An experimental study to characterize the effect of winglet-like geometries on the performance of UAV propellers

Blade tip geometries strongly influence the aerodynamic performance of small Unmanned Aerial Vehicle (UAV) propellers operating at low Reynolds numbers (Re), where tip-vortex-induced losses become significant. Inspired by the effectiveness of winglets on fixed-wing aircraft, this study experimentally investigates the aerodynamic impact of winglet-like tip geometries applied to UAV propellers. Seven configurations were tested, including a baseline propeller and propellers equipped with upward- and downward-facing winglets of varying heights (4–8 mm). Static thrust and torque measurements were conducted over a rotational speed range of 2000 to 5500 RPM, and performance was evaluated using nondimensional coefficients and figure of merit. In addition, 2D Particle Image Velocimetry (PIV) measurements were employed to characterize near-wake flow behavior. The results show that a 4 mm upward-facing winglet produced an approximately 3% increase in thrust relative to the baseline propeller while maintaining comparable efficiency. PIV measurements indicate that this configuration weakened the tip vortex, reduced near-wake vorticity, and decreased the turbulent kinetic energy. In contrast, larger or downward-facing winglets introduced additional flow losses and degraded performance. The observed performance trends highlight the inherently nonlinear aerodynamic response of low -Re propellers, where small geometric modifications such as winglet-inspired tip geometries lead to non-proportional changes in thrust, efficiency, and wake dynamics.