Numerical investigation of flow-induced noise for a fully appended underwater vehicle

Abstract

Flow-induced noise, as an acoustic phenomenon generated by fluid motion, mainly originates from unsteady pressure fluctuations exerted by turbulent flow on solid surfaces, with the resulting acoustic energy radiating outward through the fluid medium. For underwater vehicles, stealth is one of the most critical performance indicators. As the structural complexity of such vehicles increases, various appendages inevitably alter the local flow field during navigation, thereby intensifying the generation of flow-induced noise. Among these, protruding structures, such as the sail and stern rudders, as well as recessed structures, such as flood holes, are particularly significant contributors to flow-induced noise because of their pronounced effects on flow separation, vortex evolution, and pressure fluctuations. A review of existing domestic and international studies on hydrodynamic noise indicates that systematic investigations into the influence of different appendage geometries on flow-induced noise remain relatively insufficient. Accordingly, this study focuses on the mechanism of flow-induced noise and selects typical protruding structures and recessed structures as research objects. Their effects on flow-induced noise are systematically analyzed, and the relative intensity of flow-induced noise generated by underwater vehicles under different structural configurations is revealed. The results show that the sail fillet, stern rudder configuration, flood-hole shape, flood-hole depth, and flood-hole layout all significantly affect the flow-induced noise. The sail fillet reduces the total sound pressure level (Total SPL) by approximately 10 dB, with local reductions reaching about 15 dB, while flood-hole shape and layout can lead to larger SPL variations. Furthermore, this study provides theoretical and methodological support for the optimization and noise reduction of underwater vehicles.