Performance prediction of a planing craft by dynamic numerical simulation

This paper presents mathematical models for the dynamic simulation of a planning craft and a waterjet propulsion system. The models, developed in a Matlab-Simulink software environment, are structured in modular form, in order to describe the various elements of the system as individuals blocks (hull, prime mover, gear, waterjet, etc.), taking into account their interactions. In this way it is possible to characterise the dynamic behaviour of both the single components and of the whole propulsion plant. The module of the planning behaviour of a craft is a new feature of the general dynamic simulation model already developed by the authors. With this new module it is possible to account for the resistance and trim variation during boat acceleration in order to properly catch the interaction between the planing hull and the propulsion system. The waterjet model, already presented in previous papers, has been recently improved in order to take into account the waterjet pump efficiency variation according to the different operating conditions. The developed model is able also to take into account the effects of the cavitation on the waterjet performance. The waterjet propulsion model has been validated both in steady state and transient situations through comparisons with data provided by waterjet manufacturers. An application has been made for the prediction, at a design stage, of the acceleration performance of a waterjet propelled small craft.