Waterjet Propulsion System Performance Prediction by Dynamic Numerical Simulation

Abstract: This paper presents an improved version of a mathematical model developed by the authors for the dynamic simulation of waterjet propulsion systems. The model, developed in a Matlab-Simulink software environment, allows to obtain information on the propulsion system performance both in steady state conditions and especially during transient situations (manoeuvring conditions). Because of its modular arrangement, the various elements of the propulsion chain (hull, prime mover, gear, waterjet, etc.) are described as individuals blocks, which are linked together in a proper way taking into account their interactions. In this way it is possible to simulate the dynamic behaviour of the whole propulsion plant and of the single components. The model may be used also to easily investigate the influence of some design parameters on the system performance. As compared with the previous published version, the present improved model includes the wake fraction evaluation, based on the simulation of the flow ingested by the waterjet inlet, whose velocity is determined taking into account the growth of boundary layer over the hull. The model has been tested and validated by means of comparisons with experimental data given by an important waterjet manufacturer.