The Research On The Sea-Keeping And Floating State And Stability Of A 15,000-Ton Semi-Submerged Vessel

Semi-submerged vessel is a kind of special ships for transporting over-large cargo. Its width is very large and the radio of its principal dimensions is far more different than that of other vessels, and thus has its unique characteristics. When a semi-submerged vessel is carrying a large cargo, the center of gravity of the whole system is high, and it is very easy to be attacked by the wave and its sea keeping is bad. many accidents have happened in the history of semi-submerged vessel transportation engineering. In order to ensure the safety of the ship and the good, it's necessary to calculate and analyze the ship's hydrodynamic characteristics and motion response to research its sea keeping.Besides, the stability of a ship has an important effect on its safety. When over-large cargo is loaded on the deck, the center of gravity of the ship system is very high, which makes a bad effect on the stability. In addition, ballast tanks are distributed throughout the main body, the free surface effect of which reduce the stability. Therefore, the floating state and stability of its operational configuration and state directly effect the safety of the cargo and economic benefit of the operating company.In this paper, the sea keeping and floating state and stability of a 15000-ton semi-submerged vessel are studied. Firstly, the sea keeping of the ship under typical sea state is researched. Based on 3D potential theory, the hydrodynamic characteristics and motion response of the ship under zero speed are calculated and analyzed by SESAM, a general analysis programme of calculation of wave-structure interaction. Besides, the short-term prediction of the sea keeping of the ship has been done related to the typical sea state in domestic offshore navigation area that the ship navigates on, including the mean of one third of the largest response, most probable largest response level and the probability of the shipping of green water.Secondly, the floating state and stability of the ship is studied. By NAPA software, the hydrostatics dates are calculated to research its buoyancy characteristics. Then KG-limit curve is calculated to evaluate its cargo capacity. The intact stability is checked in accordance with the relevant rules. At last the method of improving the ship's stability as well as the intact stability criteria of the semi-submerged vessel are suggested.