An Experimental Study of the Coupling Between Roll Motion and Sloshing in a Compartment

In this paper an experimental investigation on the coupling between the roll motion of a ship in a regular beam sea and the sloshing of a free surface liquid in a compartment is presented. A large scale ship model equipped with a floodable compartment has been tested. The amount of the shipped water in the compartment has been kept constant during any single test but four different degrees of filling have been considered. To emphasize the effect of the free surface of the liquid in the container, the frozen liquid condition has been tested as well. The roll history has been recorded by the use of an inclinometer, while four level transducers inside the compartment and a videorecording setup have provided the sloshing history. The obtained results are meaningfull and confirm the importance of an improvement in the modelling of sloshing loads for both hydrodynamic and structural safety. A good forecasting of the roll amplitude of the ship has been obtained by the use of a traditional non-linear roll motion equation accounting for the induced sloshing moment in the RHS: a nonlinear free surface / fully moving panels routine provides the required moment. The dangerous frequencies are well captured and the predicted roll amplitudes and the free surface behaviour compare well with experiments. An improvement of the code to take into account both the large amplitude viscous sloshing and the coupled roll-sway-heave motion is in progress.