FUNDAMENTAL RESEARCH ON MECHANISM OF CAPSIZING OF SHIPS IN WAVES

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In considering the safety plan of the ship, it is important to treat the motions of the inclined ship in waves. When a ship is inclined at an arbitrary angle due to the effect of strong wind or shift of cargo etc., the ship's cross section under the water line is asymmetry. Therefore the coupled effects between symmetric motions and anti-symmetric motions can not be ignored.These the effects was investigated by equation of inclined ship motions and tank test using ship model.In the experiments, it was observed that the inclined ship rolls with large angle in bow sea condition.To develop an analytical method for capsizing of the ship with bulwark, experiments for capsizing of two-dimensional bodies with the bulwark was carried out in regular transverse waves.The experimental results show that capsizing of two-dimensional bodies was caused by the quantity of shipped water on the deck and the effects of bulwark height.The dynamic swell-up due to the disturbance of orbital motion of water particles on the ship's sides in the oblique waves was investigated theoretically.Model experiments on the dynamic swell-up due to the oblique waves were carried out for a ship model with the Lewis form cross sections fixed in the oblique waves. Another model experiments on the safety of ships in the waves were carried out for that ship model and a model of fishing vessel.If deck wetting occurs repeatedly, some amount of shipping water is accumulated on deck. In this situation, stationary oscillation around heeling condition and/or capsizing of the ship occur in waves.