Experimental investigation of a biomimetic propeller coupled with owl-inspired leading and trailing edges serrations

In unmanned aerial vehicle (UAV) propulsion systems, the aerodynamic noise generated by high-speed rotating propellers presents critical challenges for both operational stealth and environmental compliance. While biomimetic designs, such as leading-edge (LE) and trailing-edge (TE) serrations, have shown promise in mitigating noise, the synergistic effects and underlying mechanisms of LE-TE coupled serrations remain poorly understood. This study proposes a bio-inspired coupled propeller (BCP) design that integrates both LE and TE serrations, demonstrating its ability to reduce noise and enhance aerodynamic performance compared to single-structure serrated designs. Using a combination of numerical simulations and experimental validation, we show that the single BCP achieves a maximum noise reduction of 3.1 dB under laboratory conditions, along with a 7.9% improvement in thrust efficiency. When implemented on a quad-rotor UAV for outdoor hovering noise measurements, BCP consistently exhibited superior noise mitigation, attaining a reduction of 2.6–3.8 dB across altitudes ranging from 3 to 12 m, outperforming both LE and TE propellers with single-structure serrations. Spectral analysis reveals that the LE-TE serration structure effectively suppresses both tonal noise at blade passing frequencies (BPF), particularly at 1 BPF, and broadband noise, especially in the range above 2 kHz. The optimized flow control in the coupled-structure design results from the complex interactions between the LE and TE serrations, which induce vortex formation, turbulent modulation, and shedding dissipation. These findings offer new insights into passive flow control mechanisms and pave the way for quieter, more efficient UAV propulsion systems, with broader implications for bio-inspired aircraft design.