Experimental study of a mooring ship's motion responses in mixed waves

By employing the method of bimodal spectrum to simulate the mixed waves that swell and wind wave appearing at the same time,the experiments were performed for a 266,000 m3 LNG ship moored to an island berth.A special effort was made to measure the mooring ship's motion responding the mixed waves.The result shows that when the energy of mixed waves is definite,the movement of the mooring ship will generally increase with the increase of low-frequent wave energy;when the loading condition is fixed,the surge and heave of the mooring ship will increase with the increase of period of swells in mixed waves.The peak values of sway,roll,and yaw are in proportion to the natural roll period of the mooring ship.When the condition of wind waves in mixed waves is definite,the movement of the mooring ship will rapidly increase with the increase of wave height of swells in most cases.When the condition of swells in mixed waves is fixed,the changes of wave height of wind waves have small effect on the movement of the mooring ship.In transverse waves,the pitch of the mooring ship is little influenced with the changes of mixed waves.