Hello,
I am trying to simulate the water-exit process for a submerged vehicle, in the presence of ocean waves. I have run into some issues with the VOF and the 6-DOF behaviour. Firstly, when the vehicle is fully out of the water, the first cell or two on the surface of the vehicle have a volume fraction correspoding to that of pure water, then there is a hard jump to pure air, rather than a continuous change in volume fraction. Also pertaining to the VOF issues, a considerable amount of my water phase is being generated in steps during the run. Secondly, the forces from the 6-DOF solver do not converge very well in the water. For now, I have limited the vehicle to 3-DOF, being vertical translation (z), wave propagation direction translation (z), and rotation in the xz plane. I believe this is due to added mass instabilities, as I increased the mass of the vehicle and this decreased the amplitude of the spikes in the solution. I have dropped the timestep very low and it hasn't changed my result; and I think my mesh is okay, the background has a refined region where the sea surface is, and the overset mesh has no warnings about quality. My average y+ on the vehicle walls is about 80, which is around what I intended it to be. I am aware of the implicit mesh update function to help with the 6-DOF motion, however this takes so long that I would rather find another solution if possible. Thank you for any assistance.
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