[jiadongw]

Hey Foamers,

I'm trying to add a linear spring to the floatingObject tutorial.

Here is my modified dynamicMeshDict for this tutorial, where I added the restraints.

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      motionProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dynamicFvMesh       dynamicMotionSolverFvMesh;

motionSolverLibs   ("librigidBodyMeshMotion.so");

motionSolver       rigidBodyMotion;

rigidBodyMotionCoeffs
{
    report          on;

    solver
    {
        type Newmark;
    }

    accelerationRelaxation 0.7;

    bodies
    {
        floatingObject
        {
            type            cuboid;
            parent          root;

            // Cuboid dimensions
            Lx              0.3;
            Ly              0.2;
            Lz              0.5;

            // Density of the cuboid
            rho             500;

            // Cuboid mass
            mass            #calc "$rho*$Lx*$Ly*$Lz";
            L               ($Lx $Ly $Lz);
            centreOfMass    (0 0 0.25);
            transform       (1 0 0 0 1 0 0 0 1) (0.5 0.45 0.1);

            joint
            {
                type            composite;
                joints
                (
                    {
                        type Py;
                    }
                    {
                        type Ry;
                    }
                );
            }

            patches         (floatingObject);
            innerDistance   0.05;
            outerDistance   0.35;
        }
    }
         restraints
         {
               verticalspring
               { 
                     body                     floatingObject;
                     type                     linearSpring;
                     anchor                   (0.5 0.35 0.1);
                     refAttachmentPt          (0.5 0.45 0.1);
                     stiffness                100;
                     damping                  0;
                     restLength               0.1;
               }
          }
}


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

That’s the only thing I changed. But the cases blow up after several time steps.

Does anyone have the relevant experience with this tutorial?

Any advice is appreciated, thanks.

[jinheng]

Originally Posted by jiadongw

Hey Foamers,

I'm trying to add a linear spring to the floatingObject tutorial.

Here is my modified dynamicMeshDict for this tutorial, where I added the restraints.

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      motionProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dynamicFvMesh       dynamicMotionSolverFvMesh;

motionSolverLibs   ("librigidBodyMeshMotion.so");

motionSolver       rigidBodyMotion;

rigidBodyMotionCoeffs
{
    report          on;

    solver
    {
        type Newmark;
    }

    accelerationRelaxation 0.7;

    bodies
    {
        floatingObject
        {
            type            cuboid;
            parent          root;

            // Cuboid dimensions
            Lx              0.3;
            Ly              0.2;
            Lz              0.5;

            // Density of the cuboid
            rho             500;

            // Cuboid mass
            mass            #calc "$rho*$Lx*$Ly*$Lz";
            L               ($Lx $Ly $Lz);
            centreOfMass    (0 0 0.25);
            transform       (1 0 0 0 1 0 0 0 1) (0.5 0.45 0.1);

            joint
            {
                type            composite;
                joints
                (
                    {
                        type Py;
                    }
                    {
                        type Ry;
                    }
                );
            }

            patches         (floatingObject);
            innerDistance   0.05;
            outerDistance   0.35;
        }
    }
         restraints
         {
               verticalspring
               { 
                     body                     floatingObject;
                     type                     linearSpring;
                     anchor                   (0.5 0.35 0.1);
                     refAttachmentPt          (0.5 0.45 0.1);
                     stiffness                100;
                     damping                  0;
                     restLength               0.1;
               }
          }
}


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

That’s the only thing I changed. But the cases blow up after several time steps.

Does anyone have the relevant experience with this tutorial?

Any advice is appreciated, thanks.

hello， jiadong
I meet similar problem too, do you have any suggest after your question.

[jiadongw]

Originally Posted by jinheng

hello， jiadong
I meet similar problem too, do you have any suggest after your question.

Sorry, I'm still confused about the restraints in rigidBody motion solver.

I guess the key point is how to define the centre of mass and transform. But I did not find some reference materials about that.