On the response function for rolling motion of fishing boat among ocean waves

Abstract

Usually fishing boats or research ships drift among ocean waves and stop their engines during their operation in fishing or oceanographic work. It would be valuable to investigate the rolling response of the vessel to ocean waves for the purpose of safety performance of operations while stopping at sea. As a matter of fact, it is very difficult to determine the characteristic of ship's response to motion actually in the sea by means of compulsive forces which are given artificially. If there is a way to get the characteristic response of the ships to the motions by measuring ocean waves and ship motions in actual sea, this will be the most useful method of studying the ship's motions in a seaway. This paper describs the way of the above mentioned motions using model ship experiments which were performed in an experimental tank in which waves were produced by the irregular wave generator as in a seaway. The characteristic for the ship's rolling motion was deduced by analysis of the stochastic process on the results of observation, using cross correlation coefficient for wave slopes as input forces and rolling angles as out-put forces in the ship's dynamical system.