Wang Shizhao, Zhang Xing, He Guowei, Liu Tianshu
The State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
The State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
J R Soc Interface. 2015 Dec 6;12(113):20150821. doi: 10.1098/rsif.2015.0821.
This paper elucidates the aerodynamic role of the dynamically changing wingspan in bat flight. Based on direct numerical simulations of the flow over a slow-flying bat, it is found that the dynamically changing wingspan can significantly enhance the lift. Further, an analysis of flow structures and lift decomposition reveal that the elevated vortex lift associated with the leading-edge vortices intensified by the dynamically changing wingspan considerably contributed to enhancement of the time-averaged lift. The nonlinear interaction between the dynamically changing wing and the vortical structures plays an important role in the lift enhancement of a flying bat in addition to the geometrical effect of changing the lifting-surface area in a flapping cycle. In addition, the dynamically changing wingspan leads to the higher efficiency in terms of generating lift for a given amount of the mechanical energy consumed in flight.
本文阐明了动态变化的翼展在蝙蝠飞行中的空气动力学作用。基于对慢速飞行蝙蝠周围气流的直接数值模拟，发现动态变化的翼展能显著增强升力。此外，对流动结构和升力分解的分析表明，与动态变化的翼展强化的前缘涡相关的增强涡升力对时间平均升力的增强有很大贡献。除了在拍打周期中改变升力面面积的几何效应外，动态变化的翅膀与涡结构之间的非线性相互作用在飞行蝙蝠的升力增强中也起着重要作用。此外，对于飞行中消耗的给定机械能，动态变化的翼展在产生升力方面具有更高的效率。
