Fluid Structure Interaction -- Convergence Problem

Hello,

I am working with the FSI module and I am trying to model an oscillating plate in an infinite expanse of fluid. I have successfully used the "sliding wall" boundary condition to do this, but when I instead make a solid plate in the geometry and prescribe an oscillating motion I get convergence problems (solver diverges after about 2-3 oscillations).

The reason I need the geometric model to work is because I plan on adding more complexity to the oscillating shape (namely rigid posts) but I can't hope to do that until I get the simplest case of the geometry to behave well first.

I have a feeling that the solver is taking large time steps at the beginning which is creating some error that is then propagating and causing the model to diverge. Is there anything I can change in the solver? I have tried modifying the default FSI solver type from "constant (Newtonian)" to "Automatic (Newtonian)" which seemed to delay the divergence some, but not prevent it entirely.



Attached is the project file and an image of my solver error plot, any input is appreciated!

Thanks,
Trevor

mph: www.fileswap.com/dl/ysSCvetUIT...ing_flat_plate_Model2.mph.html