# alpha value negative

 Register Blogs Members List Search Today's Posts Mark Forums Read

May 18, 2018, 03:29
alpha value negative
#1
Member

sabrina carson
Join Date: Apr 2016
Posts: 45
Rep Power: 7
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&, Foam::Field&, Foam::lduMatrix const&, Foam::FieldField const&, Foam::UPtrList const&, Foam::Field const&, unsigned char) const at ??:? #4 Foam::GAMGSolver::Vcycle(Foam::PtrList const&, Foam::Field&, Foam::Field const&, Foam::Field&, Foam::Field&, Foam::Field&, Foam::PtrList >&, Foam::PtrList >&, unsigned char) const at ??:? #5 Foam::GAMGSolver::solve(Foam::Field&, Foam::Field const&, unsigned char) const at ??:? #6 Foam::fvMatrix::solveSegregated(Foam::dict ionary const&) at ??:? #7 Foam::fvMatrix::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;
}

{
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;
}

laplacianSchemes
{
default         Gauss linear corrected;
}

interpolationSchemes
{
default         linear;
}

{
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;
}
{
solver           PBiCG;
preconditioner   DILU;
tolerance        1e-10;
relTol           0;
};

{
solver           PBiCG;
preconditioner   DILU;
tolerance        1e-10;
relTol           0;
}; */

"(T|TFinal)"
{
solver           PBiCG;
preconditioner   DILU;
tolerance        1e-10;
relTol           0;
};

{
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;
}```

 May 18, 2018, 08:46 #2 Member   sabrina carson Join Date: Apr 2016 Posts: 45 Rep Power: 7 I got the solution. I just reduced the value of deltaT from 0.001 to 0.000001.