A nonlinear 7-DOF model for U-tanks of arbitrary shape

This work presents a novel nonlinear 7-DOF model for ships equipped with U-tanks of arbitrary shape. The model uses the standard six degrees of freedom for the ship, in addition to a single degree of freedom for the tank fluid. The ship–tank interaction was modeled with Hamiltonian (analytical) mechanics, end external forces (such as those due to the surrounding ocean, actuator forces and various damping forces) were added later in a Newtonian framework. These external forces were not explicitly modeled in this work. The model was compared to two (significantly simpler and less powerful) models in the literature, one of which was experimentally verified. Under the same assumptions, the new model is identical to the experimentally verified one, and contains several effects not found in the other.

► Using Hamiltonian (analytical) mechanics, we model a u-tube anti-roll tank.
► The nonlinear, 7-DOF model is valid for arbitrarily-shaped U-tanks.
► The model is compared to two existing (simpler) models from the literature, showing very good match under similar assumptions.