Vibro-acoustic characteristics of a submarine model excited by excitation forces of pump-jet duct

Abstract

The vibro-acoustic responses of coupled pump-jet-submarine systems excited by fluid excitations on the wall of the duct are numerically investigated. The unsteady excitations are calculated by computational fluid dynamics and the vibration responses for different excitations on the inner and outer walls are contrastively analyzed through establishing a finite element model of the coupled system. Meanwhile, the effect of fluid–structure interaction and the excitation loading methods for the inner flow of duct are considered. The sound radiation characteristics for different excitation sources are predicted through using a boundary element model. The results show that the excitation force spectra of the inner wall have a remarkable discrete peak at blade passing frequency and its multiple, while the excitation force spectra of the outer wall show a broadband characteristic and discrete components appear at blade passing frequency. The modes of hull both dominate the vibro-acoustic responses of the coupled system for different excitation sources of the duct. The transmitted energy for inner excitation forces is significantly greater than that of outer excitation forces, but the sound radiation efficiency is relatively close. The excitations of the duct can transfer to the thrust bearing through stators as well as the hull and cause a coupled vibration between the duct–stator–hull and the shafting system. Besides, the method for applying distributed forces on the inner wall is more reliable.