Comparative Study of Morphing Winglet Configurations for High-Altitude Long-Endurance Unmanned Aerial Vehicle Applications

Abstract

This paper offers the conceptual design, computational modeling and aerodynamic evaluation of morphing winglet designs in the context of high-altitude long-endurance (HALE) unmanned aerial vehicles (UAVs). The winglet styles investigated in CAD-based modeling and computational fluid dynamics simulations in ANSYS Fluent were (1) a canted blended winglet with a morphing plain flap, (2) a raked winglet with an extended wingtip and plain flap, and (3) a conventional blended winglet with a plain flap. The choice of these configurations was driven by the need to reflect different aerodynamic design philosophies that sought to optimize the performance of a HALE UAV over the different flight regimes that the vehicle undergoes. The canted blended winglet with a morphing plain flap (Configuration 1) was chosen based on its ability to counter induced drag through the reduction of wingtip vortices and the ease with which air passes through the wing and winglet, respectively. The winglet with a long wingtip and bare flap (Configuration 2) was added in order to realize the benefits of a higher effective wingspan, which leads to better spanwise lift distribution and higher lift production at lower speeds. Lastly, the traditional blended winglet with a simple flap (Configuration 3) was chosen as a control model because it possessed long-standing aerodynamic stability and consistent performance. The integrated nature of the wing and winglet reduces interference drag and secures predictable aerodynamic flow behavior during landing and low-speed flight. A combination of the three configurations offers a holistic approach to the assessment of the effects of geometric variations of winglets on the overall aerodynamic efficiency and mission flexibility of HALE UAVs. It was simulated under representative takeoff, cruise, and landing conditions, with variation in the angle of attack, flap deflection, and altitude. The findings reveal configuration-specific aerodynamic benefits: the canted blended winglet (Config-1) achieved the highest lift-to-drag ratio (L/D = 17.81) during cruise, whereas the raked winglet (Config-2) produced the highest lift during takeoff, and the blended winglet (Config-3) performed best during the landing phase. Morphing flap deflections also improved lift generation, postponed stall onset, and minimized flow separation across all flight phases.