Estimation of full-scale ship manoeuvring motions from free-running model test with consideration of the operational limit of an engine

Abstract

Rudder effectiveness and speed correction (RSC), previously proposed by the authors, is a free-running model test method for making the manoeuvring motions of a model ship using an auxiliary thruster similar to those of a full-scale ship. In this paper, the authors propose a method for estimating full-scale ship manoeuvring motions with consideration of the operational limit of an engine (OLE), the so-called torque limit, by means of a free-running model test involving application of RSC. In this method, the control variables in RSC, namely, the auxiliary thrust and model-scale propeller rotational speed, are determined considering the change in rudder effectiveness and ship speed response caused by continuous operation at the torque limit in full scale. Numerical simulations of manoeuvring motions using the modular mathematical model in model scale with the proposed method were carried out to investigate the similarity to the corresponding full-scale ship operation at the OLE. Moreover, the authors applied the proposed method to tank tests that consist of turning manoeuvres in calm water and course-keeping manoeuvres in regular waves. The simulation results and the tank test data confirm that the proposed method can explain the effect of OLE on the variation in full-scale ship manoeuvring motions.