Estimation of the Manoeuvring Behaviour of Ship in Uniform Wind

Abstract

Wind force affects on a ship manoeuvrability, especially when the superstructure is very large or the ship's speed is much lower than the wind velocity. It is indispensable for the safety analysis of the harbor manoeuvrablity to estimate the ship motion in wind.In this paper, the predicting techiniques are investigated confirming by the successfull free-sailing model tests. Then, the manoeuvrable upper limit of wind velocity is discussed under the unsteady condition when a frequent engine telegraph is used.Through the present study, the following conclusion are obtained.(1) The numerucal simulation based on the moduler type mathematical model can give a fairly good agreement with experimental results in wind.(2) Although a dynamic yaw damping force is included in the wind force of a superstructure, it does not so much affect on the manoeuvrablity in wind.(3) From the numerical simulations with accelerating and decerelating conditions in wind, it is found that the behaviour of ship almost depends on the main engine power against the wind. This suggests that the manoeuvrable upper limit of wind velocity should be described by the ratio of main engine power to wind velocity, not by the conventional ratio of ship speed to wind velocity.