[Devin063]

Greetings,

I am using multiphaseEulerFoam to simulate a micro-bioreactor (31mm*18mm*87mm) with a tiny mixer (d=11.4mm) at 300 rpm. It contains water and gas phases. The sparger pumps air into the mixer at -0.00103745 m/s and the gas leaves the micro-bioreactor from the outlet.

I got bounding epsilonm as shown below, sometimes bounding km. And soon the equation will diverge and obtain huge negative pressure or temperature.

bounding epsilonm, min: -0.00814733 max: 16.3522 average: 0.0880985

I have tried different suggestions based on similar threads before, including fine mesh, different discretization schemes, under-relaxation, constraints of pressure, and playing with the initial guess of epsilon and k. None of them works!

My

ddtSchemes
{
    default Euler;
}

gradSchemes
{

    default 	cellLimited leastSquares 0.5;
    nHat     	Gauss linear;	//Face unit interface normal

}

divSchemes
{
    default                         none;

    div(phi,alpha.air)              Gauss vanLeer;
    div(phi,alpha.water)            Gauss vanLeer;
    div(phir,alpha.water,alpha.air) Gauss vanLeer;
    div(phir,alpha.air,alpha.water) Gauss vanLeer;

    "div\(alphaRhoPhi.*,U.*\)"      Gauss limitedLinear 1;
    "div\(phi.*,U.*\)"              Gauss limitedLinear 1;

    "div\(alphaRhoPhi.*,(h|e).*\)"  Gauss limitedLinear 1;
    "div\(alphaRhoPhi.*,K.*\)"      Gauss limitedLinear 1;
    "div\(alphaRhoPhi.*,\(p\|thermo:rho.*\)\)" Gauss limitedLinear 1;

    "div\(alphaRhoPhi.*,(k|epsilon).*\)"  Gauss limitedLinear 1;
    "div\(phim,(k|epsilon)m\)"      Gauss limitedLinear 1;

    "div\(\(\(\(alpha.**thermo:rho.*\)*nuEff.*\)*dev2\(T\(grad\(U.*\)\)\)\)\)" Gauss linear;

}

laplacianSchemes
{
    default         Gauss linear limited 1;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         limited 1;
}

solvers
{
    "alpha.*"
    {
        nAlphaCorr      2;
        nAlphaSubCycles 2;
        nLimiterIter    10;

        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-8;
        relTol          0;

        minIter		1;
    }

    p_rgh
    {
        solver          GAMG;
        smoother        DIC;
        tolerance       1e-8;
        relTol          0.01;
        minIter		3;
    }

    p_rghFinal
    {
        $p_rgh;
        relTol          0;
        minIter		3;
    }

    "U.*"
    {
        solver          PBiCGStab;
        preconditioner  DILU;
        tolerance       1e-08;
        relTol          0;
        minIter         3;
    }

    "e.*"
    {
        solver          PBiCGStab;
        preconditioner  DILU;
        tolerance       1e-08;
        relTol          0;
        minIter         0;
    }

    "(k|epsilon).*"
    {
        solver          PBiCGStab;
        preconditioner  DILU;
        tolerance       1e-08;
        relTol          0;
        minIter         3;
    }
}

PIMPLE
{
    consistent		yes;

    nOuterCorrectors 3;			//1-3
    nCorrectors      2;			//1-2
    nNonOrthogonalCorrectors 1;

}

relaxationFactors
{
    fields
    {
        ".*" 0.7;
    }
    equations
    {
        ".*" 0.7;
    }
}

Really appreciate suggestions and thank you!