Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, WITS, 2050 Johannesburg, South Africa.
Centre de Recherche en Paléontologie-Paris, UMR 7207 CNRS-MNHN-SU, Muséum national d'Histoire naturelle, CP38, 8 rue Buffon, 75005 Paris, France.
Bioinspir Biomim. 2024 Jan 30;19(2). doi: 10.1088/1748-3190/ad1dbb.
The agamid lizards of the genusare undoubtedly the most renown reptilian gliders, using their rib-supported patagial wings as lifting surfaces while airborne. Recent investigations into these reptiles highlighted the role of body posture during gliding, however, the aerodynamics of postural changes inremain unclear. Here, we examine the aerodynamics and gliding performances ofusing a numerical approach focusing on three postural changes: wing expansion, body camber, and limb positioning. To this aim, we conducted 70 three-dimensional steady-state computational fluid dynamics simulations of gliding flight and 240 two-dimensional glide trajectory calculations. Our results demonstrate that while airborne,generates a separated turbulent boundary layer over its wings characterized by a large recirculation cell that is kept attached to the wing surface by interaction with wing-tip vortices, increasing lift generation. This lift generating mechanism may be controlled by changing wing expansion and shape to modulate the generation of aerodynamic force. Furthermore, our trajectory simulations highlight the influence of body camber and orientation on glide range. This sheds light on howcontrols its gliding performance, and conforms to the observation that these animals plan their glide paths prior to take off. Lastly,is mostly neutral in pitch and highly maneuverable, similar to other vertebrate gliders. The numerical study presented here thus provides a better understanding of the lift generating mechanism and the influence of postural changes in flight in this emblematic animal and will facilitate the study of gliding flight in analogous gliding reptiles for which direct observations are unavailable.
无疑，蜥蜴属的蜥蜴是最著名的滑翔爬行动物，它们利用肋骨支撑的翼膜作为升力面在空中飞行。最近对这些爬行动物的研究强调了滑翔过程中身体姿势的作用，但关于姿势变化的空气动力学仍不清楚。在这里，我们使用数值方法研究了蜥蜴的空气动力学和滑翔性能，重点研究了三种姿势变化：翼展、体弯度和肢体位置。为此，我们进行了 70 次三维稳态计算流体动力学滑翔飞行模拟和 240 次二维滑翔轨迹计算。我们的结果表明，在空中时，蜥蜴会在其翅膀上产生一个分离的湍流边界层，其特征是一个大的回流区，通过与翼尖涡的相互作用，保持附着在机翼表面，从而增加升力的产生。这种产生升力的机制可以通过改变翅膀的扩张和形状来控制，从而调节空气动力的产生。此外，我们的轨迹模拟突出了体弯度和方向对滑翔范围的影响。这揭示了蜥蜴如何控制其滑翔性能，并且符合这样的观察，即这些动物在起飞前就规划了它们的滑翔路径。最后，蜥蜴在俯仰方向上基本是中性的，并且具有很高的机动性，类似于其他脊椎动物滑翔者。因此，这里提出的数值研究提供了对这种有代表性动物的升力产生机制和飞行中姿势变化影响的更好理解，并将有助于研究那些没有直接观测的类似滑翔爬行动物的滑翔飞行。
