[1988]

hi Formers
I am using IcoFoam solver and I didn't have any problem but as soon as scaling the geometry to millimeter I have got this error during processing.

Time = 0.006

Courant Number mean: 4.75321e+76 max: 3.75818e+81
DILUPBiCG:  Solving for Ux, Initial residual = 0.999964, Final residual = 1.021, No Iterations 1001
DILUPBiCG:  Solving for Uy, Initial residual = 0.999977, Final residual = 1.08934, No Iterations 1001
DILUPBiCG:  Solving for Uz, Initial residual = 0.999987, Final residual = 1.05489, No Iterations 1001
DICPCG:  Solving for p, Initial residual = 1, Final residual = 2.87353, No Iterations 1001
DICPCG:  Solving for p, Initial residual = 4.77489e-26, Final residual = 4.77489e-26, No Iterations 0
DICPCG:  Solving for p, Initial residual = 4.77489e-26, Final residual = 4.77489e-26, No Iterations 0
time step continuity errors : sum local = 7.20173e+114, global = 3.05681e+97, cumulative = 3.05681e+97
DICPCG:  Solving for p, Initial residual = 2.08226e-25, Final residual = 2.08226e-25, No Iterations 0
DICPCG:  Solving for p, Initial residual = 2.08226e-25, Final residual = 2.08226e-25, No Iterations 0
DICPCG:  Solving for p, Initial residual = 2.08226e-25, Final residual = 2.08226e-25, No Iterations 0
time step continuity errors : sum local = 3.14056e+115, global = -4.27954e+98, cumulative = -3.97386e+98
ExecutionTime = 869.68 s  ClockTime = 874 s

Time = 0.007

Courant Number mean: 3.30783e+115 max: 3.16723e+119
[0] #0  [1] #0  Foam::error::printStack(Foam::Ostream&)Foam::error::printStack(Foam::Ostream&) at ??:?
[0] #1  Foam::sigFpe::sigHandler(int) at ??:?
[1] #1  Foam::sigFpe::sigHandler(int) at ??:?
[0] #2  Uninterpreted: 
[0] #3   at ??:?
[1] #2  Uninterpreted: 
[1] #3   in "/usr/lib/libmpi.so.0"
[0] #4   in "/usr/lib/libmpi.so.0"
[1] #4   in  in "/usr/lib/openmpi/lib/openmpi/mca_coll_tuned.so"
[1] #5  "/usr/lib/openmpi/lib/openmpi/mca_coll_tuned.so"
[0] #5   in "/usr/lib/openmpi/lib/openmpi/mca_coll_tuned.so"
[1] #6  PMPI_Allreduce in "/usr/lib/openmpi/lib/openmpi/mca_coll_tuned.so"
[0] #6  PMPI_Allreduce in "/usr/lib/libmpi.so.0"
[1] #7  void Foam::allReduce<double, Foam::sumOp<double> >(double&, int, ompi_datatype_t*, ompi_op_t*, Foam::sumOp<double> const&, int) in "/usr/lib/libmpi.so.0"
[0] #7  void Foam::allReduce<double, Foam::sumOp<double> >(double&, int, ompi_datatype_t*, ompi_op_t*, Foam::sumOp<double> const&, int) at ??:?
[1] #8  Foam::reduce(double&, Foam::sumOp<double> const&, int) at ??:?
[0] #8  Foam::reduce(double&, Foam::sumOp<double> const&, int) at ??:?
[1] #9   at ??:?
[0] #9  Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) constFoam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
[0] #10   at ??:?
[1] #10  

[0]  at ??:?
[0] #11  [1]  at ??:?
[1] #11  

[0]  at ??:?
[0] #12  [1]  at ??:?
[1] #12  

[0]  at ??:?
[0] #13  [1]  at ??:?
[1] #13  

[0]  at ??:?
[0] #14  [1]  at ??:?
[1] #14  

[0]  at ??:?
[0] #15  __libc_start_main[1]  at ??:?
[1] #15  __libc_start_main in "/lib/i386-linux- in gnu/libc.so.6"
[0] #16  "/lib/i386-linux-gnu/libc.so.6"
[1] #16  

[1]  at ??:?

I have read this link but I could not find the solution

http://www.cfd-online.com/Forums/openfoam-solving/95674-high-courant-number-icofoam.html

this is checkMesh

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           302592
    faces:            885385
    internal faces:   864251
    cells:            291606
    faces per cell:   6
    boundary patches: 3
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     291606
    prisms:        0
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     0

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
    Patch               Faces    Points   Surface topology                  
    body                19650    19700    ok (non-closed singly connected)  
    inlet               742      768      ok (non-closed singly connected)  
    outlet              742      768      ok (non-closed singly connected)  

Checking geometry...
    Overall domain bounding box (-0.0142294 0 -0.0151572) (0.0129588 0.0472016 0.0022)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (3.0901e-17 -9.27854e-17 -1.34611e-16) OK.
    Max cell openness = 3.32518e-16 OK.
    Max aspect ratio = 9.66007 OK.
    Minimum face area = 8.65714e-10. Maximum face area = 8.93054e-08.  Face area magnitudes OK.
    Min volume = 2.58464e-13. Max volume = 1.87293e-11.  Total volume = 1.09182e-06.  Cell volumes OK.
    Mesh non-orthogonality Max: 24.5048 average: 5.06496
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.361877 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End

and this is the controldict file:

application     icoFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime       4.8;

deltaT          0.001;

writeControl    timeStep;

writeInterval  20;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

libs (
    "libOpenFOAM.so"
    "libgroovyBC.so"
) ;

fvSchemes(completely the same as fvscheme which had been defined in cavity folder)

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
    grad(p)         Gauss linear;
}

divSchemes
{
    default         none;
    div(phi,U)      Gauss linear;
}

laplacianSchemes
{
    default         none;
    laplacian(nu,U) Gauss linear orthogonal;
    laplacian((1|A(U)),p) Gauss linear orthogonal;
}

interpolationSchemes
{
    default         linear;
    interpolate(HbyA) linear;
}

snGradSchemes
{
    default         orthogonal;
}

fluxRequired
{
    default         no;
    p               ;
}

this is fvSolution again the same as cavity example \

solvers
{
    p
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance       1e-06;
        relTol          0;
    }

    U
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-05;
        relTol          0;
    }
}

PISO
{
    nCorrectors     2;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       0;
}

is there anyone who can give the solution?
thanks

[adambarfi]

your solution can't be converged because of your very high Courant Number,

Time = 0.007

Courant Number mean: 3.30783e+115 max: 3.16723e+119

the Courant number is:
CoNum = 0.5*gMax(sumPhi/mesh.V().field())*runTime.deltaTValue()

so,I think that your boundary conditions aren't match with your geometry dimensions. calculate your non-dimensional numbers and check where is the problem.

If they are reaonable for your problem, decrease the deltaT.

[1988]

there is no way to change the boundary conditions because the simulation become completely wrong so I cant do anything about boundaries meanwhile about time steps I have to mention that they are set to 0.001 second and the end time is 4.8 so reducing the quantity of time step would be so costly .there is no other way?