On a Mathematical Model of Maneuvering Motions of Ships in Low Speeds

Abstract

A mathematical model has been already established for describing maneuvering motions of ships with relatively large advance speeds. But this model is not applicable to the motions in low speeds, though such motions are of vital importance for ships' safety in harbours. In the present report, an attempt is made to modify the above mathematical model so that it can also express maneuvering motions in low speeds.Utilizing the large-amplitude planar motion mechanism, detailed captive model tests were carried out for two tanker models and a boxtype vassel. To cover various aspects of maneuvering motions, wide combinations of longitudinal and lateral speeds and yawing velocity were employed in the tests. The test results, mainly of a tanker model, are introduced and the method is discussed to describe hydrodynamic forces in simple forms. Starting from the established mathematical model in relatively large advance speeds, some terms of the model are modified from necessity so that it can express hydrodynamic forces in wide combinations of three motions. After these efforts, a new mathematical model is summarised finally. It is needless to say that the model was led, being based on open-water characteristics of hull, propeller, rudder and interaction effects among them.