CFD Online Discussion Forums - Flux not conserved in cyclicAMI interfaces if areas are different

Hello,

currently, a cyclicAMI interface between two patches does not conserve the (mass/volumentric) flux, if the patches have different areas. The velocities are transferred from one side/patch of the interface to the other.

In constant/polyMesh/boundary, the definition of such an interface looks like

Code:

    one_side_of_interface

    {

        type            cyclicAMI;

        inGroups        1(cyclicAMI);

        matchTolerance  0.0001;

        transform       noOrdering;

        neighbourPatch  other_side_of_interface;

        nFaces          4949;

        startFace       12612869;

    }

    other_side_of_interface

    {

        type            cyclicAMI;

        inGroups        1(cyclicAMI);

        matchTolerance  0.0001;

        transform       noOrdering;

        neighbourPatch  one_side_of_interface;

        nFaces          4949;

        startFace       12612869;

    }

and in the velocity boundary conditions, e.g. 0/U

Code:

    one_side_of_interface

    {

        type            cyclicAMI;

        value           uniform (0 0 0);

    }

    other_side_of_interface

    {

        type            cyclicAMI;

        value           uniform (0 0 0);

    }

So let's say, one side of the interface uses tetrahedrons and the other hexahedrons and the areas of the two sides differ by 5 %, the velocity will be the same on both sides, but the mass flux (or for incompressible solvers the volumetric flux) will also differ by 5 %.

Now I would like to understand, how cyclicAMI is working in this case at the moment:

Is it correct, that the values of the two sides of the interfaces are exchanged in methods

Code:

void Foam::cyclicAMIFvPatchField<Type>::updateInterfaceMatrix

in cyclicAMIFvPatchField.C?
https://github.com/OpenFOAM/OpenFOAM...FvPatchField.C

Is this the actual code, where the values are transferred from one side to the other?

Code:

    forAll(faceCells, elemI)

    {

        result[faceCells[elemI]] -= coeffs[elemI]*pnf[elemI];

    }

So in coeffs, the weights between faces of the patch of one side and the faces on the patch of the other side are stored?

If you would like to create a new boundary condition to conserve the fluxes, in a first step, I would modify these weights with the ration of the areas of the two patches?

Where are the weights calculated?
In void Foam::cyclicAMIFvPatch::makeWeights(scalarField& w)?
https://github.com/OpenFOAM/OpenFOAM...IFvPatch.C#L79

So there different weights for the two patches? If this would be the correct place to add a area ratio, there would also one area ratio for one patch and the inverse for the other side?

Thank you for any help?
Joachim