Experimental evaluation of the pressure fluctuations induced by the turbulent boundary layer on the hull of a fast ship

In last years, due to the increase of the ship performances in terms of maximum speed a lot of interest have arisen for the analysis of the noise produced by hydrodynamic sources and transmitted on board. Among the others the turbulent boundary layer attached to the hull of the vessel is recognised to be one of the most important. The random travelling pressure field associated to the turbulent boundary layer induces high frequency vibrations of the hull's elastic parts that radiate noise on board the vessel. Thus the problem of the characterisation of the pressure field is similar to that related to noise transmission in the aeroplane fuselages but, due to presence of the free water surface, depends on the Froude number as well as on the Reynolds number. An experimental campaign was carried out on a model of a fast ship in a towing tank to investigate the problem. Laser doppler velocimetry and numerical simulations are used to evaluate the mean flow velocity parameters. An array of pressure transducers located along the hull to separate the effects due to Re and to Fr are used to measure the pressure fluctuations. The statistical characteristics of the pressure spectra are obtained from the analysis of the experimental data and the validity of different scaling laws is investigated.