Experimental and numerical investigations on responses of ship rolling motion coupled with liquid sloshing inside three tanks with and without baffles

Rolling response of a floating production storage and offloading coupled with sloshing inside three liquid tanks with and without baffles under different wave periods is analyzed experimentally in a towing tank. The main focuses of this study are to examine the effect of baffles on natural period and amplitude of ship rolling motion coupled sloshing for various tank filling depths. The experimental results show that baffles decrease the natural period of ship rolling motion for low filling conditions (20% and 30%). However, when the filling depths are high (e.g., 60% and 70%), the natural period is increased due to the installation of the baffles. The changing of natural period is revealed quantitatively by the change of the sloshing-induced added mass calculated by the numerical potential flow model. The amplitude of ship rolling motion coupled with sloshing without baffles reveals two typical phenomena, namely the anti-rolling effect at low filling conditions and the enhanced-rolling effect at high filling conditions, depending on the dominant factor between the hydrostatic and the hydrodynamic forces. Baffles are effective in suppressing the amplitude of ship rolling motion, especially at its natural period. Their effect is more obvious for low filling condition than that for high filling conditions. This is because baffles are more effective in stopping the fluid inside the tanks from flowing to the inclined side when the filling depth is low. It is also found that baffles can decrease the sloshing-induced mass at low filling conditions and increase that at middle and high filling conditions. The above-mentioned changes are the reasons for the decrease and increase in the natural period of ship rolling motion at low and high filling conditions, respectively, due to the application of baffles.