Numerical analysis on flow noise and structure-borne noise of fully appended SUBOFF propelled by a pump-jet

Abstract

This study presents the characteristics of the flow noise of a fully appended SUBOFF propelled by a pump-jet and the comparison with the structure-borne noise. Firstly, the numerical approaches of computational fluid dynamics (CFD) employed to predict the pulsation pressure and the boundary element method (BEM) employed to calculate the flow noise are verified. Then, the pulsation pressure on the pump-jet and the submarine are obtained by the verified CFD model, which is transferred to obtain the flow noise. Finally, the structure-borne noise of coupled pump-jet – shafting – SUBOFF system under distributed pulsation pressure is predicted by coupled finite element method (FEM) and BEM. The spectrum characteristics of the flow noise are similar to those of the pulsation pressure, with peaks at BPF and its multiples. In the studied frequency range, the spectrum characteristics of the structure-borne noise of the submarine are mainly contributed by the longitudinal mode of the shafting system, in-phase mode of the rotor blades, and the characteristic peaks of the pulsation pressure. For the calculation conditions of low-speed navigation, the sound pressure level (SPL) of the structure-borne noise is higher than that of the flow noise. In addition, the structure-borne noise under distributed pulsation pressure is mainly radiated from the conical end caps and the stern, while the flow noise is mainly radiated from the cylindrical hull.