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September 19, 2021, 17:29 
Convergence problem of OF

#1 
Member
WY
Join Date: Mar 2020
Posts: 33
Rep Power: 4 
Hi, I have met a convergence problem in OF when simulating the FSI of cylinder. The CFL becomes larger until around 30,000 at the last timestep before crash. I also checked the pressure and velocity fields in Paraview and find they are obviously unreasonable at the very beginning.
The following is the error report: Code:
#0 Foam::error::printStack(Foam::Ostream&) at ??:? #1 Foam::sigFpe::sigHandler(int) at ??:? #2 ? in "/lib/x86_64linuxgnu/libc.so.6" #3 Foam::GAMGSolver::scale(Foam::Field<double>&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::Field<double> const&, unsigned char) const at ??:? #4 Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMatrix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const at ??:? #5 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:? #6 Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) at ??:? #7 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/ying/OpenFOAM41/OpenFOAM4.1/platforms/linux64GccDPInt32Opt/bin/pimpleDyMFoam" #8 ? in "/home/ying/OpenFOAM41/OpenFOAM4.1/platforms/linux64GccDPInt32Opt/bin/pimpleDyMFoam" #9 __libc_start_main in "/lib/x86_64linuxgnu/libc.so.6" #10 ? in "/home/ying/OpenFOAM41/OpenFOAM4.1/platforms/linux64GccDPInt32Opt/bin/pimpleDyMFoam" Floating point exception (core dumped) Foam::error::printStack(Foam::Ostream&) in "/opt/openfoam222/platforms/linux64GccDPOp https://www.simscale.com/forum/t/cfd...failing/82914 https://www.salomeplatform.org/foru...m_10/549857363 but very limited information can be obtained.... I use a refine mesh to rerun and the case can last for more time steps (coarse mesh crash at time = 1.8 and refine mesh crash at time=18) but U and P are still incorrect at the very beginning. The attachments include: (1) case.zip: 0.zip (U, p, pointDisplacement) system.zip (controlDict, fvScheme, fvSolution) constant.zip (dynamicMeshDict, transportProperties, turbulenceProperties) (2) log.zip (log.pimpleDyMFoam file) (3) coarse.zip (coarse mesh, and corresponding (U, p) images at last timestep) (4) refine.zip (refine mesh, and corresponding (U, p) images at last timestep) Due to the size limit, I cannot upload my mesh and animation of flow fields, please send me email if you want to obtain the complete case file. I am very appreciated for any suggestion! 

September 20, 2021, 02:39 

#2 
Member
Join Date: Feb 2020
Posts: 75
Rep Power: 4 
Hi,
Firstly, you should add maxDeltaT and maxCo in your controlDict to avoid any blow up of the time step. I suggest to test it and revert to us. Best Regards, 

September 20, 2021, 11:09 

#3  
Member
WY
Join Date: Mar 2020
Posts: 33
Rep Power: 4 
Quote:
Quote:
Actually, I originally set the adjustTimeStep as false and specify fixed deltaT, so the time step will not blow up. And I try to decrease deltaT but the case still crashes at very big CFL. For example, using the same mesh, the case crashes at time = 1.83 when deltaT = 0.01, crashes at time = 1.775 when deltaT = 0.005, crashes at time = 0.368 when deltaT = 0.001. According to your suggestion, I also use the adjustable timestep by adding the following 3 lines before function in the controlDict: Code:
adjustTimeStep on; maxCo 2; maxDeltaT 0.1; I also attach part of log.pimpleDyMFoam (due to size limit) here. Code:
Create time Create mesh for time = 0 Selecting dynamicFvMesh dynamicMotionSolverFvMesh Selecting motion solver: sixDoFRigidBodyMotion Selecting sixDoFSolver Newmark Translational constraint tensor (0 0 0 0 1 0 0 0 0) Rotational constraint tensor (0 0 0 0 0 0 0 0 0) PIMPLE: no residual control data found. Calculations will employ 2 corrector loops Reading field p Reading field U Reading/calculating face flux field phi Selecting incompressible transport model Newtonian Selecting turbulence model type laminar No MRF models present Reading/calculating face velocity Uf No finite volume options present Courant Number mean: 1.00047e05 max: 0.000610799 fieldAverage fieldAverage1: Starting averaging at time 0 forces forces: Not including porosity effects forces forceCoeffs: Not including porosity effects forceCoeffs forceCoeffs: Not including porosity effects Reading surface description: zNormal Starting time loop Courant Number mean: 1.00037e05 max: 0.000610738 deltaT = 0.00119976 Time = 0.00119976 forces forces: Not including porosity effects Restraint verticalSpring: attachmentPt  anchor (0 0 0) spring length 0 force (0 0 0) 6DoF rigid body motion Centre of rotation: (0.280485 0 0) Centre of mass: (0.280485 0 0) Orientation: (1 0 0 0 1 0 0 0 1) Linear velocity: (0 0 0) Angular velocity: (0 0 0) GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.0196279, No Iterations 12 GAMG: Solving for pcorr, Initial residual = 0.0199319, Final residual = 0.0199319, No Iterations 0 time step continuity errors : sum local = 6.71518e05, global = 6.13618e08, cumulative = 6.13618e08 PIMPLE: iteration 1 smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 1.45212e06, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 0.0300958, No Iterations 1 GAMG: Solving for p, Initial residual = 1, Final residual = 0.00738863, No Iterations 14 GAMG: Solving for p, Initial residual = 0.0194856, Final residual = 0.000119229, No Iterations 6 time step continuity errors : sum local = 4.03179e07, global = 7.0946e09, cumulative = 6.84564e08 GAMG: Solving for p, Initial residual = 0.0212682, Final residual = 0.00011576, No Iterations 14 GAMG: Solving for p, Initial residual = 0.0141619, Final residual = 8.47907e05, No Iterations 6 time step continuity errors : sum local = 2.89751e07, global = 5.20169e09, cumulative = 7.36581e08 PIMPLE: iteration 2 smoothSolver: Solving for Ux, Initial residual = 0.555428, Final residual = 1.10649e07, No Iterations 3 smoothSolver: Solving for Uy, Initial residual = 0.0382701, Final residual = 2.11528e07, No Iterations 3 GAMG: Solving for p, Initial residual = 0.0218124, Final residual = 0.000131796, No Iterations 14 GAMG: Solving for p, Initial residual = 0.0144855, Final residual = 8.75873e05, No Iterations 6 time step continuity errors : sum local = 2.98957e07, global = 5.5809e09, cumulative = 7.9239e08 GAMG: Solving for p, Initial residual = 0.00406269, Final residual = 3.32292e05, No Iterations 9 GAMG: Solving for p, Initial residual = 0.00199958, Final residual = 4.88785e08, No Iterations 17 time step continuity errors : sum local = 1.71296e10, global = 1.77625e12, cumulative = 7.92407e08 ExecutionTime = 0.81 s ClockTime = 1 s Reading/initialising field UMean Reading/initialising field pMean Reading/initialising field UPrime2Mean Reading/initialising field pPrime2Mean fieldAverage fieldAverage1 write: Calculating averages forces forces write: sum of forces: pressure : (2733.32 0.306721 2.04533e15) viscous : (12.2219 0.0430355 5.66497e16) porous : (0 0 0) sum of moments: pressure : (1.40488e15 3.03509e16 0.311642) viscous : (4.34042e16 2.32209e16 0.00189707) porous : (0 0 0) .... Courant Number mean: 0.0190881 max: 3.12244 deltaT = 3.59939e21 Time = 1.883575796235934 forces forces: Not including porosity effects Restraint verticalSpring: attachmentPt  anchor (0 9.23421 0) spring length 9.23421 force (0 98.8702 0) 6DoF rigid body motion Centre of rotation: (0.280485 9.24123 0) Centre of mass: (0.280485 9.24123 0) Orientation: (1 0 0 0 1 0 0 0 1) Linear velocity: (0 1.382e+18 0) Angular velocity: (0 0 0) GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.017213, No Iterations 13 GAMG: Solving for pcorr, Initial residual = 0.472833, Final residual = 0.0116254, No Iterations 5 time step continuity errors : sum local = 5.49285e07, global = 1.49488e08, cumulative = 1.04105e05 PIMPLE: iteration 1 smoothSolver: Solving for Ux, Initial residual = 0.0876311, Final residual = 0.000118407, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 0.0125489, Final residual = 1.59195e05, No Iterations 1 GAMG: Solving for p, Initial residual = 0.389902, Final residual = 0.00248264, No Iterations 14 GAMG: Solving for p, Initial residual = 0.553004, Final residual = 0.00445544, No Iterations 7 time step continuity errors : sum local = 3.29021e07, global = 1.29096e08, cumulative = 1.03976e05 GAMG: Solving for p, Initial residual = 0.621976, Final residual = 0.00358929, No Iterations 14 GAMG: Solving for p, Initial residual = 0.446588, Final residual = 0.00358063, No Iterations 7 time step continuity errors : sum local = 2.32644e07, global = 8.9411e09, cumulative = 1.03886e05 PIMPLE: iteration 2 smoothSolver: Solving for Ux, Initial residual = 0.0111158, Final residual = 2.48451e07, No Iterations 2 smoothSolver: Solving for Uy, Initial residual = 0.00147112, Final residual = 2.51958e08, No Iterations 2 GAMG: Solving for p, Initial residual = 0.633415, Final residual = 0.00361362, No Iterations 14 GAMG: Solving for p, Initial residual = 0.465718, Final residual = 0.003714, No Iterations 7 time step continuity errors : sum local = 2.50486e07, global = 9.62316e09, cumulative = 1.0379e05 GAMG: Solving for p, Initial residual = 0.119757, Final residual = 0.00082459, No Iterations 7 GAMG: Solving for p, Initial residual = 0.0346993, Final residual = 7.58565e08, No Iterations 26 time step continuity errors : sum local = 8.35769e12, global = 4.16261e14, cumulative = 1.0379e05 ExecutionTime = 793.06 s ClockTime = 1597 s fieldAverage fieldAverage1 write: Calculating averages forces forces write: sum of forces: pressure : (1.50783e+37 5.49819e+39 1.52322e+19) viscous : (8.90904e+18 2.87163e+19 59.2447) porous : (0 0 0) sum of moments: pressure : (1.36597e+20 6.5933e+18 6.88034e+39) viscous : (548.733 7.40703 1.02861e+20) porous : (0 0 0) forceCoeffs forceCoeffs write: Cm = 1.12332e+40 Cd = 2.46177e+37 Cl = 8.97663e+39 Cl(f) = 1.57215e+40 Cl(r) = 6.74489e+39 Courant Number mean: 0.00837317 max: 1.43518 deltaT = 4.10099e21 Time = 1.883575796235934 forces forces: Not including porosity effects Restraint verticalSpring: attachmentPt  anchor (0 9.24123 0) spring length 9.24123 force (0 98.9453 0) 6DoF rigid body motion Centre of rotation: (0.280485 9.24755 0) Centre of mass: (0.280485 9.24755 0) Orientation: (1 0 0 0 1 0 0 0 1) Linear velocity: (0 1.69837e+18 0) Angular velocity: (0 0 0) GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.01525, No Iterations 14 GAMG: Solving for pcorr, Initial residual = 0.471027, Final residual = 0.0188302, No Iterations 4 time step continuity errors : sum local = 6.06274e07, global = 1.3257e08, cumulative = 1.03657e05 PIMPLE: iteration 1 smoothSolver: Solving for Ux, Initial residual = 0.220999, Final residual = 0.000216505, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 0.0302858, Final residual = 2.76543e05, No Iterations 1 GAMG: Solving for p, Initial residual = 0.150527, Final residual = 0.00112312, No Iterations 14 GAMG: Solving for p, Initial residual = 0.226602, Final residual = 0.00217593, No Iterations 7 time step continuity errors : sum local = 1.41945e07, global = 7.71576e09, cumulative = 1.03735e05 GAMG: Solving for p, Initial residual = 0.128788, Final residual = 0.000958094, No Iterations 14 GAMG: Solving for p, Initial residual = 0.184062, Final residual = 0.00175177, No Iterations 7 time step continuity errors : sum local = 1.00278e07, global = 5.32282e09, cumulative = 1.03788e05 PIMPLE: iteration 2 smoothSolver: Solving for Ux, Initial residual = 0.0986745, Final residual = 2.10818e08, No Iterations 3 smoothSolver: Solving for Uy, Initial residual = 0.021731, Final residual = 1.6546e07, No Iterations 2 GAMG: Solving for p, Initial residual = 0.162085, Final residual = 0.00142636, No Iterations 14 GAMG: Solving for p, Initial residual = 0.341383, Final residual = 0.00320235, No Iterations 7 time step continuity errors : sum local = 2.16111e07, global = 1.16693e08, cumulative = 1.03905e05 GAMG: Solving for p, Initial residual = 0.318819, Final residual = 0.00169682, No Iterations 7 GAMG: Solving for p, Initial residual = 0.0983, Final residual = 9.09694e08, No Iterations 25 time step continuity errors : sum local = 2.31849e12, global = 1.75734e13, cumulative = 1.03905e05 ExecutionTime = 793.68 s ClockTime = 1599 s fieldAverage fieldAverage1 write: Calculating averages forces forces write: sum of forces: pressure : (5.92266e+36 8.01276e+38 3.23412e+18) viscous : (8.85916e+18 1.7958e+19 23.3363) porous : (0 0 0) sum of moments: pressure : (3.04516e+19 8.96344e+17 1.04569e+39) viscous : (219.798 6.38085 9.69291e+19) porous : (0 0 0) forceCoeffs forceCoeffs write: Cm = 1.70725e+39 Cd = 9.66964e+36 Cl = 1.3082e+39 Cl(f) = 2.36136e+39 Cl(r) = 1.05315e+39 Courant Number mean: 0.00692353 max: 1.16656 deltaT = 4.80407e21 Time = 1.883575796235934 forces forces: Not including porosity effects Restraint verticalSpring: attachmentPt  anchor (0 9.24755 0) spring length 9.24755 force (0 99.013 0) 6DoF rigid body motion Centre of rotation: (0.280485 9.25888 0) Centre of mass: (0.280485 9.25888 0) Orientation: (1 0 0 0 1 0 0 0 1) Linear velocity: (0 3.01891e+18 0) Angular velocity: (0 0 0) GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.0194931, No Iterations 13 GAMG: Solving for pcorr, Initial residual = 0.475357, Final residual = 0.0117041, No Iterations 5 time step continuity errors : sum local = 1.28399e06, global = 3.8277e08, cumulative = 1.04287e05 PIMPLE: iteration 1 smoothSolver: Solving for Ux, Initial residual = 0.0622515, Final residual = 0.000173185, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 0.0108993, Final residual = 2.75533e05, No Iterations 1 GAMG: Solving for p, Initial residual = 0.693178, Final residual = 0.00518598, No Iterations 14 GAMG: Solving for p, Initial residual = 0.496134, Final residual = 0.00397948, No Iterations 7 time step continuity errors : sum local = 5.39988e07, global = 1.98085e08, cumulative = 1.04485e05 GAMG: Solving for p, Initial residual = 0.36376, Final residual = 0.00223436, No Iterations 14 GAMG: Solving for p, Initial residual = 0.304788, Final residual = 0.00242902, No Iterations 7 time step continuity errors : sum local = 3.75711e07, global = 1.33077e08, cumulative = 1.04618e05 PIMPLE: iteration 2 smoothSolver: Solving for Ux, Initial residual = 0.0296349, Final residual = 3.19176e07, No Iterations 3 smoothSolver: Solving for Uy, Initial residual = 0.00491257, Final residual = 5.53792e07, No Iterations 2 GAMG: Solving for p, Initial residual = 0.29698, Final residual = 0.00258741, No Iterations 13 GAMG: Solving for p, Initial residual = 0.23883, Final residual = 0.00196561, No Iterations 7 time step continuity errors : sum local = 3.33194e07, global = 1.10358e08, cumulative = 1.04729e05 GAMG: Solving for p, Initial residual = 0.0799564, Final residual = 0.000502528, No Iterations 8 GAMG: Solving for p, Initial residual = 0.0243955, Final residual = 6.41177e08, No Iterations 25 time step continuity errors : sum local = 1.51374e11, global = 4.87715e14, cumulative = 1.04729e05 ExecutionTime = 794.27 s ClockTime = 1600 s fieldAverage fieldAverage1 write: Calculating averages forces forces write: sum of forces: pressure : (2.26653e+37 7.39699e+39 5.44652e+19) viscous : (8.76194e+18 4.3249e+19 130.447) porous : (0 0 0) sum of moments: pressure : (5.08955e+20 2.40672e+19 8.91389e+39) viscous : (1195.8 87.193 1.10644e+20) porous : (0 0 0) forceCoeffs forceCoeffs write: Cm = 1.45533e+40 Cd = 3.70045e+37 Cl = 1.20767e+40 Cl(f) = 2.05916e+40 Cl(r) = 8.51492e+39 Courant Number mean: 0.0170929 max: 2.75666 deltaT = 3.48543e21 Time = 1.883575796235934 forces forces: Not including porosity effects Restraint verticalSpring: attachmentPt  anchor (0 9.25888 0) spring length 9.25888 force (0 99.1343 0) 6DoF rigid body motion Centre of rotation: (0.280485 9.26765 0) Centre of mass: (0.280485 9.26765 0) Orientation: (1 0 0 0 1 0 0 0 1) Linear velocity: (0 2.01578e+18 0) Angular velocity: (0 0 0) GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.0151311, No Iterations 14 GAMG: Solving for pcorr, Initial residual = 0.476142, Final residual = 0.0191458, No Iterations 4 time step continuity errors : sum local = 2.22023e07, global = 4.91909e09, cumulative = 1.0468e05 PIMPLE: iteration 1 smoothSolver: Solving for Ux, Initial residual = 0.140065, Final residual = 0.000267872, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 0.0211073, Final residual = 3.56625e05, No Iterations 1 GAMG: Solving for p, Initial residual = 0.267493, Final residual = 0.002458, No Iterations 14 GAMG: Solving for p, Initial residual = 0.514274, Final residual = 0.00461277, No Iterations 7 time step continuity errors : sum local = 3.23868e07, global = 2.21413e08, cumulative = 1.04458e05 GAMG: Solving for p, Initial residual = 0.318334, Final residual = 0.00275394, No Iterations 14 GAMG: Solving for p, Initial residual = 0.507438, Final residual = 0.00468354, No Iterations 7 time step continuity errors : sum local = 2.35224e07, global = 1.26793e08, cumulative = 1.04331e05 PIMPLE: iteration 2 smoothSolver: Solving for Ux, Initial residual = 0.037576, Final residual = 9.85391e08, No Iterations 3 smoothSolver: Solving for Uy, Initial residual = 0.00479482, Final residual = 1.87923e07, No Iterations 2 GAMG: Solving for p, Initial residual = 0.283688, Final residual = 0.00266262, No Iterations 14 GAMG: Solving for p, Initial residual = 0.550086, Final residual = 0.00506526, No Iterations 7 time step continuity errors : sum local = 3.24593e07, global = 1.73568e08, cumulative = 1.04158e05 GAMG: Solving for p, Initial residual = 0.238318, Final residual = 0.00237296, No Iterations 6 GAMG: Solving for p, Initial residual = 0.0725705, Final residual = 5.86767e08, No Iterations 26 time step continuity errors : sum local = 3.54871e12, global = 2.73579e13, cumulative = 1.04158e05 ExecutionTime = 794.89 s ClockTime = 1601 s fieldAverage fieldAverage1 write: Calculating averages forces forces write: sum of forces: pressure : (2.60458e+37 3.00623e+39 1.41423e+19) viscous : (9.85558e+18 4.19069e+19 13.4112) porous : (0 0 0) sum of moments: pressure : (1.37712e+20 1.01025e+17 3.87417e+39) viscous : (140.312 3.8486 1.19684e+20) porous : (0 0 0) forceCoeffs forceCoeffs write: Cm = 6.32518e+39 Cd = 4.25238e+37 Cl = 4.90814e+39 Cl(f) = 8.77925e+39 Cl(r) = 3.87111e+39 [0] #0 Foam::error::printStack(Foam::Ostream&) at ??:? [0] #1 Foam::sigFpe::sigHandler(int) at ??:? [0] #2 ? in "/lib/x86_64linuxgnu/libc.so.6" [0] #3 void Foam::vtkSurfaceWriter::writeData<double>(Foam::Ostream&, Foam::Field<double> const&) at ??:? [0] #4 void Foam::vtkSurfaceWriter::writeTemplate<double>(Foam::fileName const&, Foam::fileName const&, Foam::Field<Foam::Vector<double> > const&, Foam::List<Foam::face> const&, Foam::word const&, Foam::Field<double> const&, bool, bool) const at ??:? [0] #5 void Foam::sampledSurfaces::writeSurface<double>(Foam::Field<double> const&, int, Foam::word const&, Foam::fileName const&) at ??:? [0] #6 void Foam::sampledSurfaces::sampleAndWrite<double>(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:? [0] #7 void Foam::sampledSurfaces::sampleAndWrite<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> >(Foam::IOobjectList const&) at ??:? [0] #8 Foam::sampledSurfaces::write() at ??:? [0] #9 Foam::functionObjects::timeControl::write() at ??:? [0] #10 Foam::functionObjectList::execute() at ??:? [0] #11 Foam::Time::run() const at Time.C:? [0] #12 ? in "/home/ying/OpenFOAM41/OpenFOAM4.1/platforms/linux64GccDPInt32Opt/bin/pimpleDyMFoam" [0] #13 __libc_start_main in "/lib/x86_64linuxgnu/libc.so.6" [0] #14 ?[ubuntu:62701] *** Process received signal *** Thanks! 

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