Aerodynamic Performance Enhancement of Small Fixed-Wing Unmanned Aerial Vehicles through Bio-Inspired Microfiber Surfaces

This work focuses on the application of an innovative passive flow control technique, utilizing microfiber coatings with diverging pillar cross-sections, inspired by gecko feet, on the wing of a small unmanned aerial vehicle (UAV). The starting point in the study was the development of a small-scale modular UAV to explore the concept of reconfigurability. In this process, a multidisciplinary approach was taken, integrating computational fluid dynamics (CFD), structural analysis of 3-D printed structures, and wind tunnel testing for validation. This UAV demonstrated versatility across different mission profiles, with low-speed and high-speed variants optimized for endurance and time-critical missions. Later, the same UAV model was used as a test apparatus for the bio-inspired microfiber research. Wind tunnel experiments in static and dynamic conditions were conducted to evaluate the coatings' effects on aerodynamic performance and control surface authority. In static tests, the microfiber pillars significantly reduced drag, with up to a 24.7$\%$ reduction at the cruise Reynolds number. Control surface effectiveness, particularly in pitching moments, saw marked improvement, especially near stall conditions, with an increase in control authority of up to 22.4$\%$. Dynamic tests revealed enhanced damping characteristics at low angles of attack, which translates into higher maneuverability in terms of normal acceleration production per control surface input. By combining the novel microfiber flow control approach with reconfigurable UAV design, this work highlights potential advancements in UAV performance, advocating for further research in both areas to optimize aerodynamics and structural integrity for diverse operational requirements.