[courant_numero_uno]

Hello,


I am using foam-extend-4.0. I have a simulation working using the movingCylinderInChannelIco tutorial, which uses the immersed boundary method. The dynamicMeshDict uses immersedBoundarySolidBodyMotionFvMesh:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | foam-extend: Open Source CFD                    |
|  \\    /   O peration     | Version:     4.0                                |
|   \\  /    A nd           | Web:         http://www.foam-extend.org         |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// dynamicFvMesh   staticFvMesh;
dynamicFvMesh   immersedBoundarySolidBodyMotionFvMesh;

immersedBoundarySolidBodyMotionFvMeshCoeffs
{
    motionFunctions
    (
        cylinder
        {
//             solidBodyMotionFunction     translation;
//             translationCoeffs
//             {
//                 velocity (0.1 0 0);
//             }

            solidBodyMotionFunction     linearOscillation;
            linearOscillationCoeffs
            {
                amplitude    (0 0.3 0);
                period       1.5;
            }
        }
    );
}


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

However, I would like to calculate the motion of the cylinder rather than define it. Specifically, to simulate vibrations using a spring restraint. For example, I have a dynamicMeshDict using dynamicMotionSolverFvMesh, which works:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1812                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dynamicFvMesh   dynamicMotionSolverFvMesh;

//staticFvMeshCoeffs
//{
//}

motionSolverLibs ( "libsixDoFRigidBodyMotion.so" );

solver          sixDoFRigidBodyMotion;

//diffusivity     quadratic inverseDistance 1 ( cylinder );

sixDoFRigidBodyMotionCoeffs
{
    patches         ( cylinder );
    
    innerDistance   0.05;
    
    outerDistance   0.7;
    
    
    centreOfMass    ( 0 0 0 );
    mass            75.362562415;
    g               ( 0 0 -9.8065 );
    momentOfInertia ( 2.7874e+08 5.8901e+08 6.6762e+08 );
    velocity        ( 0 0 0 );
    rho             rhoInf;
    rhoInf          1.225;
    accelerationRelaxation 0.5;
    //accelerationDamping 0.95;
    report          on;
    reportToFile    on;
    solver
    {
        type            Newmark;
    }
    constraints
    {
        onlymoveiny
        {
            sixDoFRigidBodyMotionConstraint     line;
            direction                            (0 1 0);
        }
        
        norotation
        {
            sixDoFRigidBodyMotionConstraint     orientation;
        }
        

    }
    restraints
    {
        spring
        {
            sixDoFRigidBodyMotionRestraint        linearSpring;
            anchor                                (0 1.8 0);
            refAttachmentPt                        (0 0 0);
            stiffness                            40000;
            damping                                3.47246454;
            restLength                            1.8;
        }
    }
}

/*
dynamicFvMesh      dynamicMotionSolverFvMesh;

motionSolverLibs ("libsixDoFRigidBodyMotion.so");

motionSolver    sixDoFRigidBodyMotion;

diffusivity        quadratic inverseDistance 1 ( cylinder );

patches         (cylinder);
innerDistance   0.3;
outerDistance   1;

mass            4;
centreOfMass    (0 0 0);
momentOfInertia (1.958864357 3.920839234 2.057121362);
orientation
(
    0.9953705935 0.09611129781 0
    -0.09611129781 0.9953705935 0
    0 0 1
);


g               (0 -9.81 0);
rho             rhoInf;
rhoInf          1;
report          on;

solver
{
    type symplectic;
}

constraints
{
    fixedLine
    {
        sixDoFRigidBodyMotionConstraint fixedAxis;
        axis (0 1 0)
    }

    zAxis
    {
        sixDoFRigidBodyMotionConstraint axis;
        axis                (0 0 1);
    }
}

restraints
{
    verticalSpring
    {
        sixDoFRigidBodyMotionRestraint linearSpring;

        anchor          (0 1.8 0);
        refAttachmentPt (0 0 0);
        stiffness       4000;
        damping         2;
        restLength      1.8;
    }
}

*/ 


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

Is it possible to implement restraints and solid body motion solvers into the immersed boundary method? How would I accomplish this?


Thanks!

[courant_numero_uno]

To answer my own question, there is a good tutorial here:


http://www.tfd.chalmers.se/~hani/kur...eirsson/OF.pdf


Though I had some issues with the code which I posted about here:

OpenFOAM Immersed Boundary Method - forceBased motion class creation


Additionally, this tutorial seems to encounter issues with the forces jumping sporadically.. believe this issue is due to the way the code uses loops. In my code, I implemented an "acceleration relaxation/damping" which sort of helps mitigate the sudden jumping, but I'm still working on getting it to run smoothly.

[andrewbickerdike]

Hi,

Did you manage to get this code working?

Thanks.