Problem with "variableHeightFlowRateInletVelocity" BC and Tetrahedral Mesh-interFoaM

mecbe2002 · July 13, 2023, 07:02

Hi all,

I am trying to simulate open channel flow with variable height inlet (based on intet flow rate the water level will change) boundary condition using interFoam. The simulation runs fine with HEX mesh; but with TET mesh the alpha.water plot is weird at inlet.

I cannot share the actual geometry, so I ran the simulation with simple open channel bend with same simulation setup for both HEX and TET mesh. I have attached the plots and solver setup.

Please let me know what is the issue with the problem setup?

Code:

Boundary Condition - U
inlet - variableHeightFlowRateInletVelocity
outlet - pressureInletOutletVelocity
wall - noSlip
atmosphere - pressureInletOutletVelocity

Boundary Condition - p_rgh
inlet - zeroGradient
outlet - prghTotalPressure
wall - fixedFluxPressure
atmosphere - prghTotalPressure

Boundary Condition - k
inlet - fixedValue
outlet - inletOutlet
wall - kqRWallFunction
atmosphere - inletOutlet

Boundary Condition - epsilon
inlet - fixedValue
outlet - inletOutlet
wall - epsilonWallFunction
atmosphere - inletOutlet

Boundary Condition - alpha.water
inlet - variableHeightFlowRate
outlet - inletOutlet
wall - inletOutlet
atmosphere - zeroGradient

Code:

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         cellLimited Gauss linear 1;
}

divSchemes
{
    div(rhoPhi,U)  Gauss upwind;//linearUpwind grad(U);
    div(phi,alpha)  Gauss PLIC interfaceCompression vanLeer 1; //vanLeer;
    div(phi,k)      Gauss upwind;
    div(phi,epsilon) Gauss upwind;
    div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

wallDist
{
    method meshWave;
}

Code:

solvers
{
    "alpha.water.*"
    {
        nAlphaCorr      1;
        nAlphaSubCycles 1;
        cAlpha          1;
        MULESCorr       yes;
        nLimiterIter    5;

        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-06;
        relTol          0.0;
    }
    
    
    "pcorr.*"
    {
        solver           PCG;
        preconditioner   DIC;
        tolerance        1e-6;
        relTol           0.0;
    }

    p_rgh
    {
        
        solver           PCG;
        preconditioner   DIC;
        tolerance        1e-6;
        relTol           0.0;
    };

    p_rghFinal
    {
        $p_rgh;
        tolerance       1e-6;
        relTol          0;
    }

    "(U|k|epsilon)"
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-06;
        relTol          0.0;
    }
    
    "(U|k|epsilon)Final"
    {
        $U;
        relTol          0;
    }
    
}

PIMPLE
{
    momentumPredictor no;
    nOuterCorrectors  1;
    nCorrectors     2;
    nNonOrthogonalCorrectors 0;
}

relaxationFactors
{
    /**equations
    {
        ".*" 1;
    }**/
    equations
    {
        "U.*"                       0.7;
        "p.*"                       0.7;
        "(k|epsilon).*"             0.7;
        "alpha.water.*"             0.7;
    }
}

Initial Condition : Attachment 95362

Hex Mesh result : Attachment 95363

Tet Mesh result : Attachment 95364