Experimental Study on Yaw Moment in Shallow Water Turning assisted by Tugs based on Turning Short Around of Actual Large Vessel in Ports and Harbors

Abstract

　In order to achieve a head-out mooring, instead of a head-in mooring ordinarily conducted in larger ships, as a countermeasure of a quick evacuation for large ships against a great earthquake and tsunami, it is important to investigate and obtain a property of yaw moment acting on the ship in shallow water during a turning short around assisted by tugs. From several pure yaw rotating tests conducted in this study, it is found that the yaw moment is increased rapidly in a shallow water where the ratio(h/d) of water depth(h) and draft(d) is less than 2.0, and that during accelerated situation is larger than that during the steady situation. The yaw moment has a steady value during the turning, which corresponds to the rotating angular velocity, at h/d ≧ 2.0, and is also significantly influenced and varied by the attitude of the ship in the turning basin at the shallow water; h/d < 2.0.