[David712]

I got a problem when I simulated the rotation of the vessel. There are two kinds of simulations I can make are:1. Forced rotation based on the overlap mesh, I mean give a propulsion force along the X axis, and the ship will rotate in a fixed circle; 2. Freed the DOF(degree of freedom) with a incoming flow;

But now if I combine two of these, here comes the problems: when the translation degrees freedom of the x and y axis are freed, z axis is fixed and the rotation freedom is only for rolling, the simulation result is quite wield that when the ship moves, the ship also pitch while this freedom is not turn on, with the pitch movement become acute, the bow finally plunge into the water. I don't know why this situation would happened.