# convergence problem

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

 October 24, 2012, 12:48 convergence problem #1 New Member   Join Date: Oct 2012 Posts: 15 Rep Power: 4 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&, Foam::lduMatrix const&, Foam::Field const&, Foam::FieldField const&, Foam::UPtrList const&, unsigned char, int) in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" #4 Foam::GaussSeidelSmoother::smooth(Foam::Field&, Foam::Field const&, unsigned char, int) const in "/work/dabdi3/OpenFOAM/OpenFOAM-2.0.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" #5 Foam::smoothSolver::solve(Foam::Field&, Foam::Field 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

 October 25, 2012, 04:44 #2 Member   Thorsten Grahs Join Date: Oct 2009 Posts: 44 Rep Power: 7 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.

October 25, 2012, 07:49
#3
New Member

Join Date: Oct 2012
Posts: 15
Rep Power: 4
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
 hill.zip (91.1 KB, 1 views)

Last edited by besh; October 25, 2012 at 08:51.

October 25, 2012, 11:07
#4
New Member

Join Date: Oct 2012
Posts: 15
Rep Power: 4
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

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Forrest_Lei OpenFOAM 3 July 19, 2011 06:00 commonyue Main CFD Forum 1 December 1, 2009 04:54 nasdak CFX 2 June 29, 2009 01:17 Emily FLUENT 2 March 21, 2007 23:18 Balraj Main CFD Forum 3 December 9, 2004 01:24

All times are GMT -4. The time now is 18:25.