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alpha value negative

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Old   May 18, 2018, 03:29
Default alpha value negative
  #1
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Sabrina Carson
Join Date: Apr 2016
Posts: 25
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silviliril is on a distinguished road
Hi,

I am trying to simulate condensation problem using phaseChangeHeatFoam using Dynamic Mesh. But, I am getting following error. Where Value of alpha is going -751. WHich is non physical.

Quote:
Create time

Create mesh for time = 0.001

Selecting dynamicFvMesh dynamicRefineFvMesh
Reading field p_rgh

Reading field T

Reading field alpha1

Reading field U

Reading/calculating face flux field phi

Creating phaseChangeTwoPhaseMixture

Selecting phaseChange model Hardt
Selecting incompressible transport model Newtonian
Selecting incompressible transport model Newtonian
Selecting turbulence model type laminar

Reading g

Reading hRef
Calculating field g.h

No finite volume options present

Creating field kinetic energy K


PIMPLE: Operating solver in PISO mode

time step continuity errors : sum local = 0, global = 0, cumulative = 0
GAMGPCG: Solving for pcorr, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 0, global = 0, cumulative = 0
Courant Number mean: 0 max: 0

Starting time loop

Interface Courant Number mean: 0 max: 0
Courant Number mean: 0 max: 0
deltaT = 0.001
Time = 0.002

Selected 20000 cells for refinement out of 1285000.
Refined from 1285000 to 1425000 cells.
Selected 0 split points out of a possible 20000.
Execution time for mesh.update() = 9.29 s
time step continuity errors : sum local = 0.63639, global = 6.51141e-17, cumulative = 6.51141e-17
GAMGPCG: Solving for pcorr, Initial residual = 1, Final residual = 7.59271e-05, No Iterations 4
time step continuity errors : sum local = 4.83193e-05, global = -1.52192e-06, cumulative = -1.52192e-06
MULES: Solving for alpha1
Liquid phase volume fraction = 0.495664 Min(alpha1) = -751.483 Max(alpha1) = 616.829
MULES: Solving for alpha1
Liquid phase volume fraction = 0.746649 Min(alpha1) = -562573 Max(alpha1) = 570996
MULES: Solving for alpha1
Liquid phase volume fraction = -79.9499 Min(alpha1) = -1.04484e+09 Max(alpha1) = 4.82987e+08
DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 911.698, No Iterations 1001
DILUPBiCG: Solving for Uy, Initial residual = 0.918964, Final residual = 5515.72, No Iterations 1001
DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 49428.4, No Iterations 1001
#0 Foam::error:rintStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 Foam::GAMGSolver::scale(Foam::Field<double>&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::Field<double> const&, unsigned char) const at ??:?
#4 Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMa trix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const at ??:?
#5 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#6 Foam::fvMatrix<double>::solveSegregated(Foam::dict ionary const&) at ??:?
#7 Foam::fvMatrix<double>::solve(Foam::dictionary const&) at ??:?
#8
at ??:?
#9 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#10
at ??:?
Floating point exception (core dumped)
fvschemes:
Code:
Code:
ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    div(rho*phi,U)  Gauss upwind;
    div(rhoPhi,U)  Gauss vanLeerV;
    div(phi,T)  Gauss vanLeer;
    div(rhoPhi,T)    Gauss  vanLeer;
    div(phi,alpha)  Gauss vanLeer01;
    div(phirb,alpha) Gauss interfaceCompression;
    div((muEff*dev(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    p_rgh;
    pcorr;
    alpha;
}
fvsolution:
Code:
solvers
{

    alpha1
    {
        maxUnboundedness 1e-5;
        CoCoeff          2;
        maxIter          5;
        nLimiterIter     2;
        solver           PBiCG;
        preconditioner   DILU;
        tolerance        1e-12;
        relTol           0.01;
    };

 "(U|UFinal|T|TFinal)"
    {
        solver           PBiCG;
        preconditioner   DILU;
        tolerance        1e-06;
        relTol           0;
    };

 "(p_rgh|p)"
    {
        solver          PCG;     
	preconditioner 
        {
            preconditioner  GAMG;
            tolerance       1e-08;
            relTol          0;
            nVcycles        2;
            smoother        GaussSeidel;
            nPreSweeps      0;
            nPostSweeps     2;
            nFinestSweeps   2;
            cacheAgglomeration true;
            nCellsInCoarsestLevel 10;
            agglomerator    faceAreaPair;
            mergeLevels     1;
        }

        tolerance       1e-08;
        relTol          0.001;
        maxIter         20;
    };

    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;
    };

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

    p_rgh
    {
        solver          GAMG;
        tolerance       1e-08;
        relTol          0.05;
        smoother        GaussSeidel;
        nPreSweeps      0;
        nPostSweeps     2;
        nFinestSweeps   2;
        cacheAgglomeration true;
        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 true;
            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;
    }

    "(k|B|nuTilda)"
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-08;
        relTol          0;
    }
  /* T   //add
    {
        solver           PBiCG;
        preconditioner   DILU;
        tolerance        1e-10;
        relTol           0;
    };

  /*TFinal   //added
    {
        solver           PBiCG;
        preconditioner   DILU;
        tolerance        1e-10;
        relTol           0;
    }; */
  
  "(T|TFinal)" 
    {
        solver           PBiCG;
        preconditioner   DILU;
        tolerance        1e-10;
        relTol           0;
    }; 
 
    rho   //add
    {
        solver           Diagonal;
        tolerance        1e-8;
        relTol           0;
    };
}

relaxationFactors
{
    T       0.3
    U       0.3
    p       0.3;
}

"(PISO|PIMPLE)"
{
    momentumPredictor yes;
    nCorrectors     3;
    nNonOrthogonalCorrectors 0;
    nAlphaCorr      1;
    nAlphaSubCycles 3;
    cAlpha          1;

    pRefPoint      (0.51 0.51 0.51);
    pRefValue      0;
 smoothItr                  2;
    kSmoothItr                 0;
}
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Old   May 18, 2018, 08:46
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  #2
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Sabrina Carson
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Posts: 25
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I got the solution. I just reduced the value of deltaT from 0.001 to 0.000001.
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