[swahono]

Hi All,

I am simulating a pipe with sudden expansion with a parabolic inlet velocity using simpleFoam.

The simulation started with laminar for 2000 iterations (residuals flat off after this) - solution attached.

Centreline Inlet Velocity is 0.178 m/s. Re_D=40,750.
GroovyBC was used to set the parabolic inlet velocity profile.

Then I restarted the simulation using RNGKEpsilon model.
The simulation crashed after 2 iterations! Consistently.
Error message indicate divide by zero problem for k and epsilon (See below).

Please NOTE that if I use NON-parabolic inlet (i.e. fixedValue), everything is fine - I got a good converged solution.

I used Upwind Div scheme with cellLimited interpolation scheme.
I have tried both PCG and GAMG for pressure, and PBiCG and GAMG for U|k|epsilon.
I have also tried varying URF.

I suspect the problem is in my BCs and bad starting solution for k and epsilon (since the flow is now parabolic from the inlet).
But, I can't figure out. I've also tried setting parabolic inlet profiles for k and epsilon to no avail.

Please Help anyone!.

the 0/epsilon:

inlet
{
type turbulentMixingLengthDissipationRateInlet;
mixingLength 0.05;
value uniform 1e-06;
}

the 0/k:

inlet
{
type turbulentIntensityKineticEnergyInlet;
intensity 0.05;
value uniform 0.0001;
}

Thank you very much.
I hope I do get any help this time.
Please.. It's quite difficult to get help from this forum.

Regards,
Stefano

Time = 2

DILUPBiCG:  Solving for Ux, Initial residual = 0.00855909, Final residual = 7.45812e-10, No Iterations 17
DILUPBiCG:  Solving for Uy, Initial residual = 0.0467024, Final residual = 6.71306e-10, No Iterations 17
DILUPBiCG:  Solving for Uz, Initial residual = 0.0490525, Final residual = 5.95911e-10, No Iterations 18
GAMG:  Solving for p, Initial residual = 0.192423, Final residual = 8.18271e-11, No Iterations 40
GAMG:  Solving for p, Initial residual = 0.0344647, Final residual = 6.74495e-11, No Iterations 35
GAMG:  Solving for p, Initial residual = 0.0101951, Final residual = 7.61577e-11, No Iterations 32
time step continuity errors : sum local = 8.98665e-13, global = 1.02105e-14, cumulative = 6.25679e-15
[4] #0  Foam::error::printStack(Foam::Ostream&) in "/home/stefano/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libOpenFOAM.so"
[4] #1  Foam::sigFpe::sigFpeHandler(int) in "/home/stefano/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libOpenFOAM.so"
[4] #2  __restore_rt at sigaction.c:0
[4] #3  Foam::divide(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) in "/home/stefano/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libOpenFOAM.so"
[4] #4  void Foam::divide<Foam::fvPatchField, Foam::volMesh>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) in "/home/stefano/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libincompressibleRASModels.so"
[4] #5  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::operator/<Foam::fvPatchField, Foam::volMesh>(Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) in "/home/stefano/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libincompressibleRASModels.so"
[4] #6  Foam::incompressible::RASModels::RNGkEpsilon::correct() in "/home/stefano/OpenFOAM/OpenFOAM-1.7.0/lib/linux64GccDPOpt/libincompressibleRASModels.so"
[4] #7  main in "/home/stefano/OpenFOAM/OpenFOAM-1.7.0/applications/bin/linux64GccDPOpt/simpleFoam"
[4] #8  __libc_start_main in "/lib64/libc.so.6"
[4] #9  Foam::regIOobject::writeObject(Foam::IOstream::streamFormat, Foam::IOstream::versionNumber, Foam::IOstream::compressionType) const in "/home/stefano/OpenFOAM/OpenFOAM-1.7.0/applications/bin/linux64GccDPOpt/simpleFoam"