Stevenson Jonathan P J, Cheney Jorn A, Usherwood James R, Bomphrey Richard J, Windsor Shane P
Department of Aerospace Engineering, University of Bristol, Bristol BS8 1TR, UK.
Structure and Motion Laboratory, Royal Veterinary College, Hatfield AL9 7TA, UK.
R Soc Open Sci. 2023 May 10;10(5):221607. doi: 10.1098/rsos.221607. eCollection 2023 May.
A bird's wings are articulated to its body via highly mobile shoulder joints. The joints confer an impressive range of motion, enabling the wings to make broad, sweeping movements that can modulate quite dramatically the production of aerodynamic load. This is enormously useful in challenging flight environments, especially the gusty, turbulent layers of the lower atmosphere. In this study, we develop a dynamics model to examine how a bird-scale gliding aircraft can use wing-root hinges (analogous to avian shoulder joints) to reject the initial impact of a strong upward gust. The idea requires that the spanwise centre of pressure and the centre of percussion of the hinged wing start, and stay, in good initial alignment (the centre of percussion here is related to the idea of a 'sweet spot' on a bat, as in cricket or baseball). We propose a method for achieving this rejection passively, for which the essential ingredients are (i) appropriate lift and mass distributions; (ii) hinges under constant initial torque; and (iii) a wing whose sections stall softly. When configured correctly, the gusted wings will first pivot on their hinges without disturbing the fuselage of the aircraft, affording time for other corrective actions to engage. We expect this system to enhance the control of aircraft that fly in gusty conditions.
鸟类的翅膀通过高度灵活的肩关节与身体相连。这些关节赋予了令人印象深刻的运动范围，使翅膀能够做出大幅度的挥动动作，从而能显著调节空气动力负载的产生。这在具有挑战性的飞行环境中非常有用，尤其是在低层大气中阵风强烈、气流湍急的区域。在本研究中，我们建立了一个动力学模型，以研究一架鸟类大小的滑翔机如何利用机翼根部的铰链（类似于鸟类的肩关节）来抵御强烈向上阵风的初始冲击。这个想法要求铰接机翼的展向压力中心和撞击中心一开始就保持良好的初始对齐状态（这里的撞击中心与板球或棒球中球棒上的“甜蜜点”概念相关）。我们提出了一种被动实现这种抵御的方法，其关键要素包括：（i）适当的升力和质量分布；（ii）处于恒定初始扭矩下的铰链；（iii）机翼剖面能柔和失速的机翼。当配置正确时，阵风作用下的机翼将首先在其铰链上转动，而不会干扰飞机机身，从而为采取其他纠正措施留出时间。我们期望这个系统能增强在阵风条件下飞行的飞机的操控性。
