School of Mechanical Engineering and Automation, Beihang University, Beijing 100083, People's Republic of China. Shenyuan Honors College, Beihang University, Beijing 100083, People's Republic of China.
Bioinspir Biomim. 2020 Mar 31;15(3):036014. doi: 10.1088/1748-3190/ab784b.
The amazing multi-modal locomotion of flying squid helps to achieve fast-speed migration and predator-escape behavior. Observation of flying squid has been rarely reported in recent years, since it is challenging to clearly record the flying squid's aquatic-aerial locomotion in a marine environment. The existing reports of squid-flying events are rare and merely record the in-air motion. Therefore, the water-air locomotor transition of flying squid is still unknown. This paper proposes the idea of using CFD to simulate the process of the flying squid (Sthenoteuthis oualaniensis (S. oualaniensis)) launching from water into air. The results for the first time reveal the flow field information of squid in launching phase and show the kinematic parameters of flying squid in quantification. Both a trailing jet and pinch-off vortex rings are formed to generate launching thrust, and the formation number L /D is 5.22, demonstrating that the jet strategy is to produce greater time-averaged thrust rather than higher propulsion efficiency. The results also indicate that the maximum flying speed negatively correlates with the launch angle, indicating that a lower launch angle could result in a larger flying speed for the flying squid to escape. These findings explore the multi-modal locomotion of flying squid from a new perspective, helping to explain the trade-off strategy of water-to-air transition, and further enhance the performance of aquatic-aerial vehicles.
飞鱿鱼令人惊叹的多模态运动有助于实现快速迁移和逃避捕食者的行为。近年来，由于在海洋环境中清晰记录飞鱿鱼的水空运动极具挑战性，因此对飞鱿鱼的观察鲜有报道。现有的鱿鱼飞行事件报告很少，仅仅记录了在空中的运动。因此，飞鱿鱼的水空运动转换仍然未知。本文提出了使用 CFD 模拟飞鱿鱼（Sthenoteuthis oualaniensis (S. oualaniensis)）从水中发射到空气中的过程的想法。结果首次揭示了鱿鱼发射阶段的流场信息，并以定量的方式展示了飞鱿鱼的运动学参数。形成了尾流射流和截流涡旋环来产生发射推力，形成数 L / D 为 5.22，表明射流策略是产生更大的时均推力，而不是更高的推进效率。结果还表明，最大飞行速度与发射角度呈负相关，这表明较低的发射角度可以使飞鱿鱼获得更大的飞行速度以逃脱。这些发现从新的角度探索了飞鱿鱼的多模态运动，有助于解释水空转换的权衡策略，并进一步提高水空两用车辆的性能。
