[pbalz]

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:

Starting time loop

Interface Courant Number mean: 0 max: 0
Courant Number mean: 8.0273e-05 max: 0.0100382
deltaT = 2.39992e-05
Time = 2.39992e-05


Restraint translationDamper:  force (-0 -0 -0)
Restraint rotationDamper:  moment (-0 -0 -0)
6-DoF 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 1.23235e-05)
    Angular velocity: (0 2.32008e-09 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 = 9.49826e-10, global = -3.30579e-11, cumulative = -4.13543e-11
smoothSolver:  Solving for alpha.water, Initial residual = 5.63182e-09, Final residual = 1.19013e-13, No Iterations 1
Phase-1 volume fraction = 0.790864  Min(alpha1) = 0  Max(alpha1) = 1.00001
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.790864  Min(alpha1) = -8.01534e-16  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 = 3.84999e-10, global = -3.62078e-11, cumulative = -7.75621e-11
GAMG:  Solving for p_rgh, Initial residual = 0.0246502, Final residual = 1.58645e-05, No Iterations 5
time step continuity errors : sum local = 3.40771e-11, global = -3.0063e-12, cumulative = -8.05684e-11
GAMG:  Solving for p_rgh, Initial residual = 0.00308546, Final residual = 4.63604e-08, No Iterations 11
time step continuity errors : sum local = 9.57511e-14, global = -7.38217e-15, cumulative = -8.05757e-11
smoothSolver:  Solving for omega, Initial residual = 2.37895e-06, Final residual = 2.26823e-12, No Iterations 1
smoothSolver:  Solving for k, Initial residual = 1, Final residual = 3.01431e-11, 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: 9.63109e-05 max: 0.0328231
deltaT = 2.87988e-05
Time = 5.2798e-05


Restraint translationDamper:  force (-0 -0 -0.211866)
Restraint rotationDamper:  moment (-0 -5.37608e-05 -0)
6-DoF rigid body motion
    Centre of rotation: (0 0 7.09807e-10)
    Centre of mass: (0 0 7.09807e-10)
    Orientation: (1 0 1.33631e-13 0 1 0 -1.33631e-13 0 1)
    Linear velocity: (0 0 -8.34663e-05)
    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 = 2.05229e-12, global = -1.18994e-13, cumulative = -8.06947e-11
smoothSolver:  Solving for alpha.water, Initial residual = 3.72614e-09, Final residual = 1.68466e-13, No Iterations 1
Phase-1 volume fraction = 0.790864  Min(alpha1) = -2.42957e-16  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
Phase-1 volume fraction = 0.790864  Min(alpha1) = -9.02248e-10  Max(alpha1) = 1.00001
GAMG:  Solving for p_rgh, Initial residual = 0.00749169, Final residual = 4.46451e-06, No Iterations 9
time step continuity errors : sum local = 1.29741e-11, global = 8.75379e-13, cumulative = -7.98194e-11
GAMG:  Solving for p_rgh, Initial residual = 0.0401748, Final residual = 1.36224e-05, No Iterations 5
time step continuity errors : sum local = 2.42329e-11, global = 9.33856e-13, cumulative = -7.88855e-11
GAMG:  Solving for p_rgh, Initial residual = 0.00439205, Final residual = 2.06961e-08, No Iterations 10
time step continuity errors : sum local = 3.57504e-14, global = 2.9144e-15, cumulative = -7.88826e-11
smoothSolver:  Solving for omega, Initial residual = 2.85482e-06, Final residual = 3.16525e-12, No Iterations 1
smoothSolver:  Solving for k, Initial residual = 0.0587749, Final residual = 3.24357e-08, 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: 1.17239e-11 max: 0.0258687
Courant Number mean: 0.000115569 max: 0.0277234
deltaT = 3.45578e-05
Time = 8.73558e-05

And finally the last time steps before everything explodes:

Restraint translationDamper:  force (-0 -0 -6.62811e+10)
Restraint rotationDamper:  moment (-0 1.08837e+08 -0)
6-DoF 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 = -3.31254e-05, cumulative = -3.35953e-05
smoothSolver:  Solving for alpha.water, Initial residual = 0.000479791, Final residual = 4.8796e-11, No Iterations 3
Phase-1 volume fraction = 0.790864  Min(alpha1) = -1.29611e-10  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
Phase-1 volume fraction = 0.790864  Min(alpha1) = -1.29447e-10  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 = 6.1879e-06, global = -6.77958e-07, cumulative = -3.42732e-05
GAMG:  Solving for p_rgh, Initial residual = 0.000450071, Final residual = 2.31368e-07, No Iterations 7
time step continuity errors : sum local = 1.55703e-06, global = 6.38958e-07, cumulative = -3.36343e-05
GAMG:  Solving for p_rgh, Initial residual = 0.999972, Final residual = 3.22908e-08, 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 = 9.37478e-08, No Iterations 121
smoothSolver:  Solving for k, Initial residual = 0.00732862, Final residual = 9.28197e-08, 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 = 2.00261e-21
--> 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)
6-DoF 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 = 8.20113e-11, No Iterations 58
Phase-1 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
Phase-1 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 = 3.65482e-37, Final residual = 3.65482e-37, 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 = 4.96727e-08, 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/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
[1] #1  Foam::sigFpe::sigHandler(int) in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
[3] #1  Foam::sigFpe::sigHandler(int) in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
[3] #2   in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
[1] #2   in "/lib/x86_64-linux-gnu/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_64-linux-gnu/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/OpenFOAM-2.3.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/OpenFOAM-2.3.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/OpenFOAM-2.3.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/OpenFOAM-2.3.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/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
[1] #6  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
[3] #6  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
[1] #7  Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
[3] #7  Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so"
[1] #8  Foam::fvMatrix<double>::solve() in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so"
[3] #8  Foam::fvMatrix<double>::solve() in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so"
[3] #9  Foam::incompressible::RASModels::kOmegaSST::correct() in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so"
[1] #9  Foam::incompressible::RASModels::kOmegaSST::correct() in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so"
[3] #10   in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so"
[1] #10  

[1]  in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/bin/interDyMFoam"
[1] #11  __libc_start_main[3]  in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/bin/interDyMFoam"
[3] #11  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
[1] #12   in "/lib/x86_64-linux-gnu/libc.so.6"
[3] #12  

[3]  in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/bin/interDyMFoam"
[balz-VirtualBox:03920] *** Process received signal ***
[balz-VirtualBox:03920] Signal: Floating point exception (8)
[balz-VirtualBox:03920] Signal code:  (-6)
[balz-VirtualBox:03920] Failing at address: 0x3e800000f50
[balz-VirtualBox:03920] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x36150) [0x7f2b5747b150]
[balz-VirtualBox:03920] [ 1] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x35) [0x7f2b5747b0d5]
[balz-VirtualBox:03920] [ 2] /lib/x86_64-linux-gnu/libc.so.6(+0x36150) [0x7f2b5747b150]
[balz-VirtualBox:03920] [ 3] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZN4Foam22symGaussSeidelSmoother6smoothERKNS_4wordERNS_5FieldIdEERKNS_9lduMatrixERKS5_RKNS_10FieldFieldIS4_dEERKNS_8UPtrListIKNS_17lduInterfaceFieldEEEhi+0x43c) [0x7f2b58584bcc]
[balz-VirtualBox:03920] [ 4] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZNK4Foam22symGaussSeidelSmoother6smoothERNS_5FieldIdEERKS2_hi+0x2d) [0x7f2b5858505d]
[balz-VirtualBox:03920] [ 5] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZNK4Foam12smoothSolver5solveERNS_5FieldIdEERKS2_h+0x480) [0x7f2b5857dbd0]
[balz-VirtualBox:03920] [ 6] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so(_ZN4Foam8fvMatrixIdE15solveSegregatedERKNS_10dictionaryE+0x137) [0x7f2b5ad9eff7]
[balz-VirtualBox:03920] [ 7] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam8fvMatrixIdE5solveERKNS_10dictionaryE+0x11c) [0x7f2b5bece1ec]
[balz-VirtualBox:03920] [ 8] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam8fvMatrixIdE5solveEv+0xca) [0x7f2b5bece54a]
[balz-VirtualBox:03920] [ 9] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam14incompressible9RASModels9kOmegaSST7correctEv+0xc5b) [0x7f2b5bf144cb]
[balz-VirtualBox:03920] [10] interDyMFoam() [0x42dbc9]
[balz-VirtualBox:03920] [11] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed) [0x7f2b5746676d]
[balz-VirtualBox:03920] [12] interDyMFoam() [0x437abd]
[balz-VirtualBox:03920] *** End of error message ***
[1]  in "/home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/bin/interDyMFoam"
[balz-VirtualBox:03918] *** Process received signal ***
[balz-VirtualBox:03918] Signal: Floating point exception (8)
[balz-VirtualBox:03918] Signal code:  (-6)
[balz-VirtualBox:03918] Failing at address: 0x3e800000f4e
[balz-VirtualBox:03918] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x36150) [0x7f7632c6c150]
[balz-VirtualBox:03918] [ 1] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x35) [0x7f7632c6c0d5]
[balz-VirtualBox:03918] [ 2] /lib/x86_64-linux-gnu/libc.so.6(+0x36150) [0x7f7632c6c150]
[balz-VirtualBox:03918] [ 3] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZN4Foam22symGaussSeidelSmoother6smoothERKNS_4wordERNS_5FieldIdEERKNS_9lduMatrixERKS5_RKNS_10FieldFieldIS4_dEERKNS_8UPtrListIKNS_17lduInterfaceFieldEEEhi+0x43c) [0x7f7633d75bcc]
[balz-VirtualBox:03918] [ 4] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZNK4Foam22symGaussSeidelSmoother6smoothERNS_5FieldIdEERKS2_hi+0x2d) [0x7f7633d7605d]
[balz-VirtualBox:03918] [ 5] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZNK4Foam12smoothSolver5solveERNS_5FieldIdEERKS2_h+0x480) [0x7f7633d6ebd0]
[balz-VirtualBox:03918] [ 6] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so(_ZN4Foam8fvMatrixIdE15solveSegregatedERKNS_10dictionaryE+0x137) [0x7f763658fff7]
[balz-VirtualBox:03918] [ 7] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam8fvMatrixIdE5solveERKNS_10dictionaryE+0x11c) [0x7f76376bf1ec]
[balz-VirtualBox:03918] [ 8] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam8fvMatrixIdE5solveEv+0xca) [0x7f76376bf54a]
[balz-VirtualBox:03918] [ 9] /home/balz/OpenFOAM/OpenFOAM-2.3.x/platforms/linux64GccDPOpt/lib/libincompressibleRASModels.so(_ZN4Foam14incompressible9RASModels9kOmegaSST7correctEv+0xc5b) [0x7f76377054cb]
[balz-VirtualBox:03918] [10] interDyMFoam() [0x42dbc9]
[balz-VirtualBox:03918] [11] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed) [0x7f7632c5776d]
[balz-VirtualBox:03918] [12] interDyMFoam() [0x437abd]
[balz-VirtualBox:03918] *** End of error message ***
--------------------------------------------------------------------------
mpirun noticed that process rank 3 with PID 3920 on node balz-VirtualBox exited on signal 8 (Floating point exception).

I really don't know how to get this case running. After a few disappointing days of trying I ran out of ideas.
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

[olivierG]

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

[JNSN]

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 non-orthonogality?

Best regards,
Jan

[JNSN]

Hi Pascal,

three more suggestions which may help to get your simulation stable:

1. First run interFoam without body motion, after you get a somehow converged flow field, restart with interDyMFoam
2. decrease the acceleration relaxation
3. Run in pimple mode with e.g. 4 outer corrections. Then you may can decrease the piso correctors to 1

Best regards,
Jan

[pbalz]

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

[JNSN]

Hi Pascal,

good to hear that your simulation is running.

Best regards,
Jan

[13msmemusman]

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.

[amcloughlin801]

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

[stephie]

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 = 3.2282e-06, No Iterations 9
time step continuity errors : sum local = 3.62294e-17, global = -1.16441e-18, cumulative = -8.03449e-06
smoothSolver: Solving for alpha.water, Initial residual = 1.59929e-07, Final residual = 2.88917e-09, No Iterations 1
Phase-1 volume fraction = 0.639257 Min(alpha1) = -9.8232e-10 Max(alpha1) = 1
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.639257 Min(alpha1) = -9.8232e-10 Max(alpha1) = 1.00002
smoothSolver: Solving for Ux, Initial residual = 0.00542538, Final residual = 2.48701e-05, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 0.00301165, Final residual = 2.98343e-05, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 0.00378754, Final residual = 2.14696e-05, No Iterations 1
GAMG: Solving for p_rgh, Initial residual = 0.000403278, Final residual = 6.84333e-07, No Iterations 7
time step continuity errors : sum local = 9.49508e-12, global = -4.89945e-14, cumulative = -8.03449e-06
smoothSolver: Solving for omega, Initial residual = 1.14044e-06, Final residual = 2.14799e-10, No Iterations 1
smoothSolver: Solving for k, Initial residual = 1.23566e-07, Final residual = 1.23566e-07, 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: 1.67321e-06 max: 1.00311
Courant Number mean: 8.14204e-06 max: 1.00311
deltaT = 1.6441e-80
--> 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 1e-4, 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
{
"U|k|epsilon|omega" 0.3;
"(U|k|epsilon|omega)Final" 0.8;
}
}

If anyone has a hint how I can solve it, I would be very grateful!

best regards,
Stephie

[amcloughlin801]

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.

[Fauster]

Dear Foamer,

Sorry for digging up this post but I am facing the same problem. I can't stabilized the 2 DOF in trim and sinkage. I am doing resistance analysis for full scale hull.

I managed to obtain very good result on model scale and full scale with interfoam (LTS option on) but when using interDyMFoam I have oscillating motion and pressure behavior. For avoiding initial strong acceleration I initialize with LTS interfoam.

My settings are
accelerationRelaxation 1.0;
no sphericalAngularDamper or linearDamper.

If I understand I should add sphericalAngularDamper and linearDamper (no idea about the correct coeff value ?!) and also decrease the accelerationRelaxation factor. But there is something I don't understand:
Can someone explain me If this coefficients affect the stabilized position of the hull ? Because I would like to compute the true trim and sinkage.
Thanks a lot for helping me,
F

[cyberpr123]

Hii Foamers,

I am doing six DOF analysis with DTC Hull in waves using interDyMFOAM.
Its getting crashed. I m seeing solution in this thread to increase noutercorrectors, for me its already 3, but still its crashing.
Also, its suggested to increase linear & sphericalangular damping,Can anybody tell how this damping is calculated in first place??

Originally Posted by Fauster

Dear Foamer,

Sorry for digging up this post but I am facing the same problem. I can't stabilized the 2 DOF in trim and sinkage. I am doing resistance analysis for full scale hull.

I managed to obtain very good result on model scale and full scale with interfoam (LTS option on) but when using interDyMFoam I have oscillating motion and pressure behavior. For avoiding initial strong acceleration I initialize with LTS interfoam.

My settings are
accelerationRelaxation 1.0;
no sphericalAngularDamper or linearDamper.

If I understand I should add sphericalAngularDamper and linearDamper (no idea about the correct coeff value ?!) and also decrease the accelerationRelaxation factor. But there is something I don't understand:
Can someone explain me If this coefficients affect the stabilized position of the hull ? Because I would like to compute the true trim and sinkage.
Thanks a lot for helping me,
F