ANALYSIS OF HYDRODYNAMIC SOURCES IN NOISE PROBLEMS ON BOARD HIGH SPEED SHIP

With the increase of the ship speed, flow noise sources can be responsible for an amplification of the total noise level on board new generation of fast ships. In particular, the turbulent boundary layer (TBL) excitation, generally considered in the study of internal and external noise radiation problems of aircraft and underwater marine vehicles, is here analysed for fast surface ships. Due to the high computational cost associated to the numerical evaluation of wall pressure fluctuations at high Reynolds number and to the difficulties related to full scale measurements, it is not easy to obtain pressure spectra representative of real conditions. In this context, it is of great importance to develop predictive theoretical models for wall pressure fluctuation (WPF) spectra representation. It is important to point out that the presence of the free water surface can produce significant pressure gradients and that, due to the relatively low velocity of marine vehicles, the subconvective components of the pressure field dominate the structure-fluid coupling. On the basis of some extensive hydrodynamic experimental campaigns performed in a towing tank, on different fast marine vehicles, for high Reynolds number values, a numerical procedure for the prediction of the full scale vibro-acoustic response of a typical ship hull structure to the TBL pressure load is presented. The dependence of the noise radiated on ship speed is here analysed.