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February 10, 2015, 09:28 
interDyMFoam with VOF + 6DOF instable

#1 
Member
Pascal Balz
Join Date: Feb 2015
Location: Germany
Posts: 36
Rep Power: 3 
Dear Foamers,
I try to calculate the pitch angle and draft of a floating body in water, using a VOF approach with dynamic remeshing. The DTCHull tutorial for the interDyMFoam solver is basically exactly what I need, but of course with another geometry. So, after testing some different parameters, I took the DTCHull tutorial and adapted it to my geometry and boundary conditions (i.e. u=3.7 m/s instead of 1.6 m/s). I have not made any change to the major options regarding discretization or solver setup. By the way: I'm running both OF 2.3.0 and 2.3.x on Ubuntu 12.04. This is where the problem all starts. OF starts to calculate the solution and after a few time steps the pressure forces start to become unstable. Afterwards the linear and angular velocity of my solid also start to oscillate  with a rising amplitude... A few timesteps later the velocity has reached really high values, which leads to a high courant number and therefore to a decreasing delta t. Then alpha becomes unbounded and the solution quits with a floating point exception (obviously because of the decreasing time step size). Here are the first two time steps of my logfile. You can clearly see that the pressure forces are already unstable: Code:
Starting time loop Interface Courant Number mean: 0 max: 0 Courant Number mean: 8.0273e05 max: 0.0100382 deltaT = 2.39992e05 Time = 2.39992e05 Restraint translationDamper: force (0 0 0) Restraint rotationDamper: moment (0 0 0) 6DoF rigid body motion Centre of rotation: (0 0 0) Centre of mass: (0 0 0) Orientation: (1 0 0 0 1 0 0 0 1) Linear velocity: (0 0 1.23235e05) Angular velocity: (0 2.32008e09 0) Execution time for mesh.update() = 1.2 s GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.0828371, No Iterations 4 time step continuity errors : sum local = 9.49826e10, global = 3.30579e11, cumulative = 4.13543e11 smoothSolver: Solving for alpha.water, Initial residual = 5.63182e09, Final residual = 1.19013e13, No Iterations 1 Phase1 volume fraction = 0.790864 Min(alpha1) = 0 Max(alpha1) = 1.00001 MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water Phase1 volume fraction = 0.790864 Min(alpha1) = 8.01534e16 Max(alpha1) = 1.00001 GAMG: Solving for p_rgh, Initial residual = 1, Final residual = 0.000695745, No Iterations 6 time step continuity errors : sum local = 3.84999e10, global = 3.62078e11, cumulative = 7.75621e11 GAMG: Solving for p_rgh, Initial residual = 0.0246502, Final residual = 1.58645e05, No Iterations 5 time step continuity errors : sum local = 3.40771e11, global = 3.0063e12, cumulative = 8.05684e11 GAMG: Solving for p_rgh, Initial residual = 0.00308546, Final residual = 4.63604e08, No Iterations 11 time step continuity errors : sum local = 9.57511e14, global = 7.38217e15, cumulative = 8.05757e11 smoothSolver: Solving for omega, Initial residual = 2.37895e06, Final residual = 2.26823e12, No Iterations 1 smoothSolver: Solving for k, Initial residual = 1, Final residual = 3.01431e11, No Iterations 2 ExecutionTime = 35.37 s ClockTime = 36 s forces forces output: sum of forces: pressure : (2.45527e+07 958.752 128685) viscous : (49.4466 0.000300508 0.00483469) porous : (0 0 0) sum of moments: pressure : (226245 2.52705e+08 4.63274e+07) viscous : (0.00899411 17.5397 104.706) porous : (0 0 0) Interface Courant Number mean: 0 max: 0 Courant Number mean: 9.63109e05 max: 0.0328231 deltaT = 2.87988e05 Time = 5.2798e05 Restraint translationDamper: force (0 0 0.211866) Restraint rotationDamper: moment (0 5.37608e05 0) 6DoF rigid body motion Centre of rotation: (0 0 7.09807e10) Centre of mass: (0 0 7.09807e10) Orientation: (1 0 1.33631e13 0 1 0 1.33631e13 0 1) Linear velocity: (0 0 8.34663e05) Angular velocity: (0 0.0432865 0) Execution time for mesh.update() = 1.39 s GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.0872902, No Iterations 2 time step continuity errors : sum local = 2.05229e12, global = 1.18994e13, cumulative = 8.06947e11 smoothSolver: Solving for alpha.water, Initial residual = 3.72614e09, Final residual = 1.68466e13, No Iterations 1 Phase1 volume fraction = 0.790864 Min(alpha1) = 2.42957e16 Max(alpha1) = 1.00001 Applying the previous iteration compression flux MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water Phase1 volume fraction = 0.790864 Min(alpha1) = 9.02248e10 Max(alpha1) = 1.00001 GAMG: Solving for p_rgh, Initial residual = 0.00749169, Final residual = 4.46451e06, No Iterations 9 time step continuity errors : sum local = 1.29741e11, global = 8.75379e13, cumulative = 7.98194e11 GAMG: Solving for p_rgh, Initial residual = 0.0401748, Final residual = 1.36224e05, No Iterations 5 time step continuity errors : sum local = 2.42329e11, global = 9.33856e13, cumulative = 7.88855e11 GAMG: Solving for p_rgh, Initial residual = 0.00439205, Final residual = 2.06961e08, No Iterations 10 time step continuity errors : sum local = 3.57504e14, global = 2.9144e15, cumulative = 7.88826e11 smoothSolver: Solving for omega, Initial residual = 2.85482e06, Final residual = 3.16525e12, No Iterations 1 smoothSolver: Solving for k, Initial residual = 0.0587749, Final residual = 3.24357e08, No Iterations 1 ExecutionTime = 57.99 s ClockTime = 59 s forces forces output: sum of forces: pressure : (1.27512e+06 1470.39 126192) viscous : (49.1517 0.000384695 0.0032971) porous : (0 0 0) sum of moments: pressure : (241862 8.11241e+06 2.46272e+06) viscous : (0.00708633 18.9842 104.16) porous : (0 0 0) Interface Courant Number mean: 1.17239e11 max: 0.0258687 Courant Number mean: 0.000115569 max: 0.0277234 deltaT = 3.45578e05 Time = 8.73558e05 Code:
Restraint translationDamper: force (0 0 6.62811e+10) Restraint rotationDamper: moment (0 1.08837e+08 0) 6DoF rigid body motion Centre of rotation: (0 0 0.153159) Centre of mass: (0 0 0.153159) Orientation: (0.999959 0 0.00901383 0 1 0 0.00901383 0 0.999959) Linear velocity: (0 0 2.27725e+07) Angular velocity: (0 2.02891e+06 0) Execution time for mesh.update() = 1.35 s GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.0625312, No Iterations 4 time step continuity errors : sum local = 0.000358987, global = 3.31254e05, cumulative = 3.35953e05 smoothSolver: Solving for alpha.water, Initial residual = 0.000479791, Final residual = 4.8796e11, No Iterations 3 Phase1 volume fraction = 0.790864 Min(alpha1) = 1.29611e10 Max(alpha1) = 1.04721 Applying the previous iteration compression flux MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water Phase1 volume fraction = 0.790864 Min(alpha1) = 1.29447e10 Max(alpha1) = 1.04721 GAMG: Solving for p_rgh, Initial residual = 0.801051, Final residual = 0.000572986, No Iterations 9 time step continuity errors : sum local = 6.1879e06, global = 6.77958e07, cumulative = 3.42732e05 GAMG: Solving for p_rgh, Initial residual = 0.000450071, Final residual = 2.31368e07, No Iterations 7 time step continuity errors : sum local = 1.55703e06, global = 6.38958e07, cumulative = 3.36343e05 GAMG: Solving for p_rgh, Initial residual = 0.999972, Final residual = 3.22908e08, No Iterations 20 time step continuity errors : sum local = 0.00749391, global = 0.000607174, cumulative = 0.000640809 smoothSolver: Solving for omega, Initial residual = 1, Final residual = 9.37478e08, No Iterations 121 smoothSolver: Solving for k, Initial residual = 0.00732862, Final residual = 9.28197e08, No Iterations 140 ExecutionTime = 2566.2 s ClockTime = 2594 s forces forces output: sum of forces: pressure : (1.37784e+34 2.66482e+34 1.18088e+36) viscous : (1.90643e+18 1.43781e+19 2.28481e+19) porous : (0 0 0) sum of moments: pressure : (2.14866e+36 2.87143e+35 1.80333e+34) viscous : (7.09308e+19 1.06297e+19 6.54609e+18) porous : (0 0 0) Interface Courant Number mean: 113849 max: 3.45359e+08 Courant Number mean: 1.26635e+07 max: 6.24547e+08 deltaT = 2.00261e21 > FOAM Warning : From function Time::operator++() in file db/Time/Time.C at line 1055 Increased the timePrecision from 10 to 11 to distinguish between timeNames at time 0.0823347 Time = 0.082334668882 Restraint translationDamper: force (0 0 4.57787e+11) Restraint rotationDamper: moment (0 4.6905e+10 0) 6DoF rigid body motion Centre of rotation: (0 0 0.153159) Centre of mass: (0 0 0.153159) Orientation: (0.999959 0 0.00901383 0 1 0 0.00901383 0 0.999959) Linear velocity: (0 0 4.84996e+10) Angular velocity: (0 3.44134e+09 0) Execution time for mesh.update() = 1.35 s GAMG: Solving for pcorr, Initial residual = 1, Final residual = 0.0574656, No Iterations 4 time step continuity errors : sum local = 2.40604e+13, global = 1.49371e+12, cumulative = 1.49371e+12 smoothSolver: Solving for alpha.water, Initial residual = 0.391807, Final residual = 8.20113e11, No Iterations 58 Phase1 volume fraction = 0.848726 Min(alpha1) = 0 Max(alpha1) = 6.78522 Applying the previous iteration compression flux MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water MULES: Correcting alpha.water Phase1 volume fraction = 2.79008e+76 Min(alpha1) = 1.87585e+97 Max(alpha1) = 2.50798e+97 GAMG: Solving for p_rgh, Initial residual = 1, Final residual = 0.00714166, No Iterations 1000 time step continuity errors : sum local = 5.71911e+32, global = 1.41715e+31, cumulative = 1.41715e+31 GAMG: Solving for p_rgh, Initial residual = 3.65482e37, Final residual = 3.65482e37, No Iterations 0 time step continuity errors : sum local = 1.2657e+55, global = 5.14288e+54, cumulative = 5.14288e+54 GAMG: Solving for p_rgh, Initial residual = 1, Final residual = 4.96727e08, No Iterations 246 time step continuity errors : sum local = 4.77892e+102, global = 3.54492e+102, cumulative = 3.54492e+102 [1] #0 [3] Foam::error::printStack(Foam::Ostream&)#0 Foam::error::printStack(Foam::Ostream&) in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [1] #1 Foam::sigFpe::sigHandler(int) in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [3] #1 Foam::sigFpe::sigHandler(int) in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [3] #2 in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [1] #2 in "/lib/x86_64linuxgnu/libc.so.6" [3] #3 Foam::symGaussSeidelSmoother::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 "/lib/x86_64linuxgnu/libc.so.6" [1] #3 Foam::symGaussSeidelSmoother::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 "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [3] #4 Foam::symGaussSeidelSmoother::smooth(Foam::Field<double>&, Foam::Field<double> const&, unsigned char, int) const in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [1] #4 Foam::symGaussSeidelSmoother::smooth(Foam::Field<double>&, Foam::Field<double> const&, unsigned char, int) const in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [1] #5 Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [3] #5 Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [1] #6 Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [3] #6 Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so" [1] #7 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so" [3] #7 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so" [1] #8 Foam::fvMatrix<double>::solve() in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so" [3] #8 Foam::fvMatrix<double>::solve() in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so" [3] #9 Foam::incompressible::RASModels::kOmegaSST::correct() in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so" [1] #9 Foam::incompressible::RASModels::kOmegaSST::correct() in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so" [3] #10 in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so" [1] #10 [1] in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/bin/interDyMFoam" [1] #11 __libc_start_main[3] in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/bin/interDyMFoam" [3] #11 __libc_start_main in "/lib/x86_64linuxgnu/libc.so.6" [1] #12 in "/lib/x86_64linuxgnu/libc.so.6" [3] #12 [3] in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/bin/interDyMFoam" [balzVirtualBox:03920] *** Process received signal *** [balzVirtualBox:03920] Signal: Floating point exception (8) [balzVirtualBox:03920] Signal code: (6) [balzVirtualBox:03920] Failing at address: 0x3e800000f50 [balzVirtualBox:03920] [ 0] /lib/x86_64linuxgnu/libc.so.6(+0x36150) [0x7f2b5747b150] [balzVirtualBox:03920] [ 1] /lib/x86_64linuxgnu/libc.so.6(gsignal+0x35) [0x7f2b5747b0d5] [balzVirtualBox:03920] [ 2] /lib/x86_64linuxgnu/libc.so.6(+0x36150) [0x7f2b5747b150] [balzVirtualBox:03920] [ 3] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZN4Foam22symGaussSeidelSmoother6smoothERKNS_4wordERNS_5FieldIdEERKNS_9lduMatrixERKS5_RKNS_10FieldFieldIS4_dEERKNS_8UPtrListIKNS_17lduInterfaceFieldEEEhi+0x43c) [0x7f2b58584bcc] [balzVirtualBox:03920] [ 4] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZNK4Foam22symGaussSeidelSmoother6smoothERNS_5FieldIdEERKS2_hi+0x2d) [0x7f2b5858505d] [balzVirtualBox:03920] [ 5] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZNK4Foam12smoothSolver5solveERNS_5FieldIdEERKS2_h+0x480) [0x7f2b5857dbd0] [balzVirtualBox:03920] [ 6] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so(_ZN4Foam8fvMatrixIdE15solveSegregatedERKNS_10dictionaryE+0x137) [0x7f2b5ad9eff7] [balzVirtualBox:03920] [ 7] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam8fvMatrixIdE5solveERKNS_10dictionaryE+0x11c) [0x7f2b5bece1ec] [balzVirtualBox:03920] [ 8] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam8fvMatrixIdE5solveEv+0xca) [0x7f2b5bece54a] [balzVirtualBox:03920] [ 9] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam14incompressible9RASModels9kOmegaSST7correctEv+0xc5b) [0x7f2b5bf144cb] [balzVirtualBox:03920] [10] interDyMFoam() [0x42dbc9] [balzVirtualBox:03920] [11] /lib/x86_64linuxgnu/libc.so.6(__libc_start_main+0xed) [0x7f2b5746676d] [balzVirtualBox:03920] [12] interDyMFoam() [0x437abd] [balzVirtualBox:03920] *** End of error message *** [1] in "/home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/bin/interDyMFoam" [balzVirtualBox:03918] *** Process received signal *** [balzVirtualBox:03918] Signal: Floating point exception (8) [balzVirtualBox:03918] Signal code: (6) [balzVirtualBox:03918] Failing at address: 0x3e800000f4e [balzVirtualBox:03918] [ 0] /lib/x86_64linuxgnu/libc.so.6(+0x36150) [0x7f7632c6c150] [balzVirtualBox:03918] [ 1] /lib/x86_64linuxgnu/libc.so.6(gsignal+0x35) [0x7f7632c6c0d5] [balzVirtualBox:03918] [ 2] /lib/x86_64linuxgnu/libc.so.6(+0x36150) [0x7f7632c6c150] [balzVirtualBox:03918] [ 3] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZN4Foam22symGaussSeidelSmoother6smoothERKNS_4wordERNS_5FieldIdEERKNS_9lduMatrixERKS5_RKNS_10FieldFieldIS4_dEERKNS_8UPtrListIKNS_17lduInterfaceFieldEEEhi+0x43c) [0x7f7633d75bcc] [balzVirtualBox:03918] [ 4] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZNK4Foam22symGaussSeidelSmoother6smoothERNS_5FieldIdEERKS2_hi+0x2d) [0x7f7633d7605d] [balzVirtualBox:03918] [ 5] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZNK4Foam12smoothSolver5solveERNS_5FieldIdEERKS2_h+0x480) [0x7f7633d6ebd0] [balzVirtualBox:03918] [ 6] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so(_ZN4Foam8fvMatrixIdE15solveSegregatedERKNS_10dictionaryE+0x137) [0x7f763658fff7] [balzVirtualBox:03918] [ 7] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam8fvMatrixIdE5solveERKNS_10dictionaryE+0x11c) [0x7f76376bf1ec] [balzVirtualBox:03918] [ 8] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam8fvMatrixIdE5solveEv+0xca) [0x7f76376bf54a] [balzVirtualBox:03918] [ 9] /home/balz/OpenFOAM/OpenFOAM2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam14incompressible9RASModels9kOmegaSST7correctEv+0xc5b) [0x7f76377054cb] [balzVirtualBox:03918] [10] interDyMFoam() [0x42dbc9] [balzVirtualBox:03918] [11] /lib/x86_64linuxgnu/libc.so.6(__libc_start_main+0xed) [0x7f7632c5776d] [balzVirtualBox:03918] [12] interDyMFoam() [0x437abd] [balzVirtualBox:03918] *** End of error message ***  mpirun noticed that process rank 3 with PID 3920 on node balzVirtualBox exited on signal 8 (Floating point exception). Things I have tried, but without any success: 1. setting the time stepping to fixed and decrease the time step size 2. playing around with the boundary conditions (mainly pressure and velocity) 3. changing the mesh size, varying from 500k cells to 3 mio cells 4. changed some SixDofRigidBodyMotionCoeffs; inner+outer Distance, damping factors, more constraints 5. serial processing 6. increasing the volume of my flow region I really want to know how to get a stable solution without any fluctuations, since this worked perfectly with the dtchull geometry. First I thought it could be some ill conditioned boundary conditions... But at the moment it's more likely that it has something to do with the geometry, because I couldn't achieve a solution with Fluent either. For those who are interested or have an idea on how to solve this problem, please find attached my case directory, including a (simplified) stl. Please, I really need some help on this topic! Any idea on how to reach a solution is highly appreciated! Regards, Pascal 

February 10, 2015, 12:36 

#2 
Senior Member
Olivier
Join Date: Jun 2009
Location: France, grenoble
Posts: 263
Rep Power: 10 
hello,
I didn't look into your case, but if CAL are ok, then try to use more nOuterCorrectors iterations (actually only 1!). regards, olivier 

February 11, 2015, 06:07 

#3 
Member
Jan
Join Date: Jul 2009
Location: Hamburg
Posts: 55
Rep Power: 12 
Hi Pascal,
I had a short look at your setup and at first sight it looks quite reasonable. The oscillating pressure forces at the beginning are normal. This is due to the "wrong" initialisation. At the beginning you have a homogenous velocity and pressure field, and the solver needs some time to stabilize. If you are sure, that your body properties are correct (i.e. mass and moments of inertia, I did not check them), but you do not get a stable solution (oscillating pitch motion), I suggest to increase the rotational damping, e.g. as a first guess by one order of magnitude, to see if it helps. Another point: What is the mesh quality when you use your "real" geometry, especially maximum nonorthonogality? Best regards, Jan 

February 11, 2015, 06:14 

#4 
Member
Jan
Join Date: Jul 2009
Location: Hamburg
Posts: 55
Rep Power: 12 
Hi Pascal,
three more suggestions which may help to get your simulation stable:
Jan 

February 14, 2015, 11:42 

#5 
Member
Pascal Balz
Join Date: Feb 2015
Location: Germany
Posts: 36
Rep Power: 3 
Hi Olivier and Jan,
sorry for answering so late. I have been really busy for the last few days... Anyways, thank you very much for the kind advices! I just started to test them and up until now it very much looks like the solution is stable. For your interest: I increased both the rotational and translational damping; furthermore I switched to 4 outerCorrectors for the PIMPLE solver. Seems like this was the main problem. Now the pressure forces and body velocities are stable and yield reasonable values. Thanks again! Kind regards, Pascal 

February 16, 2015, 04:08 

#6 
Member
Jan
Join Date: Jul 2009
Location: Hamburg
Posts: 55
Rep Power: 12 
Hi Pascal,
good to hear that your simulation is running. Best regards, Jan 

June 20, 2015, 15:53 

#7 
Member
Muhammad Usman
Join Date: Feb 2014
Posts: 91
Rep Power: 4 
I need to find out values of rollA (Roll angle of tank) at every time step in interDyMFoam. i want to write then in a file but first thing is how to bring them in solver. please help. RollA is solved in SDA.C and SDA.H is included in InterDyMFoam.


January 18, 2016, 22:42 
DTCHull tutorial exploding

#8 
New Member
Aidan
Join Date: Jul 2014
Location: Belfast
Posts: 16
Rep Power: 4 
Hi there
I'm having trouble getting the DTCHull tutorial to converge. I am in the process of trying some of the possible solutions mentioned on this thread  namely increasing nOuterCorrectors and increasing translational and rotational damping. Regarding the damping, I have assumed that the relationship between the dampingCoeffs and the magnitude of the damping force is linear  i.e. I have increased the coeficients. Is this correct? Does anyone have a completed, converged log.interDyMFoam file that they could upload, just so I can see what I'm aiming for? Many thanks in advance 

April 25, 2016, 03:47 

#9 
Member
Stephanie
Join Date: Feb 2015
Location: Magdeburg, Germany
Posts: 71
Rep Power: 3 
Hello everyone,
since Friday I have the same problem. At time 106 I have the problem, that the timesteps increase and I don't know why. Selected 2 cells for refinement out of 2167114. Refined from 2167114 to 2167128 cells. Selected 8 split points out of a possible 155456. Unrefined from 2167128 to 2167072 cells. Execution time for mesh.update() = 3 s GAMGPCG: Solving for pcorr, Initial residual = 1, Final residual = 3.2282e06, No Iterations 9 time step continuity errors : sum local = 3.62294e17, global = 1.16441e18, cumulative = 8.03449e06 smoothSolver: Solving for alpha.water, Initial residual = 1.59929e07, Final residual = 2.88917e09, No Iterations 1 Phase1 volume fraction = 0.639257 Min(alpha1) = 9.8232e10 Max(alpha1) = 1 MULES: Correcting alpha.water MULES: Correcting alpha.water Phase1 volume fraction = 0.639257 Min(alpha1) = 9.8232e10 Max(alpha1) = 1.00002 smoothSolver: Solving for Ux, Initial residual = 0.00542538, Final residual = 2.48701e05, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 0.00301165, Final residual = 2.98343e05, No Iterations 1 smoothSolver: Solving for Uz, Initial residual = 0.00378754, Final residual = 2.14696e05, No Iterations 1 GAMG: Solving for p_rgh, Initial residual = 0.000403278, Final residual = 6.84333e07, No Iterations 7 time step continuity errors : sum local = 9.49508e12, global = 4.89945e14, cumulative = 8.03449e06 smoothSolver: Solving for omega, Initial residual = 1.14044e06, Final residual = 2.14799e10, No Iterations 1 smoothSolver: Solving for k, Initial residual = 1.23566e07, Final residual = 1.23566e07, No Iterations 0 ExecutionTime = 66240.1 s ClockTime = 66464 s faceSource inletFlux output: sum(inlet_water_meters) for rhoPhi = 849.745 faceSource outletFlux output: sum(outlet_meters) for rhoPhi = 849.743 faceSource atmosphereFlux output: sum(top_meters) for rhoPhi = 1.57074e+69 Interface Courant Number mean: 1.67321e06 max: 1.00311 Courant Number mean: 8.14204e06 max: 1.00311 deltaT = 1.6441e80 > FOAM Warning : From function Time:perator++() in file db/Time/Time.C at line 1055 Increased the timePrecision from 3999 to 4000 to distinguish between timeNames at time 106.165 Time = 106.1649839677378821534148300997912883758544921875 I use interDyMFoam with an Co of 0.99 and and adaptive timestep. I tried to fix the timestep to 1e4, I set the time back to 102 and I started at 106 the simulation again, but nothing helped my to fix this problem. adjustTimeStep yes; maxCo 0.99; maxAlphaCo 0.99; maxDeltaT 1; Is use the piso mode because pimple wasn't so fast and stable. PIMPLE { } relaxationFactors { fields { p 0.3; pFinal 0.8; } equations { "Ukepsilonomega" 0.3; "(Ukepsilonomega)Final" 0.8; } } If anyone has a hint how I can solve it, I would be very grateful! best regards, Stephie 

May 15, 2016, 23:36 

#10 
New Member
Aidan
Join Date: Jul 2014
Location: Belfast
Posts: 16
Rep Power: 4 
Hi Stephie,
Have you visualised the case right before it crashes to see if you can spot the error? It may just be a mesh problem. 

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