Jumping dynamics of aquatic animals
Jumping dynamics of aquatic animals
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DOI：
10.1098/rsif.2019.0014
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发表时间：
2019-03-01
影响因子：
3.9
通讯作者：
Jung, Sunghwan
中科院分区：
文献类型：
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作者：
Chang, Brian;Myeong, Jihye;Jung, Sunghwan
跳出水面是各种水生和半水生动物表现出来的一种现象。然而，没有共同的基础工作来澄清跳出水面所需的物理限制。在这项研究中，我们阐明了动物跳出水面所需的身体条件。对五个分类类别的100多个跳跃进行了分析。通过平衡动物产生的力量和阻力引起的耗散，我们预计最大跳跃高度H与身体长度成比例，L，H/L类似于L-1/3，类似于Fr-2，其中弗劳德数Fr是惯性与重力的比率。为了识别跳跃状态，简化的实验是通过射击轴对称物体穿过水面进行的。在这里，我们看到了一个转变，其中部分退出尺度为H/L类似于Fr，完全退出尺度为H/L类似于Fr-2。一种受生物启发的机器人拍打机制被设计成模仿冲动跳跃动物的快速运动。当离开水时，机器人携带着大量的液体，称为夹带质量。建立了一个理论模型来预测各种出水体的跳跃高度，该模型表明，夹带流体的质量相对于物体质量限制了最大跳跃高度。我们的结论是，与我们的水下机器人相比，由于缺乏携带的液体，动物可以达到非凡的高度。
Jumping out of water is a phenomenon exhibited by a variety of aquatic and semi-aquatic animals. Yet, there is no common groundwork that clarifies the physical constraints required to jump out of water. In this study, we elucidate the physical conditions required for an animal to jump out of water. More than 100 jumps are analysed over five taxonomic groups. By balancing the power produced by animals with drag-induced dissipation, we expect that maximum jumping height, H, scales with body length, L, as H/L similar to L-1/3 similar to Fr-2, where the Froude number, Fr, is a ratio of inertia to gravity. To identify jumping regimes, simplified experiments are conducted by shooting axisymmetric bodies through the water surface. Here, we see a transition in which partial exits scale as H/L similar to Fr and complete exits scale as H/L similar to Fr-2. A bioinspired robotic flapping mechanism was designed to mimic the fast motion of impulsive jumping animals. When exiting water, the robot carries a large volume of fluid referred to as an entrained mass. A theoretical model is developed to predict the jumping height of various water-exiting bodies, which shows that the mass of the entrained fluid relative to the mass of the body limits the maximum jumping height. We conclude that the lack of entrained fluid allows animals to reach extraordinary heights compared to our water-exiting robots.