[zweihuehner]

For a research project I want to simulate a Wave energy converter (WEC) in extreme waves with OpenFoam.
The WEC consists of two articulated floating bodies which is why I choose the overset Mesh method for modelling.

I was already able to set up a simulation with one body but I am failing to do so with two bodies (firstly without articulation).
Does anyone have experience with this? So far I just added a second object in the dynamicMeshDict like so:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2106                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dynamicFvMesh   dynamicOversetFvMesh;

solvers
{
     VF
     {
        motionSolverLibs (fvMotionSolvers);

        motionSolver            solidBody;
        solidBodyMotionFunction drivenLinearMotion;

        cellSet                 c0;
        cOfGdisplacement        CofG;
    }

    Obj1
    {
        motionSolverLibs   (sixDoFRigidBodyMotion);
        motionSolver        sixDoFRigidBodyMotion;

        cellSet         c1;

        patches         (WEC1);
        innerDistance   1000.0;
        outerDistance   1001.0;

        centreOfMass    (4 0.75 1);
        cOfGdisplacement    CofG;

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

        // Density of the solid
        rhoSolid        500;

        // Cuboid mass
        mass            #eval{ $rhoSolid*$Lx*$Ly*$Lz };

        // Cuboid moment of inertia about the centre of mass
        momentOfInertia #codeStream
        {
            codeInclude
            #{
                #include "diagTensor.H"
            #};

            code
            #{
                scalar sqrLx = sqr($Lx);
                scalar sqrLy = sqr($Ly);
                scalar sqrLz = sqr($Lz);
                os  <<
                    $mass
                *diagTensor(sqrLy + sqrLz, sqrLx + sqrLz, sqrLx + sqrLy)/12.0;
            #};
        };

        report          on;
        accelerationRelaxation 0.9;
        accelerationDamping    1;

        solver
        {
            type Newmark;
        }

        restraints
        {

            linearSpring
            {
                sixDoFRigidBodyMotionRestraint linearSpring;
                anchor            (2 0.75 0);
                refAttachmentPt   (3.75 0.75 0.9);
                stiffness         300;
                damping           0;
                restLength        1.96787;
            }

        }
    }

    Obj2
    {
        motionSolverLibs   (sixDoFRigidBodyMotion);
        motionSolver        sixDoFRigidBodyMotion;

        cellSet         c2;

        patches         (WEC2);
        innerDistance   1000.0;
        outerDistance   1001.0;

        centreOfMass    (3.4 0.75 1);
        cOfGdisplacement    CofG;

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

        // Density of the solid
        rhoSolid        500;

        // Cuboid mass
        mass            #eval{ $rhoSolid*$Lx*$Ly*$Lz };

        // Cuboid moment of inertia about the centre of mass
        momentOfInertia #codeStream
        {
            codeInclude
            #{
                #include "diagTensor.H"
            #};

            code
            #{
                scalar sqrLx = sqr($Lx);
                scalar sqrLy = sqr($Ly);
                scalar sqrLz = sqr($Lz);
                os  <<
                    $mass
                *diagTensor(sqrLy + sqrLz, sqrLx + sqrLz, sqrLx + sqrLy)/12.0;
            #};
        };

        report          on;
        accelerationRelaxation 0.9;
        accelerationDamping    1;

        solver
        {
            type Newmark;
        }

        restraints
        {

            linearSpring
            {
                sixDoFRigidBodyMotionRestraint linearSpring;
                anchor            (1.4 0.75 0);
                refAttachmentPt   (3.15 0.75 0.9);
                stiffness         300;
                damping           0;
                restLength        1.96787;
            }

        }
    }

}
// ************************************************************************* //

I found no other helping examples or code snippets dealing with the same problem except for this one: Multiple Floating Objects with 6DoF in OF 2.3.0
Unfortunately I think this solution is derived from the "twosimplerotors" example and does not allow 6DOF.


However, I can not imagine that it is not possible to simulate two floating bodies with openFoam with overset Mesh.


Looking forwards to help.

[mahsankhan]

Hey Faro Schäfer,


Did you find any solution for using more than 1 body in OpenFOAM with 6DoF? Let me know, please. Thank you so much.


Regards,
Ahsan