0
Simulation error (delta T is decreasing while the iterations are being carried out)

Courant Number mean: 0.0163613 max: 1.00448
Interface Courant Number mean: 0.00015773 max: 0.241142
deltaT = 0.000254916
Time = 0.00156593

PIMPLE: iteration 1
smoothSolver:  Solving for alpha.liquid, Initial residual = 0.00160927, Final residual = 2.5586e-10, No Iterations 2
Phase-1 volume fraction = 0.0170806  Min(alpha.liquid) = -3.07529e-07  Max(alpha.liquid) = 0.999998
MULES: Correcting alpha.liquid
MULES: Correcting alpha.liquid
Phase-1 volume fraction = 0.0170806  Min(alpha.liquid) = -9.82735e-06  Max(alpha.liquid) = 0.999998
DILUPBiCG:  Solving for Ux, Initial residual = 0.0904852, Final residual = 4.99181e-06, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.0925329, Final residual = 3.61106e-06, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.0942319, Final residual = 3.21896e-06, No Iterations 1
GAMG:  Solving for p_rgh, Initial residual = 0.0101787, Final residual = 6.88573e-05, No Iterations 3
time step continuity errors : sum local = 1.45928e-06, global = 5.03199e-07, cumulative = -5.27753e-05
GAMG:  Solving for p_rgh, Initial residual = 0.00605928, Final residual = 6.59131e-09, No Iterations 13
time step continuity errors : sum local = 1.35045e-10, global = 3.61413e-11, cumulative = -5.27753e-05
ExecutionTime = 4.69 s  ClockTime = 5 s

Courant Number mean: 0.0161746 max: 2.52635
Interface Courant Number mean: 0.000154353 max: 0.657568
deltaT = 0.000100695
Time = 0.00166663
PIMPLE: iteration 1
smoothSolver:  Solving for alpha.liquid, Initial residual = 1.21772e-06, Final residual = 6.95791e-10, No Iterations 2
Phase-1 volume fraction = 0.0169872  Min(alpha.liquid) = -1.56426e-07  Max(alpha.liquid) = 0.999998
MULES: Correcting alpha.liquid
MULES: Correcting alpha.liquid
Phase-1 volume fraction = 0.0169872  Min(alpha.liquid) = -1.56426e-07  Max(alpha.liquid) = 0.999998
#0  Foam::error::printStack(Foam::Ostream&)                                                         at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ?     in "/home/kvk/OpenFOAM/OpenFOAM-3.0.1/platforms/linuxGccDPInt32Opt/lib/libOpenFOAM.so"
#3  Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#4                  ?     at ??:?
#5  ? at ??:?
#6  ? at ??:?
#7      ? at ??:?
#8  __libc_start_main in "/lib/i386-linux-gnu/libc.so.6"
#9      ? at ??:?



/*--------------------------------*- C++ -*----------------------------------*\\
| =========                 |                                                 |
| \\\\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\\\    /   O peration     | Version:  2.3.0                                 |
|   \\\\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\\\/     M anipulation  |                                                 |
\\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    "alpha.liquid.*"
    {
        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           GAMG;
    tolerance        1e-8;
    relTol           0.01;

    smoother         GaussSeidel;

    cacheAgglomeration true;
    nCellsInCoarsestLevel 10;
    agglomerator     faceAreaPair;
    mergeLevels      1;
    }

    p_rghFinal
    {
        $p_rgh;
        relTol          0;
    }

    "(U|k|epsilon).*"
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-5;
        relTol          0;
    }
}

PIMPLE
{
    momentumPredictor   yes;
    nOuterCorrectors    1;
    nCorrectors         2;
    nNonOrthogonalCorrectors 0;
}

relaxationFactors
{
    equations
    {
        ".*"                1;
    }
}

// ************************************************************************* //




OpenFOAM 13-03-16, 12:42 a.m. KVK

Answers:

0

Hi KVK,

Your deltaT is decreasing / changing because of implementation of adjustable Runtime in controlDict file which must have been kept on. Also please check your initial dT since your max Courant number ( Co = U*dT / dX ) is exceeding the limit value of 1.
Most of the times the solution diverges because of the Courant number exceeding 1 in such explicit solvers.
Try decreasing the initial  time step (dT).

Regards,

Rahul Joshi

13-03-16, 8:29 a.m. rahuljoshi

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     interFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         1;

deltaT          0.01;

writeControl    adjustableRunTime;

writeInterval   0.05;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

adjustTimeStep  on;

maxCo           1;
maxAlphaCo      1;

maxDeltaT       1;


// ************************************************************************* //


13-03-16, 10:44 a.m. KVK

can you tell me which one to change as i am a new bee to Open Foam . Thanks in advance


13-03-16, 10:46 a.m. KVK

Login to add comment


0

Hi KVK, 


Keep the adjust time step -  off

In case you keep it on,  keep the deltaT as 0.001 and then try running your simulation. 

13-03-16, 11:40 a.m. rahuljoshi

I have kept adjust time step -off  but the error still exists as shown below

PIMPLE: iteration 1
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in "/home/kvk/OpenFOAM/OpenFOAM-3.0.1/platforms/linuxGccDPInt32Opt/lib/libOpenFOAM.so"
#3  Foam::symGaussSeidelSmoother::smooth(Foam::word const&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::Field<double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, unsigned char, int) at ??:?
#4  Foam::symGaussSeidelSmoother::smooth(Foam::Field<double>&, Foam::Field<double> const&, unsigned char, int) const at ??:?
#5  Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#6  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) at ??:?
#7  Foam::fvMatrix<double>::solve(Foam::dictionary const&) at ??:?
#8  Foam::fvMatrix<double>::solve() at ??:?
#9  ? at ??:?
#10  __libc_start_main in "/lib/i386-linux-gnu/libc.so.6"
#11  ? at ??:?
Floating point exception (core dumped)
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     interFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         1;

deltaT          0.01;

writeControl    adjustableRunTime;

writeInterval   0.05;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

adjustTimeStep  off;

maxCo           1;
maxAlphaCo      1;

maxDeltaT       1;


// ************************************************************************* //



13-03-16, 11:51 a.m. KVK

Login to add comment


0

Hi KVK, 


Try couple things

1. Keep deltaT as e-5

2. Check for any variables if they are tending to zero. Floating point exception error can occur because of it. 



13-03-16, 11:59 a.m. rahuljoshi


0

Floating point error is nothing but some quantity being divided by zero and hence the solution with not proceed. 

13-03-16, 12:03 p.m. rahuljoshi

application     interFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         1;

deltaT          1e-5;

writeControl    adjustableRunTime;

writeInterval   0.05;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

adjustTimeStep  off;

maxCo           1;
maxAlphaCo      1;

maxDeltaT       1;


// ************************************************************************* //
solvers
{
    "alpha.liquid.*"
    {
        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           GAMG;
    tolerance        1e-8;
    relTol           0.01;

    smoother         GaussSeidel;

    cacheAgglomeration true;
    nCellsInCoarsestLevel 10;
    agglomerator     faceAreaPair;
    mergeLevels      1;
    }

    p_rghFinal
    {
        $p_rgh;
        relTol          0;
    }

    "(U|k|epsilon).*"
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-5;
        relTol          0;
    }
}

PIMPLE
{
    momentumPredictor   yes;
    nOuterCorrectors    1;
    nCorrectors         2;
    nNonOrthogonalCorrectors 1;
}

relaxationFactors
{
    equations
    {
        ".*"                1;
    }
}

// ************************************************************************* //


the above two are my control dict and fvsolution files. The simulation is ending abruptly at some time in middle as below

PIMPLE: iteration 1
smoothSolver:  Solving for alpha.liquid, Initial residual = 0.999986, Final residual = 9.2483e-09, No Iterations 138
Phase-1 volume fraction = -12.544  Min(alpha.liquid) = -29744.2  Max(alpha.liquid) = 12901
MULES: Correcting alpha.liquid
MULES: Correcting alpha.liquid
Phase-1 volume fraction = 3.36842e+08  Min(alpha.liquid) = -7.83255e+23  Max(alpha.liquid) = 5.35775e+23
DILUPBiCG:  Solving for Ux, Initial residual = 0.990449, Final residual = 3.42602e-06, No Iterations 17
DILUPBiCG:  Solving for Uy, Initial residual = 0.59579, Final residual = 7.36343e-06, No Iterations 30
DILUPBiCG:  Solving for Uz, Initial residual = 0.559222, Final residual = 9.83663e-06, No Iterations 26
GAMG:  Solving for p_rgh, Initial residual = 0.937128, Final residual = 0.00885738, No Iterations 12
GAMG:  Solving for p_rgh, Initial residual = 1.88765e-13, Final residual = 1.88765e-13, No Iterations 0
time step continuity errors : sum local = 6.226e+14, global = 6.33828e+07, cumulative = 6.33828e+07
GAMG:  Solving for p_rgh, Initial residual = 2.0819e-13, Final residual = 2.0819e-13, No Iterations 0
GAMG:  Solving for p_rgh, Initial residual = 2.0819e-13, Final residual = 2.0819e-13, No Iterations 0
time step continuity errors : sum local = 6.86671e+14, global = 6.33828e+07, cumulative = 1.26766e+08
ExecutionTime = 42.35 s  ClockTime = 42 s

Courant Number mean: 4.02428e+14 max: 1.20117e+19
Interface Courant Number mean: 7.47408e+10 max: 1.88614e+15
Time = 0.22

PIMPLE: iteration 1
smoothSolver:  Solving for alpha.liquid, Initial residual = 1.4338e-05, Final residual = 6.50799e-09, No Iterations 4
Phase-1 volume fraction = -2.49431e+25  Min(alpha.liquid) = -1.64242e+30  Max(alpha.liquid) = 5.05257e+27
MULES: Correcting alpha.liquid
MULES: Correcting alpha.liquid
Phase-1 volume fraction = -5.16478e+68  Min(alpha.liquid) = -2.12968e+91  Max(alpha.liquid) = 2.27409e+91
DILUPBiCG:  Solving for Ux, Initial residual = 0.920589, Final residual = 1.25686e+06, No Iterations 1001
DILUPBiCG:  Solving for Uy, Initial residual = 0.447941, Final residual = 2.59224, No Iterations 1001
DILUPBiCG:  Solving for Uz, Initial residual = 0.905685, Final residual = 548.417, No Iterations 1001
GAMG:  Solving for p_rgh, Initial residual = 1, Final residual = 0.00768092, No Iterations 1
GAMG:  Solving for p_rgh, Initial residual = 2.86325e-31, Final residual = 2.86325e-31, No Iterations 0
time step continuity errors : sum local = 6.73556e+81, global = 1.09815e+65, cumulative = 1.09815e+65
GAMG:  Solving for p_rgh, Initial residual = 2.86412e-31, Final residual = 2.86412e-31, No Iterations 0
GAMG:  Solving for p_rgh, Initial residual = 2.86412e-31, Final residual = 2.86412e-31, No Iterations 0
time step continuity errors : sum local = 6.7376e+81, global = 1.09761e+65, cumulative = 2.19576e+65
ExecutionTime = 64.39 s  ClockTime = 64 s

Courant Number mean: 3.36975e+81 max: 3.57268e+86
Interface Courant Number mean: 3.63838e+71 max: 3.74641e+76
Time = 0.23

PIMPLE: iteration 1
smoothSolver:  Solving for alpha.liquid, Initial residual = 3.64905e-48, Final residual = 3.64905e-48, No Iterations 0
Phase-1 volume fraction = -5.16478e+68  Min(alpha.liquid) = -2.12968e+91  Max(alpha.liquid) = 2.27409e+91
MULES: Correcting alpha.liquid
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in "/home/kvk/OpenFOAM/OpenFOAM-3.0.1/platforms/linuxGccDPInt32Opt/lib/libOpenFOAM.so"
#3  Foam::multiply(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4  void Foam::multiply<Foam::fvsPatchField, Foam::surfaceMesh>(Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh>&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&) at ??:?
#5  Foam::tmp<Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> > Foam::operator*<Foam::fvsPatchField, Foam::surfaceMesh>(Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::tmp<Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> > const&) at ??:?
#6  Foam::fv::gaussConvectionScheme<double>::flux(Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) const at ??:?
#7  ? at ??:?
#8  ? at ??:?
#9  __libc_start_main in "/lib/i386-linux-gnu/libc.so.6"
#10  ? at ??:?
Floating point exception (core dumped)
 



13-03-16, 12:29 p.m. KVK

Login to add comment


0

Your courant number exceeds 1.


Can you mail us  your case file on this mail I'd. 

contact_cfd@fossee.in

I will get back to you tomorrow.

13-03-16, 12:39 p.m. rahuljoshi

okay .


13-03-16, 12:42 p.m. KVK

Hello,


I am facing the same problem and I couldn't find a solution

this is my control dictionary

application     interFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         2;

deltaT          0.0001;

writeControl    adjustableRunTime;

writeInterval   0.05;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

adjustTimeStep  on;

maxCo           0.8;
maxAlphaCo      1;

maxDeltaT       0.01;

Any help please ???


12-10-16, 10:07 p.m. islem

Login to add comment


Log-in to answer to this question.