Prediction of the noise level generated by the turbulent boundary layer on board a fast ship

Recent studies have demonstrated that wall pressure fluctuations generated by the turbulent boundary layer (TBL) on a ship hull can be an important noise source for new generation of high speed vessels. In view to evaluate the noise radiated by elastic ship elements excited by the TBL, an experimental and theorethical procedure has been developed to characterise the hydrodynamic pressure load and the response of an hull plate. In particular, using the results of different experimental campaigns performed in a towing tank on different ship models a complete procedure for the characterisation of the hydrodynamic load is described. Moreover the effects of the free water surface on pressure spectra is discussed. Since the hydrodynamic load is here modeled on the basis of universal scaling laws, this procedure can be applied to derive real size spectra once few information on the full-scale TBL velocity parameters are available. The response of an elastic plate inserted in the catamaran hull model is evaluated experimentally and compared with the prediction of simplyfied closed form expression. Finally the vibro-acoustic response of an elastic structure representative of a ship panel is calculated using the estimated full scale pressure load and the effect of ship velocity variation on the radiated acoustic power is investigated.