Prediction of hydrodynamic noise in ducted propeller using flow field-acoustic field coupled simulation technique based on novel vortex sound theory

Abstract

As one of the primary noise sources of underwater-robots, the hydrodynamic-noise of the ducted-propeller (DP) originates from various unsteady flows in the flow-field. To investigate the coupling-mechanism between the flow-field and the acoustic-field of DP, this paper establishes a three-dimensional flow field-acoustic field coupling numerical calculation model based on the vortex-acoustic equation. It combines simulation and experimental research to investigate the unsteady flow-field of the DP. The mechanism of acoustic-wave generation and the distribution characteristics of the acoustic field are studied, and the DP's propagation law of hydrodynamic-noise is analyzed based on the field-synergy theory. The results show that the DP domain's vortex structure is mainly influenced by the tensile-distortion and Coriolis-force term. However, hydrodynamic-noise generation is closely related to the vortex, turbulent pulsation, and other unstable flows in the flow-field. The radiated noise of the propeller decreases and then increases with the increase of the inlet velocity-coefficient (IVC) and is smallest at the optimal efficiency point (J = 0.6). With the increase of IVC, the synergy of the propeller flow field-acoustic field is enhanced, the energy-loss of acoustic transmission increases, and the far-field radiation noise decreases. This paper provides a theoretical reference for suppressing the hydrodynamic-noise of the DP and acoustic-optimization design of the underwater-robots.