Biomimetically Inspired Design of a Low-Noise Pump-Jet Impeller Based on Hydrodynamic–Acoustic Coupling Analysis

Pump-jet propulsion technology is increasingly applied in uncrewed underwater vehicle propulsion. A key research focus is the biomimetic design of pump-jets to improve efficiency and reduce noise. However, accurately evaluating the impact of such designs is challenging due to the lack of effective numerical methods that capture the interaction between complex internal flows and acoustic propagation. A hydrodynamic–acoustic coupling method based on vortex sound theory is established in this study for pump-jet propulsor design, and the method is validated with the results of a water tunnel experiment. Inspired by the serrated trailing edges of owl wings, each rotor blade has a bionic serrated structure. The serration geometry is optimized using a response surface methodology, with objectives including improved hydraulic efficiency and reduced noise. Results show that the most efficient point of the optimized model is increased by 1.5% compared to the original model, and its location is close to the design condition. The serrated structure reduces pressure gradients and suppresses tip backflow, delays flow separation, and weakens large-scale vortices. The modified trailing edge reduces the noise amplitude without altering spectral characteristics, and the total sound pressure level is reduced by 2.3–5.1 dB. Among the serration parameters, spacing has the greatest effect on efficiency, while height most strongly influences noise suppression.