EHD model very low deltaT

mcfdma · November 3, 2020, 05:56

Hello,

I am working on an electrohydrodynamics (EHD) model and have issues with deltaT.
http://openfoamwiki.net/index.php/Co...ectromagnetics
EHDFoam

With the same setup, for lower electrical conductivity $\sigma$ , my solver works fine with deltaT in order of 1e-8. However, when I use a different fluid which has higher electrical conductivity (and because of that need to choose a lower flow rate = low Ux), the detlaT is in the order of 1e-77.

Could anyone guide how I can bring deltaT back to normal???

I am including a small section of log file using GAMG solver if useful:

Code:

PIMPLE: iteration 1
MULES: Solving for alpha.water
MULES: Solving for alpha.water
Phase-1 volume fraction = 0.0005588225373  Min(alpha.water) = -1.524317027e-22  Max(alpha.water) = 1.000000002
DICPCG:  Solving for Ue, Initial residual = 1.943188846e-08, Final residual = 9.980163579e-15, No Iterations 588
DILUPBiCG:  Solving for rhoE, Initial residual = 1.376162146e-08, Final residual = 1.4447631e-16, No Iterations 2
GAMG:  Solving for p_rgh, Initial residual = 0.002436202718, Final residual = 0.0001215341975, No Iterations 500
time step continuity errors : sum local = 1.383292408e-10, global = -6.663405978e-12, cumulative = -1.59258934e-07
GAMG:  Solving for p_rgh, Initial residual = 0.0009382469796, Final residual = 4.607140964e-05, No Iterations 534
time step continuity errors : sum local = 6.036468106e-11, global = 2.420807244e-12, cumulative = -1.592565132e-07
GAMGPCG:  Solving for p_rgh, Initial residual = 0.0001156991252, Final residual = 2.222468915e-05, No Iterations 20
time step continuity errors : sum local = 2.734996283e-11, global = -1.46125281e-13, cumulative = -1.592566593e-07
ExecutionTime = 34059.05 s  ClockTime = 34214 s

Courant Number mean: 3.397615704e-05 max: 0.3118083742
Interface Courant Number mean: 2.751246388e-07 max: 0.03718473623
deltaT = 4.329599813e-77
Time = 1.2329e-05

My controlDict:

Code:

application     interFoam;

startFrom       latestTime;

stopAt          endTime;

endTime         0.2;

deltaT          1e-05;

writeControl    adjustableRunTime;

writeInterval   0.02;

purgeWrite      0;

writeFormat     ascii;

writePrecision  10;

writeCompression uncompressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

adjustTimeStep  yes;

maxCo           0.3;
maxAlphaCo      0.2;

maxDeltaT       1;

My fvSchemes:

Code:

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
//    grad
}

divSchemes
{
    default          Gauss linear;
    div(rho*phi,U)   Gauss upwind;
    div(phi,rhoE)    Gauss upwind;
    div(phi,alpha)   Gauss vanLeer;
    div(phirb,alpha) Gauss interfaceCompression;
    div((muEff*dev(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
//    laplacian(eps,Ue) Gauss SuperBee corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    p_rgh;
    pcorr;
    alpha.water;
    rhoE;
}

My fvSolution:

Code:

solvers
{
    "alpha.water.*"
    {
        nAlphaCorr      2;
        nAlphaSubCycles 1;
        cAlpha          1;

       // MULESCorr       yes;
       // nLimiterIter    3;

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

    pcorr
    {
        solver          PCG;
        preconditioner
        {
            preconditioner  GAMG;
            tolerance       0.001;
            relTol          0;
            smoother        GaussSeidel;
            nPreSweeps      0;
            nPostSweeps     2;
            nFinestSweeps   2;
            cacheAgglomeration false;
            nCellsInCoarsestLevel 10;
            agglomerator    faceAreaPair;
            mergeLevels     1;
        }

        tolerance       0.0001;
        relTol          0;
        maxIter         100;
    }
    
        pcorrFinal
    {
        solver          PCG;
        preconditioner
        {
            preconditioner  GAMG;
            tolerance       0.001;
            relTol          0;
            smoother        GaussSeidel;
            nPreSweeps      0;
            nPostSweeps     2;
            nFinestSweeps   2;
            cacheAgglomeration false;
            nCellsInCoarsestLevel 10;
            agglomerator    faceAreaPair;
            mergeLevels     1;
        }

        tolerance       0.0001;
        relTol          0;
        maxIter         100;
    }

    p_rgh
    {
        solver          GAMG;
        tolerance       1e-08;
        relTol          0.05;
        smoother        GaussSeidel;
        nPreSweeps      0;
        nPostSweeps     2;
        nFinestSweeps   2;
        cacheAgglomeration false;
        nCellsInCoarsestLevel 10;
        agglomerator    faceAreaPair;
        mergeLevels     1;
    }

    p_rghFinal
    {
        solver          PCG;
        preconditioner
        {
            preconditioner  GAMG;
            tolerance       1e-08;
            relTol          0;
            nVcycles        2;
            smoother        GaussSeidel;
            nPreSweeps      0;
            nPostSweeps     2;
            nFinestSweeps   2;
            cacheAgglomeration false;
            nCellsInCoarsestLevel 10;
            agglomerator    faceAreaPair;
            mergeLevels     1;
        }

        tolerance       1e-08;
        relTol          0;
        maxIter         20;
    }

    U
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        tolerance       1e-06;
        relTol          0;
        nSweeps         1;
    }

    Ue
    {
        solver		 PCG;
        preconditioner   DIC;
        tolerance        1e-14;
        relTol           0.0;
    };

    UeFinal
    {
        solver		 PCG;
        preconditioner   DIC;
        tolerance        1e-14;
        relTol           0.0;
    };

    rhoE
    {
        solver		 PBiCG;
        preconditioner   DILU;
        tolerance        1e-14;
        relTol           0.000;
    };

    rhoEFinal
    {
        solver		 PBiCG;
        preconditioner   DILU;
        tolerance        1e-14;
        relTol           0.000;
    };

    "(k|B|nuTilda)"
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-08;
        relTol          0;
    }
}

PIMPLE
{
    momentumPredictor no;
    nCorrectors     3;
    nNonOrthogonalCorrectors 0;
    nAlphaCorr      1;
    nAlphaSubCycles 3;
    cAlpha          1;

    pRefPoint      (0 5e-5 1e-5);
    pRefValue      0;
}

I am running this case on parallel but did not have issues while running it for lower conductivity.

Similarly, I tried using PCG solver in fvSolution but similar deltaT : 1e-81

Code:

solvers
{
    "alpha.water.*"
    {
        nAlphaCorr      2;
        nAlphaSubCycles 1;
        cAlpha          1;

       // MULESCorr       yes;
       // nLimiterIter    3;

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

     "pcorr.*"
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance       1e-5;
        relTol          0;
    }

    p_rgh
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance       1e-07;
        relTol          0.05;
    }

    p_rghFinal
    {
        $p_rgh;
        relTol          0;
    }

    U
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        tolerance       1e-06;
        relTol          0;
        nSweeps         1;
    }

    Ue
    {
        solver		 PCG;
        preconditioner   DIC;
        tolerance        1e-14;
        relTol           0.0;
    };

    UeFinal
    {
        solver		 PCG;
        preconditioner   DIC;
        tolerance        1e-14;
        relTol           0.0;
    };

    rhoE
    {
        solver		 PBiCG;
        preconditioner   DILU;
        tolerance        1e-14;
        relTol           0.000;
    };

    rhoEFinal
    {
        solver		 PBiCG;
        preconditioner   DILU;
        tolerance        1e-14;
        relTol           0.000;
    };

    "(k|B|nuTilda)"
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-08;
        relTol          0;
    }
}

PIMPLE
{
    momentumPredictor no;
    nCorrectors     3;
    nNonOrthogonalCorrectors 0;
    nAlphaCorr      1;
    nAlphaSubCycles 3;
    cAlpha          1;

    pRefPoint      (0 5e-5 1e-5);
    pRefValue      0;
}

mcfdma · November 3, 2020, 06:46

2D axisymmetric case and these are my boundary conditions:

alpha

Code:

dimensions      [0 0 0 0 0 0 0];


internalField   uniform 0;

boundaryField
{
    axis
    {
        type            empty;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 1;
    }
    nozzleWalls
    {
        type            zeroGradient;
    }
    atmosphere
    {
        type            inletOutlet;
        inletValue      uniform 0;
        value           uniform 0;
    }
    domainWall
    {
        type            zeroGradient;
    }
    floor
    {
        type            zeroGradient;
    }
    front
    {
        type            wedge;
    }
    back
    {
        type            wedge;
    }
}

p_rgh

Code:

dimensions      [1 -1 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    inlet 
    {
        type            zeroGradient;
    }
    nozzleWalls
    {
        type            zeroGradient;
    }
    atmosphere
    {
         type           totalPressure;
        p0              uniform 0;
    }
    domainWall
    {
        type            totalPressure;
        p0              uniform 0;
    }
    floor
    {
        type            zeroGradient;
    }
    axis
    {
        type            empty;
    }
    front
    {
        type            wedge;
    }
    back
    {
        type            wedge;
    }
}

rhoE

Code:

dimensions      [0 -3 1 0 0 1 0];

internalField   uniform 0;

boundaryField
{
    inlet 
    {
        type            zeroGradient;
    }
    nozzleWalls
    {
        type            zeroGradient;
    }
    atmosphere
    {
        type            zeroGradient;
    }domainWall
    {
        type            zeroGradient;
    }
    floor
    {
        type            zeroGradient;
    }
    axis
    {
        type            empty;
    }
    front
    {
        type            wedge;
    }
    back
    {
        type            wedge;
    }
}

U

Code:

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    inlet
    {
        type		fixedValue;
        value		uniform (0.00194 0 0);
    }
    nozzleWalls
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    atmosphere
    {
        type            zeroGradient;
    }
    domainWall
    {
        type            zeroGradient;
    }
    floor
    {
        type            zeroGradient;
    }
    axis
    {
        type            empty;
    }
    front
    {
        type            wedge;
    }
    back
    {
        type            wedge;
    }
}

Ue

Code:

dimensions      [1 2 -3 0 0 -1 0];

internalField   uniform 0;

boundaryField
{
    inlet 
    {
        type            zeroGradient;
    }
    nozzleWalls
    {
       type            fixedValue;
        value           uniform 4500;
    }
    atmosphere
    {
        type            zeroGradient;
    }
    domainWall
    {
        type            zeroGradient;
    }
    floor
    {
        type            fixedValue;
        value           uniform 0;
    }



    axis
    {
        type            empty;
    }
    front
    {
        type            wedge;
    }
    back
    {
        type            wedge;
    }
}

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