Increasing ship roll stability by using anti-rolling tanks

This paper shows a study on anti-rolling tank and its effects on ship roll motion. A flexible passive anti-rolling tank that consists of two fixed reservoirs, a set of three connected ducts and a set of five connected air pipes is designed for carrying out experiments. Experiments were conducted in regular sinusoidal waves of small amplitude and in irregular waves. First step, experiments are conducted in regular waves. Second step, experiments are conducted in irregular waves. For regular wave, experiments were conducted in constant wave heights and constant wave slopes. For irregular wave, experiments were conducted in two idealized wave spectrum. Those spectrum are ITTC (International Towing Tank Conference) idealized spectrum and JONSWAP (Joint North Sea Wave Project) idealized spectrum. After carrying out experiments and analysis, a view of the effects of the designed anti-rolling tank on roll motion of the model ship is shown in this paper. Both theoretical and experimental results show that when the model ship using the anti-rolling tank, the roll stability of the model ship is increased. It is recognized that the highest effects of anti-rolling tank on roll motion of the model ship in experiments with both regular waves and irregular waves are obtained when the model ship is experimented with a wave frequency nearby its natural roll frequency. At this level of the water, the natural frequency of the anti-rolling tank is also nearby the natural roll frequency of the model ship.