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objects oscillate at high speed causing collapse in Dynamic mesh and overset mesh ca

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Old   May 17, 2020, 23:35
Default objects oscillate at high speed causing collapse in Dynamic mesh and overset mesh ca
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Ian
Join Date: Aug 2018
Posts: 15
Rep Power: 6
insane is on a distinguished road
Hi, everyone
Recently I am doing a two degree of freedom objects floating in waves. Firstly, I used the dynamic grid, but only to find the calculating divergence in 0.2 s, the speed and the force of the objects on the Z direction is increased sharply.
I have encountered this kind of problem before, because of deforming of the mesh is too large, but the current motion of the object can be ignored and the mesh deformation could be neglected.
I changed the case to overset case, but there are similar errors, the speed increase sharply, and the oscillation amplitude of the force is particularly large. The gravity and buoyancy are about 140 initially , even completely submerged is no more than 200, but from the log file it can be seen there are some changes of force lager than thousands on a time step.
Here are some timestep results of the log file both in dynamic and overset cases.
Any advice would be appreciated.

For the dynamic mesh, the force on the z-direction is 252 and 1572 in two timesteps.

Code:
deltaT = 0.00101181857516
Time = 0.220738

PIMPLE: iteration 1
forces forces:
    Not including porosity effects

Rigid-body motion of the floatingObject
    Centre of rotation: (0 0 0.00108368499676)
    Orientation: (1 0 3.3789845961e-07 0 1 0 -3.3789845961e-07 0 1)
    Linear velocity: (0 0 0.0612626535315)
    Angular velocity: (0 3.62258814109e-05 0)
Execution time for mesh.update() = 0.5 s
smoothSolver:  Solving for alpha.water, Initial residual = 8.23816903596e-06, Final residual = 7.16032233336e-10, No Iterations 1
Phase-1 volume fraction = 0.500312200358  Min(alpha.water) = -6.36232220187e-30  Max(alpha.water) = 1.00866542511
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.500312200358  Min(alpha.water) = -6.3458477003e-30  Max(alpha.water) = 1.00866542511
Relaxing time: 0.01 s
GAMG:  Solving for p_rgh, Initial residual = 8.64298692691e-05, Final residual = 9.8169399241e-06, No Iterations 9
GAMG:  Solving for p_rgh, Initial residual = 0.00010348168853, Final residual = 9.24900730207e-06, No Iterations 7
time step continuity errors : sum local = 6.61490084731e-08, global = -7.14845366174e-10, cumulative = 2.01813122868e-07
GAMG:  Solving for p_rgh, Initial residual = 1.16441732373e-05, Final residual = 3.42047154349e-06, No Iterations 1
GAMG:  Solving for p_rgh, Initial residual = 3.4197011599e-06, Final residual = 3.4197011599e-06, No Iterations 0
time step continuity errors : sum local = 2.69615713834e-08, global = -9.20554877097e-10, cumulative = 2.00892567991e-07
ExecutionTime = 51.32 s  ClockTime = 51 s

forces forces1 write:
    Sum of forces
        Total    : (-0.18127711571 -1.88236463748e-23 252.403179473)
        Pressure : (-0.18127697457 -1.88237660153e-23 252.415146697)
        Viscous  : (-1.41140473911e-07 1.19640498385e-28 -0.0119672240877)
    Sum of moments
        Total    : (-1.90023955902e-24 -0.0845601499345 3.06605212083e-26)
        Pressure : (-1.90025359991e-24 -0.0845600163142 3.06618198123e-26)
        Viscous  : (1.40408941158e-29 -1.33620321663e-07 -1.29860396598e-30)


Courant Number mean: 0.00254798035261 max: 0.18775947338
Interface Courant Number mean: 2.3084939728e-05 max: 0.0564074055803
deltaT = 0.00107823137739
Time = 0.221816

PIMPLE: iteration 1
forces forces:
    Not including porosity effects

Rigid-body motion of the floatingObject
    Centre of rotation: (0 0 0.00113322650212)
    Orientation: (1 0 3.68934121974e-07 0 1 0 -3.68934121974e-07 0 1)
    Linear velocity: (0 0 0.0306313617895)
    Angular velocity: (0 -9.37936039134e-05 0)
Execution time for mesh.update() = 0.5 s
smoothSolver:  Solving for alpha.water, Initial residual = 1.12888430008e-05, Final residual = 8.47616724924e-10, No Iterations 1
Phase-1 volume fraction = 0.500310401852  Min(alpha.water) = -6.30568122573e-30  Max(alpha.water) = 1.00798849325
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.500310401852  Min(alpha.water) = -6.28823415663e-30  Max(alpha.water) = 1.00798849325
Relaxing time: 0.01 s
GAMG:  Solving for p_rgh, Initial residual = 0.000826027305677, Final residual = 9.345892666e-06, No Iterations 19
GAMG:  Solving for p_rgh, Initial residual = 7.55055385995e-07, Final residual = 7.55055385995e-07, No Iterations 0
time step continuity errors : sum local = 9.73939319788e-08, global = -8.90956534845e-10, cumulative = 2.00001611456e-07
GAMG:  Solving for p_rgh, Initial residual = 2.61538748518e-06, Final residual = 2.61538748518e-06, No Iterations 0
GAMG:  Solving for p_rgh, Initial residual = 2.61538748518e-06, Final residual = 2.61538748518e-06, No Iterations 0
time step continuity errors : sum local = 3.3735638182e-07, global = -1.86581070005e-09, cumulative = 1.98135800756e-07
ExecutionTime = 52.1 s  ClockTime = 52 s

forces forces1 write:
    Sum of forces
        Total    : (0.000986698924306 2.13856484196e-23 1572.88591645)
        Pressure : (0.000986998775467 2.13856973379e-23 1572.89201928)
        Viscous  : (-2.99851160528e-07 -4.89182974308e-29 -0.00610283104064)
    Sum of moments
        Total    : (2.22842317366e-24 0.0084773625331 8.87541932908e-25)
        Pressure : (2.22842813704e-24 0.00847733423395 8.87542806285e-25)
        Viscous  : (-4.96338833053e-30 2.82991556891e-08 -8.73376717721e-31)
For the overset case, the force on the Z-direction is 146 -636 in several timesteps.
Code:
deltaT = 0.00243433879711
Time = 0.216152

PIMPLE: iteration 1
motion_.dropFlag: 0     
 时间 db().time().value():0.216152429581在算了
forces forces:
    rho: rho
    Not including porosity effects

6-DoF rigid body motion
    Centre of rotation: (0 0 -0.0213300442367)
    Centre of mass: (8.76359257368e-09 0 -0.00093004423675)
    Orientation: (1 0 4.29587871259e-07 0 1 0 -4.29587871259e-07 0 1)
    Linear velocity: (0 0 -0.031497857265)
    Angular velocity: (-0 -1.27419889364e-05 0)
cellVolumeWeight : detected 2 mesh regions

    zone:0 nCells:400000
    zone:1 nCells:17900
Marking patch-cells on zone 0
Marking patch-cells on zone 1

After patch analysis : nCells : 417900
    other  : 412560
    patch  : 4744
    overset: 596

Creating mesh-to-mesh addressing for region0 and region0 regions using cellVolumeWeight
meshToMesh: Using AABBTree method
    Overlap volume: 0.134053289585
cellVolumeWeight : detected 6 mesh regions after overset

Front : fraction:1 size:1160
Overset analysis : nCells : 417900
    calculated   : 411602
    interpolated : 946
    hole         : 5352

Updating StokesII wave model for patch inlet
Updating shallowWaterAbsorption wave model for patch outlet
Execution time for mesh.update() = 5.19 s
Updating StokesII wave model for patch inlet
smoothSolver:  Solving for alpha.water, Initial residual = 6.75648006434e-06, Final residual = 3.47092057926e-11, No Iterations 2
Phase-1 volume fraction = 0.405001375012  Min(alpha.water) = -6.44107925227e-19  Max(alpha.water) = 1.00018322668
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.405001377548  Min(alpha.water) = -1.52464097061e-17  Max(alpha.water) = 1.00018322668
Updating StokesII wave model for patch inlet
smoothSolver:  Solving for alpha.water, Initial residual = 6.75808827335e-06, Final residual = 3.46761931325e-11, No Iterations 2
Phase-1 volume fraction = 0.405008116411  Min(alpha.water) = -4.2632907881e-19  Max(alpha.water) = 1.0001801161
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.405008119026  Min(alpha.water) = -1.47698402771e-17  Max(alpha.water) = 1.0001801161
Updating StokesII wave model for patch inlet
DILUPBiCGStab:  Solving for p_rgh, Initial residual = 7.73918900558e-05, Final residual = 7.70896010266e-07, No Iterations 179
time step continuity errors : sum local = 1.39938130275e-07, global = 6.49571398554e-08, cumulative = 4.25418012787e-06
DILUPBiCGStab:  Solving for p_rgh, Initial residual = 0.000258484674878, Final residual = 8.84289053292e-10, No Iterations 402
time step continuity errors : sum local = 3.55495897207e-12, global = -1.37045513846e-12, cumulative = 4.25417875741e-06
smoothSolver:  Solving for epsilon, Initial residual = 0.00248482816424, Final residual = 6.85528578613e-09, No Iterations 15
smoothSolver:  Solving for k, Initial residual = 0.031742998684, Final residual = 9.07836013528e-09, No Iterations 29
PIMPLE: iteration 2
Updating StokesII wave model for patch inlet
smoothSolver:  Solving for alpha.water, Initial residual = 9.70110690882e-06, Final residual = 3.98515135285e-11, No Iterations 2
Phase-1 volume fraction = 0.405001348864  Min(alpha.water) = -1.03030772084e-18  Max(alpha.water) = 1.00018324609
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.405001351346  Min(alpha.water) = -1.36436906282e-17  Max(alpha.water) = 1.00018324609
Updating StokesII wave model for patch inlet
smoothSolver:  Solving for alpha.water, Initial residual = 6.73423582573e-06, Final residual = 3.1136314758e-11, No Iterations 2
Phase-1 volume fraction = 0.405008063893  Min(alpha.water) = -4.26329047505e-19  Max(alpha.water) = 1.00018015426
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.405008066489  Min(alpha.water) = -1.30693638106e-17  Max(alpha.water) = 1.00018015426
Updating StokesII wave model for patch inlet
DILUPBiCGStab:  Solving for p_rgh, Initial residual = 0.000118616893935, Final residual = 9.3012114721e-07, No Iterations 152
time step continuity errors : sum local = 3.13276633314e-09, global = 2.56566848953e-12, cumulative = 4.25418132308e-06
DILUPBiCGStab:  Solving for p_rgh, Initial residual = 0.00011827675578, Final residual = 9.41783544077e-10, No Iterations 305
time step continuity errors : sum local = 5.45493528694e-13, global = -5.65974338958e-14, cumulative = 4.25418126648e-06
smoothSolver:  Solving for epsilon, Initial residual = 0.000163531317999, Final residual = 7.97099529407e-09, No Iterations 8
smoothSolver:  Solving for k, Initial residual = 0.00062846546524, Final residual = 7.07149761854e-09, No Iterations 21
ExecutionTime = 179.75 s  ClockTime = 185 s

forces forces1 write:
    Sum of forces
        Total    : (-0.000835011808457 -5.45382368796e-24 146.54637577)
        Pressure : (-0.000835029384371 -5.45374863573e-24 146.526422965)
        Viscous  : (1.75759144188e-08 -7.50522339763e-29 0.019952805856)
    Sum of moments
        Total    : (-5.21201731689e-25 0.00027807004677 -4.71054295058e-26)
        Pressure : (-5.21194290964e-25 0.00027789856482 -4.71023222581e-26)
        Viscous  : (-7.44072488661e-30 1.71481949812e-07 -3.10724768134e-30)


Courant Number mean: 0.00312599378064 max: 0.293259735409
Interface Courant Number mean: 2.05386331858e-05 max: 0.114626092226
deltaT = 0.00249028949752
Time = 0.218643

PIMPLE: iteration 1
motion_.dropFlag: 0     
 时间 db().time().value():0.218642711639在算了
forces forces:
    rho: rho
    Not including porosity effects

6-DoF rigid body motion
    Centre of rotation: (0 0 -0.0213682344606)
    Centre of mass: (8.20449051472e-09 0 -0.000968234460565)
    Orientation: (1 0 4.02180907584e-07 0 1 0 -4.02180907584e-07 0 1)
    Linear velocity: (0 0 0.000826544670072)
    Angular velocity: (-0 -9.26907740871e-06 0)
cellVolumeWeight : detected 2 mesh regions

    zone:0 nCells:400000
    zone:1 nCells:17900
Marking patch-cells on zone 0
Marking patch-cells on zone 1

After patch analysis : nCells : 417900
    other  : 412560
    patch  : 4744
    overset: 596

Creating mesh-to-mesh addressing for region0 and region0 regions using cellVolumeWeight
meshToMesh: Using AABBTree method
    Overlap volume: 0.134045212245
cellVolumeWeight : detected 6 mesh regions after overset

Front : fraction:1 size:1162
Overset analysis : nCells : 417900
    calculated   : 411600
    interpolated : 946
    hole         : 5354

Updating StokesII wave model for patch inlet
Updating shallowWaterAbsorption wave model for patch outlet
Execution time for mesh.update() = 5.42 s
Updating StokesII wave model for patch inlet
smoothSolver:  Solving for alpha.water, Initial residual = 6.09338592432e-06, Final residual = 2.40627946583e-11, No Iterations 2
Phase-1 volume fraction = 0.405014125102  Min(alpha.water) = -4.26328384992e-19  Max(alpha.water) = 1.00017701078
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.405014127847  Min(alpha.water) = -1.04461042326e-17  Max(alpha.water) = 1.00017701078
Updating StokesII wave model for patch inlet
smoothSolver:  Solving for alpha.water, Initial residual = 6.09441137905e-06, Final residual = 2.40259634767e-11, No Iterations 2
Phase-1 volume fraction = 0.405020187051  Min(alpha.water) = -4.26327722332e-19  Max(alpha.water) = 1.00017392216
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.405020189807  Min(alpha.water) = -9.5120499276e-18  Max(alpha.water) = 1.00017392216
Updating StokesII wave model for patch inlet
DILUPBiCGStab:  Solving for p_rgh, Initial residual = 0.0574319353605, Final residual = 0.000481714923153, No Iterations 252
time step continuity errors : sum local = 1.52454599301e-07, global = 4.71011922379e-08, cumulative = 4.30128245872e-06
DILUPBiCGStab:  Solving for p_rgh, Initial residual = 1.25353035601e-05, Final residual = 5.41520666851e-10, No Iterations 308
time step continuity errors : sum local = 6.27030222368e-10, global = 2.53603809451e-10, cumulative = 4.30153606253e-06
smoothSolver:  Solving for epsilon, Initial residual = 0.0012437548912, Final residual = 7.78688153486e-09, No Iterations 15
smoothSolver:  Solving for k, Initial residual = 0.0115461348311, Final residual = 6.65057162803e-09, No Iterations 30
PIMPLE: iteration 2
Updating StokesII wave model for patch inlet
smoothSolver:  Solving for alpha.water, Initial residual = 1.02524778268e-05, Final residual = 1.47321270306e-11, No Iterations 2
Phase-1 volume fraction = 0.405011011353  Min(alpha.water) = -4.25540370391e-19  Max(alpha.water) = 1.00017702627
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.405011013529  Min(alpha.water) = -9.64123997826e-18  Max(alpha.water) = 1.00017702627
Updating StokesII wave model for patch inlet
smoothSolver:  Solving for alpha.water, Initial residual = 2.9666532562e-06, Final residual = 4.89153378505e-12, No Iterations 2
Phase-1 volume fraction = 0.405013958567  Min(alpha.water) = -4.24733396239e-19  Max(alpha.water) = 1.0001739526
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.405013960729  Min(alpha.water) = -8.74233411734e-18  Max(alpha.water) = 1.0001739526
Updating StokesII wave model for patch inlet
DILUPBiCGStab:  Solving for p_rgh, Initial residual = 1.52984166079e-05, Final residual = 1.1946067314e-07, No Iterations 165
time step continuity errors : sum local = 5.571216882e-08, global = -2.13063622342e-08, cumulative = 4.2802297003e-06
DILUPBiCGStab:  Solving for p_rgh, Initial residual = 3.63683899449e-06, Final residual = 9.07496366273e-10, No Iterations 265
time step continuity errors : sum local = 3.97777309263e-10, global = -1.12705790442e-11, cumulative = 4.28021842972e-06
smoothSolver:  Solving for epsilon, Initial residual = 0.000332863393295, Final residual = 9.72253472451e-09, No Iterations 8
smoothSolver:  Solving for k, Initial residual = 0.00373997689702, Final residual = 7.30870966919e-09, No Iterations 22
ExecutionTime = 186.5 s  ClockTime = 192 s

forces forces1 write:
    Sum of forces
        Total    : (-0.000928906233233 -1.80429377211e-23 -636.496207569)
        Pressure : (-0.00092895466669 -1.8042996157e-23 -636.505199892)
        Viscous  : (4.84334573672e-08 5.84358832828e-29 0.00899232345785)
    Sum of moments
        Total    : (-1.87852470623e-24 -0.000321059082781 5.79075401727e-25)
        Pressure : (-1.87853074491e-24 -0.000321189856886 5.79065804127e-25)
        Viscous  : (6.03867806002e-30 1.30774104865e-07 9.5975999502e-30)


Courant Number mean: 0.00142003472523 max: 0.161714928462
Interface Courant Number mean: 1.28565593805e-05 max: 0.0762584687927
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