[jiadongw]

Hey, Foamers

I try to simulate a flapping foil with only heave motion using solidBody motion solver.

When the heave amplitude is relatively small, everything seems to be fine. But when the heave amplitude is large (eg. equal to chord of foil), the field become wrong, as shown in attached figture.

My questions are:

1)Does this problem is caused by the large deformation of mesh? I'm not sure about that.
2)If it is due to the mesh deformation, is there any method to handle it?

The dynamicMeshDict is:

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

dynamicFvMesh   dynamicMotionSolverFvMesh;

motionSolver    interpolatingSolidBody;

patches         (AIRFOIL);

innerDistance   0.3;
outerDistance   4;

CofG            (0.42 0 0);

solidBodyMotionFunction multiMotion;

heave
{
    solidBodyMotionFunction oscillatingLinearMotion;
    oscillatingLinearMotionCoeffs
    {
        amplitude       (0 1 0);
        omega           6.2832;
    }
}

pitch
{
    solidBodyMotionFunction oscillatingRotatingMotion;
    oscillatingRotatingMotionCoeffs
    {
        origin          (0.2 0 0);
        omega           6.2832;   
        amplitude       (0 0 0);
    }
}



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

Thank you.

[saifullahkhalid]

Yes, this happens due to the skewed cells in the vicinity of the airfoil. Overset mesh may be a better way to handle it. You can also try different setting parameters for the mesh motion solver, such as the displacementLaplacian etc.