Effects of the duct on the vibro-acoustic characteristics of the pump-jet–shaft–submarine system under pump-jet excitation

Abstract

The characteristics of the distributed pressure on duct induced by rotor and its effects on the vibro-acoustic response of the coupled pump-jet – shaft – submarine system are investigated. Firstly, the pulsating pressure on the duct and the rotor of the pump-jet is computed by numerical approaches of computational fluid dynamics (CFD). Then, the pulsating pressures on CFD mesh are mapped to structural mesh based upon radical basis function to apply them on the pump-jet to calculate the vibro-acoustic responses of the coupled pump-jet – shaft – submarine system by coupled finite element method (FEM) and direct boundary element method (BEM). Finally, the effects of the duct (including the distributed pressure on it as well as the vibration transmission characteristics) on sound radiation are investigated. The results show that the distributed pressure on the inner surface of the duct near rotor disk is a kind of traveling wave pressure, which is tonal at blade passing frequency and its harmonics. The main contribution of the unsteady distributed pressure on the duct to the underwater sound radiation mainly reflects at blade passing frequency (BPF), as well as the duct modes and the hull bending modes that exhibit large deformation at the locations for the stator blades attached to.