Numerical modelling of propulsion, control and ship motions in 6 degrees of freedom

This work presents the main steps for the development of a multi-physic simulation platform, able to represent the dynamics of a twin-screw ship in 6 degrees of freedom, taking into account the complete propulsion system including automation effects. The simulation platform has to be used in the preliminary design phase in order to study and design the propulsion plant and its control system. The ship motion model has been developed including roll motion, in order to capture the ship heel angles during tight turning circles, which may be significant for a fast naval vessel. Moreover, the simulation model includes a simplified representation of the asymmetric behaviour of the two propeller shafts during manoeuvres, which cannot be neglected when dealing with the propulsion plant behaviour. Several sub-models have been developed and calibrated by means of a set of experimental tests, in model and full scale. The sea trial campaign is finally used to validate and tune the developed simulator; thus, the final version may be adopted as an optimization tool for other future designs (or sister ships) and training purposes. Although the presented case study has been validated on a specific ship, most of the discussed models have a general application.