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Andrea_85 January 24, 2013 12:27

High diffusion in interFoam
 
Hi all,

i am simulating a meniscus that moves in capillary tubes of different shape with small contact angle (from 1 up to 30). I have observed a very large diffusion of the interface which sometimes leads to non-physical or not-expected results. I was wondering if i can limit diffusion without without touching cAlpha, which is set to 1 at the moment, maybe playing with schemes for convective terms. Which schemes can be used in interFoam to limit diffusion?

This is how my fvScheme looks like:
Code:

ddtSchemes
{
    default        Euler;
}

gradSchemes
{
    default        leastSquares;
//    grad(U)        Gauss linear;
//    grad(alpha1)    Gauss linear;
}

divSchemes
{
    div(rho*phi,U)  Gauss limitedLinearV 1;
    div(phi,alpha)  Gauss vanLeer;
    div(phirb,alpha) Gauss interfaceCompression;
}

laplacianSchemes
{
    default        Gauss linear corrected;
}

interpolationSchemes
{
    default        linear;
}

snGradSchemes
{
    default        corrected;
}

fluxRequired
{
    default        no;
    p_rgh;
    pcorr;
    alpha1;
}

and fvSolution

Code:

solvers
{
    pcorr
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance      1e-10;
        relTol          0;
    }

    p_rgh
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance      1e-07;
        relTol          0.05;
    }

    p_rghFinal
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance      1e-07;
        relTol          0;
    }

    U
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance      1e-06;
        relTol          0;
    }
    UFinal
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance      1e-06;
        relTol          0;
    }


PIMPLE
{
    momentumPredictor yes;
    nCorrectors    3;
    nNonOrthogonalCorrectors 1;
    nAlphaCorr      1;
    nAlphaSubCycles 3;
    cAlpha          1;
}

and controlDict

Code:

application    interFoam;

startFrom      startTime;

startTime      0;

stopAt          endTime;

endTime        0.22;

deltaT          0.000000001;

writeControl    adjustableRunTime;

writeInterval  0.01;

purgeWrite      0;

writeFormat    ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision  6;

runTimeModifiable yes;

adjustTimeStep  yes;

maxCo          0.1;
maxAlphaCo      0.1;

maxDeltaT      0.01;

thanks

andrea

akidess January 24, 2013 16:59

Instead of vanLeer you can use MULES or SuperBee, both of which should be more compressive. Don't expect too much though.

Andrea_85 January 31, 2013 05:08

Thanks Anton, i'll give them a try.

best

andrea


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