Quieter Quadcopter Propellers: Aerodynamic and Acoustic Trade-Offs of Toroidal Designs

This study analyses the aerodynamic and acoustic trade-offs of toroidal quadcopter propellers using variants derived from the APC 10×5 design to guide mission-specific adoption in next-generation quadcopters. Three configurations, namely a two-loop elliptical, a two-loop circular, and a three-loop circular design, were evaluated through CFD simulations. Static thrust tests on a thrust stand validated the CFD model, complementing wind-tunnel validation against published APC 10×5 data. Acoustic assessments used the Ffowcs Williams–Hawkings (FW-H) analogy. The results show that toroidal propellers achieve 38.8 to 59.2 % higher static thrust and significant noise reductions relative to the conventional benchmark, although efficiency is compromised by increased induced drag from vortex diffusion. Specifically, the three-loop circular variant reduced the peak tonal sound pressure level by approximately 26.8 dB (a factor of ≈22 in sound pressure) within the human-sensitive range, yet it suffered a ≈41 % lower thrust-to-weight ratio. The two-loop elliptical variant offered a practical balance with 38.8 % higher static thrust, a peak-tone reduction of ≈2.7 dB, and a maximum propulsive efficiency of 0.57 (vs. 0.69 for the benchmark). Propeller choice therefore dictates mission suitability: three-loop designs best serve noise-sensitive tasks such as surveillance, while elliptical designs better serve infrastructure inspection missions requiring a balance of efficiency and thrust.