Experimental Research On 300000 DWT Mooring Oil Tank Under Long-period Waves

With the rapid economic development and ships become large,open terminals have become the first choice for port construction.However,the environment conditions in open waters are very complicated.The most obvious feature is that the wave period is long,and the moored ship is more sensitive to low-frequency long-period waves,which makes the moored ship produce greater movement and causes risks for the mooring operation and safety.Therefore,the mooring safety of moored ships under long-period waves has become a hot issue of current research.However,moored ships under long-period waves will also have different motion characteristics under the influence of different water levels,load levels and wave directions.Therefore,the influence of long-period waves on the motion of moored ships is systematically studied,and it is valuable for mooring safety.This thesis systematically study the 300000 DWT Mooring Oil Tank under long-period waves based on physical model tests.The research results show that the movement of the moored ship under different working conditions increases with the increase of the period.The sway,roll,heave and yaw moments is more sensitive to the natural period of mooring ships,and the surge and pitch motions are less sensitive to it.Compared with full load,the movement under ballast is bigger,but the amount of surge and pitch movement are greater under full load,because when the mass of the ship is large,the moored ship has greater inertia.Long-period waves have larger wave energy,and the amount of motion under ballast is more obviously restricted by motion in other directions.The heave is positively correlated with the ratio of the wavelength and the length of the ship.The heave motion increases with the increase of the wave period,but when the heave of the moored ship increases to be identical to the wave height,the heave reaches the maximum value.This is more obvious for full loaded with high water level and vertical wave attack.When the wave period is close to the multiple of the mooring ship's rolling and pitching natural period,it is more likely to cause the moored ship to produce resonant motion and cause a rapid increase in motion.The mooring force is more obviously affected by the wave period,and the mooring force increases with the wave height in a power order,and the growth rate is faster under long-period waves.SSecondly,the mooring force is produced by the movement of the mooring ship,which is basically consistent with the change law of the movement.The bow and stern cables are most affected by yaw motion.The transverse cables are mainly affected by sway and roll movement,while the reversed cables are mainly affected by surge and pitch movement.When a mooring ship is under the action of vertical waves attack,the main force cable is a transverse cable.Under the action of horizontal waves,the main force cable is an inverted cable.The mooring force generated by the vertical wave is greater.Finally,based on the sway and surge as the evaluation criteria for operation and the maximum mooring line forces as the evaluation criteria for safety,the reference wave conditions and danger warning are proposed.By analyzing the most unfavorable conditions,the calculation formulas for the movement and the mooring force and the mooring safety standards are given.The research results in this thesis have certain reference significance in actual engineering design.