Studying And Simulation Of Very Large Ships Course Keeping Ability In Wind

It is difficult to avoid affecting by the wind, wave, current and other external environment when ship is under way. The ship may have six degrees of freedom of movement state. These are detrimental for ships'safe navigation, and the yaw will change the ship's course, so that it can not navigate on the predetermined course. Especially when the ship sailing in the waterway or harbor, due to ship speed, water's width and depth and other restrictions, it is essential to keep the ship on a certain course. Based on the domestic and foreign research data, the paper established a mathematical model for very large container ships and ore/bulk carriers. The very large ship's course keeping ability in wind using rudder was mainly researched in the paper. Considering the ship type, ship speed, wind speed, wind direction, loading condition and the effect of shallow water on the course keeping ability, and solving the mathematical model approximately, obtained estimation formula of rudder angle for course-keeping and wind limitation for course-keeping.For Kijima hydrodynamic model having considered the affection of modern ship such as container ships and ro-ro ship, at normal speed, hydrodynamic forces were calculated using Kijima model. The simulation results of turning of very large ships show that the mathematical model can more accurately describe the motion.Very large ships will loss the rudder effect even speed is higher than other ships. The paper does not take into account ship motion under low-speed domain. When the speed is lower but ship can maintain rudder efficiency, the effect of shallow water is considered. Through modifying the shallow water hydrodynamic derivatives, the paper realized the simulation of turn in shallow water. Simulation results quantitatively and qualitatively reflect the performance of shallow water on course keeping ability.If suddenly affected by the wind, the ship will change its original course. In order to maintain the original course, we need steering to deflect suppression. For ease of simulation, a simple PID controller is used as the command rudder angle input and it achieve a better control effect. This research quantitatively and qualitatively descript very large ship's course keeping ability in wind and provide a practical guide for officer to learn course keeping ability of very large ships. It provides a theoretical reference for safety assessment of very large ships steering in wind. It also provides a theoretical foundation for simulation method of researching very larger ship's characteristic of motion in wind.