[adubois]

I am modelling a heaving and pitching foil using an inner grid around the foil which moves using a define_zone_motion udf (grid within zone does not deform) and an outer grid which deforms according to the motion of the inner grid (defined using a define_cg_motion udf). The second and third image show results of the motion on a very coarse grid (motion shows the wanted behavior).

The problems start when I use a proper grid (meaning a refined grid, using much more node). The outer grid does not deform as wanted and will results in negative cell volumes. This problem is in my opinion caused by the fact that the lines in the outer grid do not deform a straight lines as wanted but get a curve in them (as can be seen in the first image). Anyone suggestions in how to resolve this issue?

Thanks in advance

PS If you would want more information or a video of the motion (to better understand the problem), leave your email adres and i will try to respond as good as possible

[ndabir]

I have a similar problem? did you find what is the solution to it?

[adubois]

I did not find a solution, I used a unstructured grid in the outer region and allowed for remeshing and solved it that way.

[stumpy]

Do you have rotations for the inner mesh region, or just translations? If you have rotations the I would use a non-conformal interface between the two regions and allow sliding, so the rotational components don't get passed to the outer mesh.