Vibration And Sound Radiation Analysis Of Propeller-shaft-hull Coupled System In A SWATH Ship

Vibration and noise radiation level is a key design parameter for surface vessels.The unsteady broadband propeller exciting force transmits to the hull through propulsion shaft system and induces vibration and sound radiation of the hull which is a main low-frequency noise source for surface vessels.Duo to the elasticity of the propeller and propulsion shaft,the propeller exciting force will be magnified during the transmission to the hull.To investigate the “propeller-shaft-hull” coupling vibration and acoustic radiation under low-frequency broadband propeller force,the “propeller-shaft-hull” coupling dynamic model is built with frequency response function based synthesis method.In this model,the elasticity of the propeller is taken in to consideration.The coupled FEM/BEM method and half mode reduction technology are utilized to analyze the vibro-acoustic properties of the propeller and the propulsion shafting.The ship-water coupled model is established with coupled FEM method to investigate the characteristics of the ship.The three-dimensional broadband propeller force is studied.Frequency response function based synthesis method is utilized to formulate the forced responses.Then,the acoustic response is calculated with boundary element method.The proposed method can take into consideration the elasticity of the propeller,the coupling effect of the propeller-shaft and the hull.Vibration transmission path and acoustic radiation characteristics of the coupled system are studied through power flow and force transmission.Analysis results show that the characteristic frequencies of sound radiation power are mainly concentrated on parameters of the shaft and propeller.Therefore,the optimization designs on reducing acoustic radiation are mainly concentrated on parameters of the shaft and propeller.Meanwhile,the proposed method has high efficiency and advantages in terms of parameter analysis for shaft and propeller in a propeller-shaft-hull coupled system,which is of great significance in practical engineering.The influence of propeller,thrust bearing,stern bearing and structure of the foundation are discussed.The corresponding passive control methods are put forward and discussed.