Numerical Analysis of the Ship Propulsion Control System Effect on Manoeuvring Characteristics in Model and Full scale

A comprehensive approach to simulate the interaction between the ship propulsion system and manoeuvrability, during transients and off design conditions, is presented. The increasing attention on the manoeuvring features of the vessel has forced designers to consider this aspect already in the preliminary stages of the project. Data about manoeuvring characteristics may be obtained by means of several model tests (at planar motion mechanism or with free running models). However, differences between model tests and full scale trials exist. From the hydrodynamic point of view, some disagreements are due to the scale effects but also the effect of the propulsion control system, highly non-linear, may provide a considerable contribution to such differences. These dynamical aspects cannot be taken into account with traditional methodologies and purely stationary approaches. For these reasons, the ship dynamic behaviour is evaluated by time domain simulators, developed by the authors, which include the ship dynamics, the propulsion plant dynamics and the propulsion control system logics. At the end of the paper some simulation results are shown in order to better understand the effects and the differences of the propulsion control settings on the ship manoeuvrability in model and full scale