# convergence problem when use pisoFoam, LES for wind tunnel case

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 January 25, 2010, 09:48 convergence problem when use pisoFoam, LES for wind tunnel case #1 New Member   Forrest Join Date: Oct 2009 Posts: 15 Rep Power: 16 Hello foamers, I am using pisoFoam to model a wind tunnel case, wind blowing on a small building model, both internal and external flow are modelled. Now I am having convergence problem for this LES calculation. My mesh check results are show below (part I), I modified the les pitzDaily case for this. The calculation started ok, with Courant Number mean about 0.0021, relatively stable; Max: about 0.5, changes can be from 0.25 to 0.6 normally. Time step is 0.00001s. However, after certain timesteps, the max Courant number starts increasing gradually, after another 100 timesteps or so, all of sudden, increased to a ridiculously big number and the calculation stopped (part II shows a few time step histories). My fvScheme and fvSolution are the same as the example. Can anyone suggest me how I should manage the convergence or give me some hints where the underlying problem might be? Your comments would be much appreciated, thank you. Regards Forrest ----------------- part I start -------------------- Checking geometry... Overall domain bounding box (-3.5 -5.3758e-17 -2.77785e-07) (2.48154e-24 0.8 1.2) Mesh (non-empty, non-wedge) directions (1 1 1) Mesh (non-empty) directions (1 1 1) Boundary openness (5.34441e-16 1.61725e-15 -2.62598e-15) OK. Max cell openness = 3.46613e-16 OK. Max aspect ratio = 76.0056 OK. Minumum face area = 2.07154e-07. Maximum face area = 0.000917946. Face area magnitudes OK. Min volume = 1.33381e-10. Max volume = 1.35026e-05. Total volume = 3.35384. Cell volumes OK. Mesh non-orthogonality Max: 61.7856 average: 2.95921 Non-orthogonality check OK. Face pyramids OK. Max skewness = 1.77896 OK. Mesh OK. ------------- part I ends -------------------------------------- ---------------- part II starts ----------------------------------- Time = 0.01271 Courant Number mean: 0.0020937 max: 0.266211 DILUPBiCG: Solving for Ux, Initial residual = 4.63219e-05, Final residual = 1.43073e-08, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.000157491, Final residual = 8.43967e-08, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.000339904, Final residual = 1.80376e-07, No Iterations 1 DICPCG: Solving for p, Initial residual = 0.00747972, Final residual = 0.000328662, No Iterations 4 time step continuity errors : sum local = 7.98063e-11, global = 1.06981e-13, cumulative = -7.66251e-10 DICPCG: Solving for p, Initial residual = 0.000495298, Final residual = 9.54513e-07, No Iterations 467 time step continuity errors : sum local = 2.31815e-13, global = -1.41083e-14, cumulative = -7.66265e-10 ExecutionTime = 12257.6 s ClockTime = 13416 s Calculating averages Time = 0.01272 Courant Number mean: 0.0020937 max: 0.279225 DILUPBiCG: Solving for Ux, Initial residual = 4.63096e-05, Final residual = 1.41444e-08, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.000157573, Final residual = 8.37715e-08, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.000340056, Final residual = 1.79683e-07, No Iterations 1 DICPCG: Solving for p, Initial residual = 0.00741885, Final residual = 0.000310164, No Iterations 4 time step continuity errors : sum local = 7.53338e-11, global = -1.02461e-13, cumulative = -7.66368e-10 DICPCG: Solving for p, Initial residual = 0.000466498, Final residual = 9.82048e-07, No Iterations 641 time step continuity errors : sum local = 2.38588e-13, global = -4.89605e-15, cumulative = -7.66373e-10 ExecutionTime = 12267.1 s ClockTime = 13426 s Calculating averages Time = 0.01273 Courant Number mean: 0.00209371 max: 0.29519 DILUPBiCG: Solving for Ux, Initial residual = 4.63311e-05, Final residual = 1.40266e-08, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.000157646, Final residual = 8.33521e-08, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.000340203, Final residual = 1.7883e-07, No Iterations 1 DICPCG: Solving for p, Initial residual = 0.00741554, Final residual = 0.000318821, No Iterations 4 time step continuity errors : sum local = 7.74663e-11, global = 2.24895e-14, cumulative = -7.6635e-10 DICPCG: Solving for p, Initial residual = 0.00047017, Final residual = 9.70856e-07, No Iterations 671 time step continuity errors : sum local = 2.35942e-13, global = 9.8275e-16, cumulative = -7.66349e-10 ExecutionTime = 12279.6 s ClockTime = 13438 s Calculating averages Time = 0.01274 Courant Number mean: 0.00209371 max: 0.310313 DILUPBiCG: Solving for Ux, Initial residual = 4.63345e-05, Final residual = 1.3925e-08, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.000157711, Final residual = 8.3139e-08, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 0.000340355, Final residual = 1.78012e-07, No Iterations 1 DICPCG: Solving for p, Initial residual = 0.00746455, Final residual = 0.000292083, No Iterations 4 time step continuity errors : sum local = 7.09822e-11, global = 3.03319e-15, cumulative = -7.66346e-10 DICPCG: Solving for p, Initial residual = 0.00044284, Final residual = 9.93709e-07, No Iterations 696 time step continuity errors : sum local = 2.41554e-13, global = -8.10546e-15, cumulative = -7.66354e-10 ExecutionTime = 12288 s ClockTime = 13447 s Time = 0.01358 Courant Number mean: 0.0020944 max: 1.09555 DILUPBiCG: Solving for Ux, Initial residual = 0.000104529, Final residual = 7.40216e-07, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.00017705, Final residual = 5.41423e-07, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.000381853, Final residual = 5.9746e-07, No Iterations 2 DICPCG: Solving for p, Initial residual = 0.0315146, Final residual = 0.00132091, No Iterations 23 time step continuity errors : sum local = 3.94768e-10, global = -2.34649e-11, cumulative = -8.9372e-10 DICPCG: Solving for p, Initial residual = 0.011235, Final residual = 9.56973e-07, No Iterations 832 time step continuity errors : sum local = 2.89374e-13, global = -4.59523e-16, cumulative = -8.93721e-10 ExecutionTime = 13071.6 s ClockTime = 14336 s Time = 0.01362 Courant Number mean: 0.00209513 max: 43.2669 DILUPBiCG: Solving for Ux, Initial residual = 0.000144988, Final residual = 3.94422e-06, No Iterations 8 DILUPBiCG: Solving for Uy, Initial residual = 0.000336237, Final residual = 8.91802e-06, No Iterations 10 DILUPBiCG: Solving for Uz, Initial residual = 0.000505316, Final residual = 3.00939e-06, No Iterations 9 DICPCG: Solving for p, Initial residual = 0.285304, Final residual = 0.012613, No Iterations 35 time step continuity errors : sum local = 7.27789e-09, global = 2.86231e-10, cumulative = -7.53916e-10 DICPCG: Solving for p, Initial residual = 0.912345, Final residual = 9.96687e-07, No Iterations 954 time step continuity errors : sum local = 5.17998e-12, global = 1.19195e-14, cumulative = -7.53904e-10 ExecutionTime = 13122.4 s ClockTime = 14387 s Time = 0.01367 Courant Number mean: 5.96862e+42 max: 3.76343e+48 DILUPBiCG: Solving for Ux, Initial residual = 0.994552, Final residual = 0.994644, No Iterations 1001 DILUPBiCG: Solving for Uy, Initial residual = 0.990671, Final residual = 0.990675, No Iterations 1001 DILUPBiCG: Solving for Uz, Initial residual = 0.997551, Final residual = 0.997559, No Iterations 1001 DICPCG: Solving for p, Initial residual = 1, Final residual = 20.1103, No Iterations 1001 time step continuity errors : sum local = 7.60816e+75, global = -6.40177e+66, cumulative = -6.40177e+66 DICPCG: Solving for p, Initial residual = 2.32194e-14, Final residual = 2.32194e-14, No Iterations 0 time step continuity errors : sum local = 4.07068e+76, global = -1.31145e+70, cumulative = -1.31209e+70 -------------------------- part II ends --------------------------

 July 14, 2011, 14:00 #2 Member   Join Date: Jul 2010 Posts: 52 Rep Power: 16 Did you find the solution to your problem?

July 15, 2011, 04:17
#3
New Member

Forrest
Join Date: Oct 2009
Posts: 15
Rep Power: 16
Quote:
 Originally Posted by MaryBau Did you find the solution to your problem?
That was long time ago and I haven't been working with openfoam for more than a year. If I remember correctly, the problem might have been the mesh, after conversion (I have to make the mesh using ICEM, save it as 'fluent' format, then convert using the tool provided by openfoam), something went wrong although the mesh checking wasn't able to pick up.

Sorry for not being helpful on this, good luck!

Forrest

 July 19, 2011, 06:00 convergence problem with pisoFoam #4 New Member   MA Lorin Join Date: May 2011 Location: France Posts: 6 Rep Power: 15 Hi foamers, I'm running a case of a steady flow around a foil (NACA 312 66) in 2D. I've some issues with the simpleFoam solver with k omega SST turbulence model. The calculation does not stop but values are totally false. So I try to run the case with pisoFoam and I've this error message Time = 0.0001 Courant Number mean: 0.456197 max: 236.765 DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 3.42308e-07, No Iterations 3 DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 5.55072e-06, No Iterations 2 DICPCG: Solving for p, Initial residual = 1, Final residual = 0.092087, No Iterations 304 time step continuity errors : sum local = 5.94242e-06, global = 5.46953e-08, cumulative = 5.46953e-08 DICPCG: Solving for p, Initial residual = 0.116726, Final residual = 9.73547e-07, No Iterations 432 time step continuity errors : sum local = 1.10727e-09, global = -3.54505e-12, cumulative = 5.46917e-08 #0 Foam::error:rintStack(Foam::Ostream&) in "/usr/OpenFOAM/OpenFOAM-1.7.1/lib/linux64GccDPOpt/libOpenFOAM.so" #1 Foam::sigFpe::sigFpeHandler(int) in "/usr/OpenFOAM/OpenFOAM-1.7.1/lib/linux64GccDPOpt/libOpenFOAM.so" #2 __restore_rt at sigaction.c:0 #3 Foam::LimitedScheme, Foam::limitFuncs::magSqr>::limiter(Foam::Geometric Field const&) const in "/usr/OpenFOAM/OpenFOAM-1.7.1/lib/linux64GccDPOpt/libfiniteVolume.so" #4 Foam::limitedSurfaceInterpolationScheme::w eights(Foam::GeometricField const&) const in "/usr/OpenFOAM/OpenFOAM-1.7.1/lib/linux64GccDPOpt/libfiniteVolume.so" #5 Foam::fv::gaussConvectionScheme::fvmDiv(Fo am::GeometricField const&, Foam::GeometricField&) const in "/usr/OpenFOAM/OpenFOAM-1.7.1/lib/linux64GccDPOpt/libfiniteVolume.so" #6 Foam::tmp > Foam::fvm::div(Foam::GeometricField const&, Foam::GeometricField&, Foam::word const&) in "/usr/OpenFOAM/OpenFOAM-1.7.1/lib/linux64GccDPOpt/libincompressibleRASModels.so" #7 Foam::tmp > Foam::fvm::div(Foam::GeometricField const&, Foam::GeometricField&) in "/usr/OpenFOAM/OpenFOAM-1.7.1/lib/linux64GccDPOpt/libincompressibleRASModels.so" #8 Foam::incompressible::RASModels::kOmegaSST::correc t() in "/usr/OpenFOAM/OpenFOAM-1.7.1/lib/linux64GccDPOpt/libincompressibleRASModels.so" #9 main in "/usr/OpenFOAM/OpenFOAM-1.7.1/applications/bin/linux64GccDPOpt/pisoFoam" #10 __libc_start_main in "/lib64/libc.so.6" #11 Foam::regIOobject::writeObject(Foam::IOstream::str eamFormat, Foam::IOstream::versionNumber, Foam::IOstream::compressionType) const in "/usr/OpenFOAM/OpenFOAM-1.7.1/applications/bin/linux64GccDPOpt/pisoFoam" Can you help me ?? I've run exactly the same case with simpleFoam and Spalart Allmaras and the results were quite good, but I need the results with K omega SST turbulence model to validate the case ! Thanks in advance ! MA