Effect of wing morphing on stability and energy harvesting in albatross dynamic soaring

Abstract

Dynamic soaring, which harvests energy from the wind, can enhance Unmanned Aerial Vehicles’ (UAVs’) range and endurance. However, energy harvesting efficiency issues hinder UAV applications, which can be addressed by wing morphing. Therefore, this study investigates the influence of albatross wing morphing during dynamic soaring. By constructing a parametric model, the shape of the albatross wing can be modeled and achieve morphing based on joints. From the video data, this paper summarizes the typical wing morphing patterns of the albatross and notices that changes primarily occur during the leeward descent phase. This paper first analyzes the aerodynamic performance of different wing morphing patterns and finds that the drag coefficient can be reduced by 7.75% with a suitable morphing pattern. This paper also explores the drag coefficient reduction mechanism and finds that downwash airflow decreases by 30.32% after wingtip anhedral. Interestingly, the lift-to-drag ratio shows minimal variation under different morphing patterns, within 2%. From the stability perspective, this study finds that the neutral point position changes after morphing. The maximum longitudinal static margin change is 4.9%, enhancing longitudinal stability by increasing the restorative moment arm. The lateral neutral point is 4.87% closer to the center of gravity, decreasing the roll and yaw moments. It can be observed that wingtip anhedral significantly increases the stability of the albatross. Moreover, a flight simulation is carried out to study the morphing influence on trajectory and energy harvesting. The results show that maximum energy gained is improved by 47.99%, and endurance is increased by 13.05%. The results also indicate that the effects of wing morphing are global rather than limited to the phase of morphing occurrence. Finally, based on the results, this paper proposes wing morphing regularity about the wingtip for UAVs. Wingtip bends downward can significantly increase the UAVs’ stability and reduce drag, but the overall trajectory needs to be reconsidered after introducing wing morphing.