[Scabbard]

Dear Foamers,

I just start to learn how to use the SixDoFRigidBodyMotion to solve a self oscillating cylinder case. I let the cylinder can oscillating in transverse side without rotation. However during the simulation, the cylinder keeping moving on one side, even I set 2 spring to restrain it.

Here is the error

Courant Number mean: 0.0109312387968 max: 1.08925409942
Time = 10.3


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.0799209127 0) spring length 1.0799209127 force (-0 0.449064904401 -0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.920079087297 0) spring length 0.920079087297 force (0 0.449064904401 0)
Centre of mass: (0 -0.0799209127033 0.1875)
Linear velocity: (0 -0.0532063906146 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 9.04437162716e-05, Final residual = 2.65680565916e-07, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.000267538785308, Final residual = 1.36657039582e-06, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.000155422991715, Final residual = 3.50471070684e-07, No Iterations 1
DICPCG:  Solving for p, Initial residual = 0.00519447486232, Final residual = 5.14668562099e-05, No Iterations 37
DICPCG:  Solving for p, Initial residual = 0.000828384358588, Final residual = 8.18767989941e-06, No Iterations 80
time step continuity errors : sum local = 4.06532945873e-12, global = -9.22735778686e-14, cumulative = 1.60535882438e-10
DICPCG:  Solving for p, Initial residual = 0.000311192366693, Final residual = 3.10976258001e-06, No Iterations 84
DICPCG:  Solving for p, Initial residual = 5.90847533569e-05, Final residual = 9.91055128904e-07, No Iterations 258
time step continuity errors : sum local = 4.92101045989e-13, global = -1.4595937013e-14, cumulative = 1.60521286501e-10
DILUPBiCG:  Solving for k, Initial residual = 3.65228017521e-05, Final residual = 3.54219785688e-07, No Iterations 1
ExecutionTime = 20639.33 s  ClockTime = 20761 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 0.0106133975758 max: 21.0445882013
Time = 13.696


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.22101441506 0) spring length 1.22101441506 force (-0 1.02646479668 -0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.778985584937 0) spring length 0.778985584937 force (0 1.02646479668 0)
Centre of mass: (0 -0.221014415063 0.1875)
Linear velocity: (0 -0.00171786018482 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 0.000981734792019, Final residual = 5.08165819999e-06, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 0.0197041717416, Final residual = 7.16491372836e-06, No Iterations 3
DILUPBiCG:  Solving for Uz, Initial residual = 0.005202940185, Final residual = 4.18296491457e-06, No Iterations 3
DICPCG:  Solving for p, Initial residual = 0.732227583455, Final residual = 0.00731362161027, No Iterations 23
DICPCG:  Solving for p, Initial residual = 0.0619699691031, Final residual = 0.000604818066356, No Iterations 61
time step continuity errors : sum local = 7.22207466644e-08, global = -1.86004765892e-13, cumulative = 1.81335038201e-10
DICPCG:  Solving for p, Initial residual = 0.320262352751, Final residual = 0.0031161672658, No Iterations 30
DICPCG:  Solving for p, Initial residual = 0.0452874168867, Final residual = 9.81923937282e-07, No Iterations 504
time step continuity errors : sum local = 1.46216565128e-10, global = 4.21289409294e-13, cumulative = 1.81756327611e-10
DILUPBiCG:  Solving for k, Initial residual = 0.542737284326, Final residual = 4.91709917765e-07, No Iterations 6
bounding k, min: -320.225630407 max: 3160.9004272 average: 0.0228930866665
ExecutionTime = 27277.92 s  ClockTime = 27417 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 0.0107215198588 max: 84.1974069195
Time = 13.698


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.22101775679 0) spring length 1.22101775679 force (-0 1.02634097701 -0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.778982243211 0) spring length 0.778982243211 force (0 1.02634097701 0)
Centre of mass: (0 -0.221017756789 0.1875)
Linear velocity: (0 -0.00158230773631 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 0.00673451447727, Final residual = 4.24583889248e-07, No Iterations 5
DILUPBiCG:  Solving for Uy, Initial residual = 0.100125393852, Final residual = 5.78370299627e-07, No Iterations 6
DILUPBiCG:  Solving for Uz, Initial residual = 0.0394256338853, Final residual = 6.85940002997e-06, No Iterations 5
DICPCG:  Solving for p, Initial residual = 0.748736219048, Final residual = 0.00746554410887, No Iterations 30
DICPCG:  Solving for p, Initial residual = 0.0519635582214, Final residual = 0.000513419210323, No Iterations 132
time step continuity errors : sum local = 1.72054986051e-07, global = 8.12991642331e-09, cumulative = 8.31167275093e-09
DICPCG:  Solving for p, Initial residual = 0.247753969483, Final residual = 0.00235112009563, No Iterations 22
DICPCG:  Solving for p, Initial residual = 0.0356436546234, Final residual = 9.92662333369e-07, No Iterations 486
time step continuity errors : sum local = 3.42556826514e-10, global = -5.13481427704e-13, cumulative = 8.3111592695e-09
DILUPBiCG:  Solving for k, Initial residual = 0.577722517719, Final residual = 8.89588409476e-06, No Iterations 8
bounding k, min: -145.00281533 max: 25832.2022178 average: 0.159463524258
ExecutionTime = 27284.38 s  ClockTime = 27423 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 0.0112451548724 max: 128.020077496
Time = 13.7


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.22102074429 0) spring length 1.22102074429 force (-0 1.02609233939 -0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.778979255706 0) spring length 0.778979255706 force (0 1.02609233939 0)
Centre of mass: (0 -0.221020744294 0.1875)
Linear velocity: (0 -0.00163579550348 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 0.0260753175353, Final residual = 9.89829065521e-06, No Iterations 8
DILUPBiCG:  Solving for Uy, Initial residual = 0.250839697688, Final residual = 7.15796413028e-06, No Iterations 10
DILUPBiCG:  Solving for Uz, Initial residual = 0.106251779796, Final residual = 9.15101050695e-06, No Iterations 11
DICPCG:  Solving for p, Initial residual = 0.787515538158, Final residual = 0.00778539070755, No Iterations 39
DICPCG:  Solving for p, Initial residual = 0.0705072051515, Final residual = 0.000694330803838, No Iterations 111
time step continuity errors : sum local = 5.60486267258e-07, global = 6.82022557025e-09, cumulative = 1.51313848397e-08
DICPCG:  Solving for p, Initial residual = 0.426501354857, Final residual = 0.00390156619624, No Iterations 40
DICPCG:  Solving for p, Initial residual = 0.0618570371929, Final residual = 9.91201036366e-07, No Iterations 527
time step continuity errors : sum local = 9.08211203163e-10, global = 2.87831689472e-12, cumulative = 1.51342631566e-08
DILUPBiCG:  Solving for k, Initial residual = 0.583036768961, Final residual = 1.65629079001, No Iterations 1001
bounding k, min: -160992.181824 max: 283946.686233 average: 1.34641967111
ExecutionTime = 27308.97 s  ClockTime = 27448 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 0.0119781088857 max: 347.604475264
Time = 13.702


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.22102429997 0) spring length 1.22102429997 force (-0 1.02652982604 -0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.778975700029 0) spring length 0.778975700029 force (0 1.02652982604 0)
Centre of mass: (0 -0.221024299971 0.1875)
Linear velocity: (0 -0.00284836446883 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 0.0982341712235, Final residual = 4.45903351925e-06, No Iterations 26
DILUPBiCG:  Solving for Uy, Initial residual = 0.409462000123, Final residual = 3.86441059993e-06, No Iterations 21
DILUPBiCG:  Solving for Uz, Initial residual = 0.335905464232, Final residual = 9.14172833687e-06, No Iterations 25
DICPCG:  Solving for p, Initial residual = 0.888020796374, Final residual = 0.00827370568873, No Iterations 49
DICPCG:  Solving for p, Initial residual = 0.0718109060567, Final residual = 0.00067471345493, No Iterations 142
time step continuity errors : sum local = 1.91139587882e-06, global = -1.62091143245e-07, cumulative = -1.46956880089e-07
DICPCG:  Solving for p, Initial residual = 0.525498466427, Final residual = 0.00498104449879, No Iterations 47
DICPCG:  Solving for p, Initial residual = 0.0792089781293, Final residual = 9.95034005181e-07, No Iterations 571
time step continuity errors : sum local = 2.86061368525e-09, global = -3.61199521261e-11, cumulative = -1.46993000041e-07
DILUPBiCG:  Solving for k, Initial residual = 0.818441261845, Final residual = 0.831303805649, No Iterations 1001
bounding k, min: -1374675.08971 max: 2075441.99778 average: 17.086673809
ExecutionTime = 27335.15 s  ClockTime = 27474 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 0.0159705393611 max: 2131.89878069
Time = 13.704


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.22103213775 0) spring length 1.22103213775 force (-0 1.029739174 -0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.778967862248 0) spring length 0.778967862248 force (0 1.029739174 0)
Centre of mass: (0 -0.221032137752 0.1875)
Linear velocity: (0 0.00174067934966 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 0.361380147815, Final residual = 9.7336612789e-06, No Iterations 43
DILUPBiCG:  Solving for Uy, Initial residual = 0.71095276755, Final residual = 4.55302559739e-06, No Iterations 37
DILUPBiCG:  Solving for Uz, Initial residual = 0.505356221838, Final residual = 8.48014310685e-06, No Iterations 39
DICPCG:  Solving for p, Initial residual = 0.937083546566, Final residual = 0.00927643781904, No Iterations 73
DICPCG:  Solving for p, Initial residual = 0.0774371477986, Final residual = 0.000720015011389, No Iterations 140
time step continuity errors : sum local = 1.24288006078e-05, global = -8.62398331206e-07, cumulative = -1.00939133125e-06
DICPCG:  Solving for p, Initial residual = 0.500949169502, Final residual = 0.00470319735647, No Iterations 39
DICPCG:  Solving for p, Initial residual = 0.0660866709647, Final residual = 9.5764418153e-07, No Iterations 527
time step continuity errors : sum local = 1.47065754022e-08, global = -3.38323363926e-11, cumulative = -1.00942516358e-06
DILUPBiCG:  Solving for k, Initial residual = 0.902538467373, Final residual = 0.0189633224455, No Iterations 1001
bounding k, min: -5835637.83141 max: 12943805.3498 average: 291.91211712
ExecutionTime = 27360.46 s  ClockTime = 27499 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 0.0456887140939 max: 8344.68736926
Time = 13.706


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.22101733725 0) spring length 1.22101733725 force (0 1.01289564537 0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.778982662747 0) spring length 0.778982662747 force (0 1.01289564537 0)
Centre of mass: (0 -0.221017337253 0.1875)
Linear velocity: (0 0.0389519586898 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 0.578815755824, Final residual = 9.06929629318e-06, No Iterations 31
DILUPBiCG:  Solving for Uy, Initial residual = 0.661732278364, Final residual = 1.92735011577e-06, No Iterations 39
DILUPBiCG:  Solving for Uz, Initial residual = 0.60627751069, Final residual = 5.03433336641e-06, No Iterations 39
DICPCG:  Solving for p, Initial residual = 0.942145370572, Final residual = 0.00932981596287, No Iterations 142
DICPCG:  Solving for p, Initial residual = 0.145055141634, Final residual = 0.00144934655699, No Iterations 323
time step continuity errors : sum local = 0.000145834682691, global = 1.89661474403e-06, cumulative = 8.87189580444e-07
DICPCG:  Solving for p, Initial residual = 0.448655212254, Final residual = 0.00385821698642, No Iterations 52
DICPCG:  Solving for p, Initial residual = 0.0773656115561, Final residual = 9.81992226334e-07, No Iterations 545
time step continuity errors : sum local = 1.01029619804e-07, global = -4.31866480992e-12, cumulative = 8.87185261779e-07
DILUPBiCG:  Solving for k, Initial residual = 0.722784419631, Final residual = 8604.31406405, No Iterations 1001
bounding k, min: -1.06682692781e+12 max: 702527041717 average: -11285490.945
ExecutionTime = 27387.68 s  ClockTime = 27527 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 0.437784340694 max: 18673.1207543
Time = 13.708


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.22087632992 0) spring length 1.22087632992 force (0 0.918723162238 0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.779123670083 0) spring length 0.779123670083 force (0 0.918723162238 0)
Centre of mass: (0 -0.220876329917 0.1875)
Linear velocity: (0 -1.42921474716 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 0.825010891958, Final residual = 4.25291821493e-06, No Iterations 134
DILUPBiCG:  Solving for Uy, Initial residual = 0.880025015236, Final residual = 8.32614599604e-06, No Iterations 80
DILUPBiCG:  Solving for Uz, Initial residual = 0.759046120698, Final residual = 6.51395506138e-06, No Iterations 111
DICPCG:  Solving for p, Initial residual = 0.84751761744, Final residual = 0.00843329923351, No Iterations 166
DICPCG:  Solving for p, Initial residual = 0.0247560662329, Final residual = 0.000243293447222, No Iterations 327
time step continuity errors : sum local = 0.000878428953653, global = 3.35137197345e-05, cumulative = 3.44009049963e-05
DICPCG:  Solving for p, Initial residual = 0.0443514290475, Final residual = 0.000430525341493, No Iterations 84
DICPCG:  Solving for p, Initial residual = 0.0354620151593, Final residual = 9.78799544816e-07, No Iterations 511
time step continuity errors : sum local = 1.19416306863e-06, global = 3.07981790882e-08, cumulative = 3.44317031754e-05
DILUPBiCG:  Solving for k, Initial residual = 0.995406417042, Final residual = 6.45552929182e-06, No Iterations 31
bounding k, min: -35367714623.7 max: 31143213775.9 average: 672355.609645
ExecutionTime = 27403.17 s  ClockTime = 27542 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 1.55644669094 max: 39992.2311908
Time = 13.71


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.22673419624 0) spring length 1.22673419624 force (-0 5.39102511079 -0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.773265803758 0) spring length 0.773265803758 force (0 5.39102511079 0)
Centre of mass: (0 -0.226734196242 0.1875)
Linear velocity: (0 -16.0199907538 0)
Angular velocity: (0 0 0)
DILUPBiCG:  Solving for Ux, Initial residual = 0.892427485833, Final residual = 8.14219573621e-06, No Iterations 118
DILUPBiCG:  Solving for Uy, Initial residual = 0.920370219391, Final residual = 1.88441933973e-06, No Iterations 110
DILUPBiCG:  Solving for Uz, Initial residual = 0.87089733049, Final residual = 9.5301214064e-06, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.895087839364, Final residual = 0.00775997586915, No Iterations 233
DICPCG:  Solving for p, Initial residual = 0.129722691674, Final residual = 0.00128850330874, No Iterations 193
time step continuity errors : sum local = 0.221081440384, global = 0.0509201671096, cumulative = 0.0509545988128
DICPCG:  Solving for p, Initial residual = 0.171649125421, Final residual = 0.00164633645554, No Iterations 452
DICPCG:  Solving for p, Initial residual = 0.0754234436705, Final residual = 9.40248708645e-07, No Iterations 677
time step continuity errors : sum local = 0.0119021213653, global = 4.23279607414e-06, cumulative = 0.0509588316088
DILUPBiCG:  Solving for k, Initial residual = nan, Final residual = nan, No Iterations 1001
ExecutionTime = 27437.91 s  ClockTime = 27577 s

fieldAverage fieldAverage1 output:
    Calculating averages

Courant Number mean: 36576.9239654 max: 24004482042.8
Time = 13.712


Restraint verticalSpring1:  attachmentPt - anchor (0 -1.28495629293 0) spring length 1.28495629293 force (-0 44.4626336745 -0)
Restraint verticalSpring2:  attachmentPt - anchor (0 0.715043707068 0) spring length 0.715043707068 force (0 44.4626336745 0)
Centre of mass: (0 -0.284956292932 0.1875)
Linear velocity: (-nan -nan -nan)
Angular velocity: (-nan -nan -nan)
DILUPBiCG:  Solving for Ux, Initial residual = nan, Final residual = nan, No Iterations 1001
DILUPBiCG:  Solving for Uy, Initial residual = nan, Final residual = nan, No Iterations 1001
DILUPBiCG:  Solving for Uz, Initial residual = nan, Final residual = nan, No Iterations 1001
DICPCG:  Solving for p, Initial residual = nan, Final residual = nan, No Iterations 1001
DICPCG:  Solving for p, Initial residual = nan, Final residual = nan, No Iterations 1001

For the courant number, is keep stable in the first 13s around 1, then it keep increasing

Here is the dynamicMeshDict

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dynamicFvMesh      dynamicMotionSolverFvMesh;

motionSolverLibs ("libsixDoFRigidBodyMotion.so");

solver            sixDoFRigidBodyMotion;

sixDoFRigidBodyMotionCoeffs
{
    patches         (CYLINDER);
    innerDistance   0.001;
    outerDistance   1.5;

    mass            9.97;
    centreOfMass    (0 0 0.1875);
    momentOfInertia (1 1 0.03);
    g               (0 0 0);
    orientation
    (
        1 0 0
        0 1 0
        0 0 1
    );
    angularMomentum (0 0 0);
    rhoName         rhoInf;
    rhoInf          1000;
    report          on;

    constraints
    {

        noRotate1
        {
            sixDoFRigidBodyMotionConstraint axis;
            axis            (0 0 1);
        }
        noRotate2
        {
            sixDoFRigidBodyMotionConstraint axis;
            axis            (1 0 0);
        }
        noRotate3
        {
            sixDoFRigidBodyMotionConstraint axis;
            axis            (0 1 0);
        }
        yLine
        { 
            sixDoFRigidBodyMotionConstraint line;
            direction          (0 1 0);
        }
    }

    restraints
    {
        verticalSpring1
        {
            sixDoFRigidBodyMotionRestraint linearSpring;

            anchor          (0 1.092 0.1875);
            refAttachmentPt (0 0.092 0.1875);
            stiffness       4.6325;
            damping         1.482;
            restLength      1;
        }
        verticalSpring2
        {
            sixDoFRigidBodyMotionRestraint linearSpring;

            anchor          (0 -1.092 0.1875);
            refAttachmentPt (0 -0.092 0.1875);
            stiffness       4.6325;
            damping         1.482;
            restLength      1;
        }
    }
}


// ************************************************************************* //

My finite cylinder's diameter is 0.184m and height is 0.375m. Here is my case
https://drive.google.com/file/d/0B1v...it?usp=sharing

Could you give me some recommendations to solve this problem? Thank you so much for you help.

Best regards,
Scabbard

[tomf]

Well, once your Courant number is above 1, it is possible that your simulation starts to diverge, so you should make sure it always keeps below 1. I am not sure which solver you use, but if it is pimpleDyMFoam you can probably use a variable time step that fulfills this Courant no. condition all the time using and using

maxCo 1;
runTimeModifiable true;

in your controlDict. You may even want to lower your maxCo a bit.

Regards,
Tom