[jcappola]

Hi Foamers,

I've been building up a run case from scratch to simulate a centrifugal compressor for a research project. I'm using openfoam-6 and have started building it up from simpleFoam utilizing the now built in MRFProperties. I have been able to get it generally stable however certain BCs are causing issues and I'm in need of a second opinion. I am wishing to prescribe a totalPressure inlet and a mass flow outlet and I'm using the k-epsilon turbulence model (which is said to have issues in rotating applications), however, I'm attempting to match CFX results that were performed with said BCs. I have a periodic hexa mesh with very well refined cells near the walls (y+ < 1) and as such I have elected to use zeroGradients in lieu of wallFunctions. I would like to use a turbulentKineticEnergyInlet BC on my k field however it causes near immediate instability on simpleFoam whereas prescribing a fixedValue inlet works like a charm. Note, all walls are being treated as noSlip even in the MRF zone.


Here are my BCs for review:

U {
    INLET
    {
        type            pressureDirectedInletVelocity;
        inletDirection    uniform (0 0 1);
        value           $internalField;
    }

    OUTLET
    {
        type            flowRateOutletVelocity;
        massFlowRate    0.1585;
        rho        rho;
        extrapolateProfile    yes;
        rhoOutlet    1.225;
        value        uniform (0 0 0);
    }

}


p {
    INLET
    {
        type            totalPressure;
        p0        uniform 101325; // 1 atm
        rho        rho;
        rhoInlet    1.225;

        value        uniform 0;
    }

    OUTLET
    {
        type            zeroGradient;
    }

}


nut {
    INLET
    {
        type            calculated;
        value           uniform 0;
    }

    OUTLET
    {
        type            calculated;
        value           uniform 0;
    }
}


k {
    INLET
    {
        type        turbulentIntensityKineticEnergyInlet;
        intensity    0.05;
        value           uniform 1;
    }

    OUTLET
    {
        type            zeroGradient;
    }

}


epsilon {
    INLET
    {
        type            fixedValue;
        value           uniform 20;
    }

    OUTLET
    {
        type            zeroGradient;
    }
}

Any input is greatly appreciated. Thank you!