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Old   October 24, 2012, 13:48
Default convergence problem
  #1
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Hi,
I am having convergence problems with an old OF 1.6 case ported to OF 2.0. I am using snappyHexMesh to mesh a terrain ,then do a simpleFoam run. Maybe it is better to start from the new tutorial cases from scratch, but I seem to have done most of the porting right since it does the first iteration correct but it breaks on 2nd iteration. How can I track down such kind of errors ?
-------------
Create time

Create mesh for time = 0

Reading field p

Reading field U

Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian
Selecting RAS turbulence model kEpsilon
kEpsilonCoeffs
{
Cmu 0.03;
C1 1.21;
C2 1.92;
C3 -0.33;
sigmak 1;
sigmaEps 1.3;
Prt 1;
}


SIMPLE: convergence criteria
field p tolerance 1e-06
field U tolerance 1e-06
field "(k|epsilon)" tolerance 1e-06


Starting time loop

Time = 1

smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 0.00638534994837, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 0.0944616607626, No Iterations 10
smoothSolver: Solving for Uz, Initial residual = 1, Final residual = 0.00153355776121, No Iterations 1
GAMG: Solving for p, Initial residual = 1, Final residual = 0.0706871993687, No Iterations 2
time step continuity errors : sum local = 0.00244453565105, global = -0.00069856211074, cumulative = -0.00069856211074
smoothSolver: Solving for epsilon, Initial residual = 0.818403563622, Final residual = 0.0533243569086, No Iterations 2
smoothSolver: Solving for k, Initial residual = 0.999999999999, Final residual = 0.087750879704, No Iterations 2
ExecutionTime = 5.07 s ClockTime = 7 s

Time = 2

#0 Foam::error:rintStack(Foam::Ostream&) in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2 in "/lib64/libc.so.6"
#3 Foam::GaussSeidelSmoother::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) in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#4 Foam::GaussSeidelSmoother::smooth(Foam::Field<doub le>&, Foam::Field<double> const&, unsigned char, int) const in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#5 Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#6
in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/bin/simpleFoam"
#7
in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/bin/simpleFoam"
#8
in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/bin/simpleFoam"
#9 __libc_start_main in "/lib64/libc.so.6"
#10 Foam::UOPstream::write(char) in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/bin/simpleFoam"
Floating point exception
----------------------

Thanks
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Old   October 25, 2012, 05:44
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  #2
thg
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Thorsten Grahs
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Hi Besh,

like you see in your error message you got a problem with
a floating Point exception or with the signal handler for this

try

unset FOAM_SIGFPE

in your terminal where you running or maybe better
unset this in your

$WM_PROJECT_DIR/etc/bashrc
or
$WM_PROJECT_DIR/etc/cshrc

depending which shell your using. You have to source this file in advance before
running the solver again.
Regarding the SIGFPE error you find lots of post in this forum.

Best regards
Th.
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Old   October 25, 2012, 08:49
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Hi Thorsten,
Thank you very much! Now the floating point exception is gone and I can see it did not converge starting from the second iteration. I am starting from a case somebody used in his thesis in this forum (Benjamin Martinez) to simulate a 3D bump. He used an older version of OF and I am unable to run that even on a flat terrain (no snappyHex problems), so maybe something is wrong with my boundary conditions. If someone can look at my case file I attached here, I appreciate it very much. I will try to start modify the motorbike case of the tutorial.

Commands I used:

blockMesh
snappyHexMesh -overwrite (optional in case of flat terrain)
simpleFoam


Output:

------------------
Time = 1

smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 0.0973740880192, No Iterations 88
smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 0.0909104674317, No Iterations 4
smoothSolver: Solving for Uz, Initial residual = 1, Final residual = 0.0996167376728, No Iterations 36
GAMG: Solving for p, Initial residual = 1, Final residual = 0.0370515011559, No Iterations 2
time step continuity errors : sum local = 9.84275506881e-05, global = -2.30131469339e-05, cumulative = -2.30131469339e-05
smoothSolver: Solving for epsilon, Initial residual = 0.0948138314381, Final residual = 0.00874463076989, No Iterations 15
smoothSolver: Solving for k, Initial residual = 0.999999999999, Final residual = 0.0946209995768, No Iterations 31
ExecutionTime = 8.66 s ClockTime = 21 s

Time = 2

smoothSolver: Solving for Ux, Initial residual = 0.81429606278, Final residual = nan, No Iterations 1000
smoothSolver: Solving for Uy, Initial residual = 0.810558444421, Final residual = nan, No Iterations 1000
smoothSolver: Solving for Uz, Initial residual = 0.754355463774, Final residual = nan, No Iterations 1000
GAMG: Solving for p, Initial residual = nan, Final residual = nan, No Iterations 1000
time step continuity errors : sum local = nan, global = -nan, cumulative = -nan
smoothSolver: Solving for epsilon, Initial residual = nan, Final residual = nan, No Iterations 1000
smoothSolver: Solving for k, Initial residual = nan, Final residual = nan, No Iterations 1000
ExecutionTime = 90.07 s ClockTime = 105 s
------------------

Thank you
Attached Files
File Type: zip hill.zip (91.1 KB, 1 views)

Last edited by besh; October 25, 2012 at 09:51.
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Old   October 25, 2012, 12:07
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Quote:
I will try to start modify the motorbike case of the tutorial.
Modifying the turbinesitting tutorial with my terrain worked! I don't know what was wrong with one I took from 3Dbump case of Benjamin. Also the turbinesitting has everything perfectly setup including unsetting floating exceptions. Well the lesson i.e to always start from tut cases is learned.
Thanks a lot
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