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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;
}

{
default        leastSquares;
}

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;
}

{
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;

writeInterval  0.01;

purgeWrite      0;

writeFormat    ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision  6;

runTimeModifiable 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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