A Coupled DBE/FE Analysis for the Prediction of Propeller Induced Pressure and Vibration on the Ship Hull

The present paper deals with a methodology for the prediction of propellers excitation and associated ship response. A simple ellipsoidal representation of submerged and floating bodies has been used first to understand how hull pressure distributions are affected by the location and frequency of propeller sources. Then, the analysis of a ship, a twin-screw cruise liner, has been addressed and semi-empirical methods have been used to give a characterization of propellers in terms of acoustic source strength, in the frequency range between I and 50Hz. Both the ellipsoid and the ship have been analyzed as rigid as well as elastic bodies. In the first case a direct-BEM (boundary element method) analysis has been carried out, whereas in the second case a coupled direct-BEM / structural FEM (finite element method) has been conducted taking into account the dynamic response of the structure. It is worth pointing out that the investigated frequencies range was limited to 50Hz by the definition of the adopted FEM mesh and the forthcoming continuation of the study includes the extension to the limit of 80Hz, indicated by the ISO 6954:2000 standards.