Torsional Vibrations in Ship’s Propulsion Device Accounting for Parametric Excitation and Propeller-Engine Coupling

A new model to analyse torsional vibration problems in ships is proposed. The model accounts for the time dependent inertial properties of the crankshaft mechanism and for the effects related to the vibration induced by the propeller rotating in a non-uniform flow. Main design restraints between characteristic parameters are involved leading to a set of prototype dimensionless equations solved in numerical form. A comparison between the solution obtained by the proposed model and the one given by the traditional equivalent flywheel method is performed. Some characteristic maps of the propulsion system are determined providing the analyst with a convenient tool to correct the torsional stress prediction based on a conventional method.