[lil_star]

Hello all,

I have been using openfoam interDyMFoam and DTChull from the past 6 months for my projects but I get incorrect trim angles for every big case. I dont know what I am doing wrong.

Currently I am solving a Full Scale ship with 6Dof to find Heave & Trim Angles, velocity = 0.5m/s. I have used DTChull tutorial as reference and didnt change fvSolution and fvSchemes except for adding relaxation factor of 0.6 in fvSolution. My bc's in 0 directory are same as DTChull.

I will add the case files and images here.

dynamicDict:

dynamicFvMesh       dynamicMotionSolverFvMesh;

motionSolverLibs    ("libsixDoFRigidBodyMotion.so");

solver              sixDoFRigidBodyMotion;

sixDoFRigidBodyMotionCoeffs
{
    patches         (hull);
    innerDistance   5;
    outerDistance   25;

    centreOfMass    (-51.69 0.03 9.15);
    mass            8.8e6;
    momentOfInertia (454446720 9539880000 9628422720);
    rhoInf          1;
    report          on;

    value           uniform (0 0 0);

    accelerationRelaxation 0.4;

    solver
    {
        type Newmark;
    }

    constraints
    {
        zAxis
        {
            sixDoFRigidBodyMotionConstraint line;
            direction     (0 0 1);
        }
        yPlane
        {
            sixDoFRigidBodyMotionConstraint axis;
            axis          (1 1 0);
        }
    }

    restraints
    {
        translationDamper
        {sixDoFRigidBodyMotionRestraint linearDamper;
            coeff         8e7;
        }
        rotationDamper
        {
            sixDoFRigidBodyMotionRestraint sphericalAngularDamper;
            coeff        1.1e8;
        }
    }
}

0/U

Umean 0.5;
mUmean 0.5;

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform ($mUmean 0 0);

boundaryField
{
    //- Set patchGroups for constraint patches
    #includeEtc "caseDicts/setConstraintTypes"

    inlet
    {
        type            fixedValue;
        value           $internalField;
    }

    outlet
    {
        type            outletPhaseMeanVelocity;
        alpha           alpha.water;
        Umean           $Umean;
        value           $internalField;
    }

    atmosphere
    {
        type            pressureInletOutletVelocity;
        tangentialVelocity $internalField;
        value           uniform (0 0 0); }

    hull
    {
        type            movingWallVelocity;
        value           uniform (0 0 0);
    }
}

controlDict

application     interDyMFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         300;

deltaT          0.00001;

writeControl    adjustableRunTime;

writeInterval   5;

purgeWrite      0;

writeFormat     binary;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;

adjustTimeStep  yes;
maxCo           25;
maxAlphaCo      15;
maxDeltaT       0.01;

functions
{
    forces
    {
        type forces;
        functionObjectLibs ( "libforces.so" );
        patches (hull);
        rhoInf  998.8;
        rhoName rho;
        UName   U;
        log     on;
        outputControl   timeStep;
        outputInterval  1;
        CofR (-51.69 0.03 9.15);
    }
}

Log file Just before the case explodes,die,dead!!!

Courant Number mean: 0.0256351 max: 5.78401
Interface Courant Number mean: 0.00253363 max: 5.53433
deltaT = 0.0497512
Time = 84.6766

PIMPLE: iteration 1

Restraint translationDamper:  force (-0 -0 -967445)
Restraint rotationDamper:  moment (-3.06243e+07 -1.37867e+06 51303.4)
6-DoF rigid body motion
    Centre of rotation: (-51.69 0.03 9.18425)
    Centre of mass: (-51.69 0.03 9.18425)
    Orientation: (0.99852 0.0335891 0.0427832 0.0285011 0.346838 -0.937492 -0.0463284 0.937324 0.345367)    Linear velocity: (0 0 0.00336214)
    Angular velocity: (0.19431 0.00874742 -0.00032592)
Execution time for mesh.update() = 1.07 s
GAMG:  Solving for pcorr, Initial residual = 1, Final residual = 0.0840024, No Iterations 2
time step continuity errors : sum local = 8.61761e-07, global = 6.01413e-08, cumulative = -1.84507e-06
smoothSolver:  Solving for alpha.water, Initial residual = 0.000193639, Final residual = 4.12486e-11, No Iterations 9
Phase-1 volume fraction = 0.602648  Min(alpha.water) = -2.38346e-09  Max(alpha.water) = 1.00083
Applying the previous iteration compression flux
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.602648  Min(alpha.water) = -0.000167948  Max(alpha.water) = 1.00083
GAMG:  Solving for p_rgh, Initial residual = 0.0376896, Final residual = 4.55908e-08, No Iterations 12
time step continuity errors : sum local = 7.48747e-10, global = 3.49886e-11, cumulative = -1.84504e-06
PIMPLE: iteration 2

Restraint translationDamper:  force (-0 -0 -403456)
Restraint rotationDamper:  moment (-2.91465e+07 -1.31211e+06 48887.9)
6-DoF rigid body motion
    Centre of rotation: (-51.69 0.03 9.18427)
    Centre of mass: (-51.69 0.03 9.18427)
    Orientation: (0.99852 0.0335896 0.0427834 0.0285016 0.346828 -0.937496 -0.0463285 0.937327 0.345357)    Linear velocity: (0 0 0.00416406)Angular velocity: (0.194749 0.00876719 -0.000326657)
Execution time for mesh.update() = 1.08 s
GAMG:  Solving for pcorr, Initial residual = 1, Final residual = 0.060591, No Iterations 2
time step continuity errors : sum local = 1.79432e-08, global = 6.06704e-09, cumulative = -1.83897e-06
smoothSolver:  Solving for alpha.water, Initial residual = 0.000181902, Final residual = 2.8489e-11, No
Iterations 9
Phase-1 volume fraction = 0.602648  Min(alpha.water) = -2.35388e-09  Max(alpha.water) = 1.00022
Applying the previous iteration compression flux
MULES: Correcting alpha.water
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.602648  Min(alpha.water) = -0.000175539  Max(alpha.water) = 1.00022
GAMG:  Solving for p_rgh, Initial residual = 0.019836, Final residual = 3.1413e-08, No Iterations 12
time step continuity errors : sum local = 5.29268e-10, global = -2.27007e-11, cumulative = -1.83899e-06
smoothSolver:  Solving for omega, Initial residual = 0.000870513, Final residual = 2.88038e-08, No Iterations 5smoothSolver:  Solving for k, Initial residual = 0.0017102, Final residual = 9.83062e-08, No Iterations
5
bounding k, min: -0.0475269 max: 521.21 average: 9.51284
ExecutionTime = 12288.3 s  ClockTime = 12949 s

forces forces output:
    sum of forces:
        pressure : (1.53616e+06 -8.31049e+06 8.5446e+07)
        viscous  : (-8765.28 -9046.1 -50774.7)
        porous   : (0 0 0)
    sum of moments:
        pressure : (-8.21122e+07 -1.51684e+08 -5.71578e+07)
        viscous  : (-658439 -1.10143e+06 434125)

I ran this same case with only pitch (z-plane=0) and heave at 12knots same mass and other parameters.. It ran for 250 sec; didnt converge ;still running. I will add the animation as well.

Can I use openfoam for such big case? if yes what am I doing wrong.
Thanks!