Study Of Motions Of 300t Class Coastguard Ship Advancing In Waves

Coastguard ships play an important role in neighboring sea confliction,ocean rights protection,and ocean power construction.It requires the coastguard ships with good performance in resistance,stability and seakeeping characteristics.Severe motion,green water on deck,propeller racing have a series of harmful effects on the ships.Ship motion in waves has gradually become a major index for design assignment of Coastguard Ships.In this thesis,the motion performance on beam sea for zero speed,head sea for a speed of 300 t Class Coastguard Ship is studied.Based on the Strip theory and the 3D potential theory,using the software of SEAKEEPER and WALCS to calculate the motion responses at zero speed,low-speed,medium-speed and high-speed in regular wave.The prediction accuracy of two kinds of theory for high speed slender ship in various speed are analyzed after comparing with model test results.3D potential theory is Suitable for roll of beam sea at zero speed.Strip theory predictions including transom terms are closest to the experiment results for pitch and heave,at the highest Froude number(F(28)641.0n)predictions are also reasonable.Using the theory of stationary random process of linear system,considering the ship mission area selected the JONSWAP wave spectrum which is suitable for limited wind path offshore waters to solve the ship motion response spectrum density function in the random sea waves.Calculating the significant amplitude of 2~6 SST,predicting the probability of dangerous events such as green water on deck,slamming,propeller racing and so on.Checking the motion performance and the MSI by criterions of Surface ship rules and ISO 2631.The ship design meets the requirements of rules and design specifications.Considering the ship navigation safety and Comfort of crew,suggestions are given for the ship should slow down in the high sea condition.