A novel cylindrical overlap-and-fling mechanism used by sea butterflies
A novel cylindrical overlap-and-fling mechanism used by sea butterflies
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DOI：
10.1242/jeb.221499
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发表时间：
2020-08-01
影响因子：
2.8
通讯作者：
Murphy, David W.
中科院分区：
文献类型：
--
作者：
Karakas, Ferhat;Maas, Amy E.;Murphy, David W.
拍击和抛掷机构是一种经过充分研究的不稳定升力产生机构，广泛被飞行昆虫使用，并且被认为对于以低到中雷诺数 Re 飞行的微小昆虫是必需的。然而，一些水生浮游动物，包括一些翼足类动物（即海蝴蝶）和杂足类动物，在低至中Re游泳时也使用拍击和投掷机制。这些海洋蜗牛具有极其灵活、主动变形、肌肉发达的翅膀，它们相互拍动以产生推进力，并且这些翅膀可以实现昆虫所不具备的新型升力产生机制，因为昆虫的翅膀不太灵活、被动变形。利用高速立体摄影测量和微粒图像测速，我们描述了翼足类物种 Cuvierina atlantica 使用的一种新颖的圆柱形重叠和抛掷机制。在这种机动中，翼足类的翼尖在每个半冲程结束时重叠，依次形成一个向下开口的圆锥体、一个圆柱体和一个向上开口的圆锥体。从向下开口的圆锥体到圆柱体的过渡在后缘处产生向下的射流。类似地，从圆柱体到向上开口的圆锥体的过渡会产生向下流入机翼之间间隙的气流、前缘涡环以及相应的游动速度的急剧增加。这种翼足类动物能够在每次划水过程中执行两次圆柱形重叠和投掷动作，这得益于其细长的身体和高度灵活的翅膀。这里观察到的圆柱形重叠和抛掷机构可能会启发新型软机器人水下航行器的设计，该航行器采用高度灵活的推进器，以利用这种新颖的升力产生技术。
The clap-and-fling mechanism is a well-studied, unsteady lift generation mechanism widely used by flying insects and is considered obligatory for tiny insects flying at low to intermediate Reynolds numbers, Re. However, some aquatic zooplankters including some pteropod (i.e. sea butterfly) and heteropod species swimming at low to intermediate Re also use the clap-and-fling mechanism. These marine snails have extremely flexible, actively deformed, muscular wings which they flap reciprocally to create propulsive force, and these wings may enable novel lift generation mechanisms not available to insects, which have less flexible, passively deformed wings. Using high-speed stereophotogrammetry and micro-particle image velocimetry, we describe a novel cylindrical overlap-and-fling mechanism used by the pteropod species Cuvierina atlantica. In this maneuver, the pteropod's wingtips overlap at the end of each half-stroke to sequentially form a downward-opening cone, a cylinder and an upward-opening cone. The transition from downward-opening cone to cylinder produces a downward-directed jet at the trailing edges. Similarly, the transition from cylinder to upward-opening cone produces downward flow into the gap between the wings, a leading edge vortex ring and a corresponding sharp increase in swimming speed. The ability of this pteropod species to perform the cylindrical overlap-and-fling maneuver twice during each stroke is enabled by its slender body and highly flexible wings. The cylindrical overlap-and-fling mechanism observed here may inspire the design of new soft robotic aquatic vehicles incorporating highly flexible propulsors to take advantage of this novel lift generation technique.