A Comparative Study on the Motions of a Mooring LNG Ship in Mixed Waves and Long-period Waves Respectively

摘要

A series of physical model experiments have been performed to conduct a comparative study on the motions of a mooring ship. The mooring ship employed in the experiment is an LNG ship under the transverse action of mixed waves and long-period waves respectively. The prerequisite of such a research is that the total energy of the mixed waves should be equal to the long-period waves. The experimental results show that with the increase of low-frequency spectral peak period, the laws of a mooring ship's motion are almost unchanged under the action of three different kinds of bimodal waves. With the variation of spectral peak period, similar situations happened to the laws of the mooring ship's motion under the action of long-period waves. The low-frequency energy of mixed waves has command of the motions of a mooring ship (except the movement of pitch). When is ratio of the low-frequency energy accounts for 20%, the mooring ship's movements in mixed waves will change within the range from 0.5 to 0.6 times of its movements in long-period waves. When the low-frequency energy accounts for 50%, the range will be within 0.7 to 0.8 times. When the low-frequency energy accounts for 80%, the range will be within 0.85 to 0.95 times.