortex Street with pisoFoam (http://www.cfd-online.com/Forums/openfoam-solving/89367-vortex-street-pisofoam.html)

mikahs June 10, 2011 09:00

Vortex Street with pisoFoam
 
Hello people...

I am fairly new to CFD and OpenFOAM, so I am not very sure about some results I am getting while simulating a vortex street with a flow around a cylinder.

I was asked to use pisoFoam with laminar flow, and simulate a given mesh (with the cylinder) at Re=20, Re=200 (the vortex street should appear here) and Re=2000.

At Re=20, I had no problems with convergence, with 8000 Iterations my residuals were below 10E-5.

However at Re=200 and at Re=2000 the residuals oscillate asymptotically.

Example: Re=200

http://img707.imageshack.us/img707/7...erre200.th.jpg

Uploaded with ImageShack.us

I would like to know whether this behaviour in my residuals is normal for vortex street calculations, or if I am really having some problems of some other kind.

Ah, and I forgot to say... Courant-Nr<1 ... :/

Code:

ddtSchemes
{
    default        Euler;
}

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

divSchemes
{
    default        none;
    div(phi,U)      Gauss limitedLinearV 1;
    div(phi,k)      Gauss limitedLinear 1;
    div(phi,epsilon) Gauss limitedLinear 1;
    div(phi,R)      Gauss limitedLinear 1;
    div(R)          Gauss linear;
    div(phi,nuTilda) Gauss limitedLinear 1;
    div((nuEff*dev(grad(U).T()))) Gauss linear;
}

laplacianSchemes
{
    default        none;
    laplacian(nuEff,U) Gauss linear corrected;
    laplacian((1|A(U)),p) Gauss linear corrected;
    laplacian(DkEff,k) Gauss linear corrected;
    laplacian(DepsilonEff,epsilon) Gauss linear corrected;
    laplacian(DREff,R) Gauss linear corrected;
    laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;
}

interpolationSchemes
{
    default        linear;
    interpolate(U)  linear;
}

snGradSchemes
{
    default        corrected;
}

fluxRequired
{
    default        no;
    p              ;
}

Code:

solvers
{
    p
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance      1e-06;
        relTol          0.1;
    }

    pFinal
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance      1e-06;
        relTol          1e-4;
    }

    U
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance      1e-05;
        relTol          0;
    }

}

PISO
{
    nCorrectors    3;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue      0;
}



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