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interFoam Drag / bubbleFoam instability

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Old   February 14, 2012, 09:08
Default interFoam Drag / bubbleFoam instability
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Rob
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Dear Foamers,

I am working on a multiphase flow simulation inside a steam drum. Therefore, I used the interFoam solver which actually solved the case pretty well. The problem that occured is the drag that is very high I assume. Thus, the steam-water "mixture" is not separated well enough and steam bubbles are pushed under the separation wall.... The attached picture illustrates the problem...

So, in order to optimise the simulation results, there are basically two options.

The first option is to just give bubbleFoam a try. I already did that. But since the 2D test case has a lot of problems in terms of stability I think it will take quite some time to get the simulation stable enough to reach convergence... This leads to the first question: Does anyone have any good fvSchemes / fvSolution entries that proved to be stable?

The second option is to implement a drag model into interFoam. Is this possible? I think that drag needs two velocity vector fields and not just one...

Any help would be appreciated.
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Old   February 20, 2012, 06:08
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Rob
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I am still having problems with the bubbleFoam solver in terms of stability.
Since interFoam uses the MULES algorithm for the liquid phase and bubbleFoam uses a solver that has to be picked by the user, wrong options might be the problem here.
In comparison with interFoam the simulation time is like 1000 times higher.

Since I did not find any real help in old forum posts, I hope someone might have a hint of what options might be stable and fast enough for a quicker simulation.

solvers
{
p
{
solver GAMG;
tolerance 1e-5;//1e-6
relTol 0;
smoother GaussSeidel;
nPreSweeps 0;
nPostSweeps 2;
nFinestSweeps 2;
cacheAgglomeration on;
nCellsInCoarsestLevel 10;
agglomerator faceAreaPair;
mergeLevels 1;

}
alpha
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-10;
relTol 0.0;
}


"(k|epsilon)"
{
solver smoothSolver;
smoother GaussSeidel;
tolerance 1e-5;
relTol 0;
nSweeps 1;

}
}

ddtSchemes
{
default Euler;
}

gradSchemes
{
default faceMDLimited Gauss linear 0;;
}

divSchemes
{
default Gauss upwind;
div(phi,alpha) Gauss vanLeer01;
div((-nuEffa*T(grad(Ua)))) Gauss linear;
div((-nuEffb*T(grad(Ub)))) Gauss linear;
}

laplacianSchemes
{
default Gauss linear limited 0.33;
}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default limited 0.33;
}

fluxRequired
{
default no;
p ;
}
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