Li Xiaohu
Jiangsu University of Science and Technology, Zhenjiang 212003, China.
Appl Bionics Biomech. 2021 Jan 2;2021:6630839. doi: 10.1155/2021/6630839. eCollection 2021.
Tuna can change the area and shape of the median fins, including the first dorsal, second dorsal, and anal fins. The morphing median fins have the ability of adjusting the hydrodynamic forces, thereby affecting the yaw mobility of tuna to a certain extent. In this paper, the hydrodynamic analysis of the median fins under different morphing states is carried out by the numerical method, so as to clarify the influence of the erected median fins on the yaw maneuvers. By comparing the two morphing states of erected and depressed, it can be concluded that the erected median fins can increase their own hydrodynamic forces during the yaw movement. However, the second dorsal and anal fins have limited influence on the yaw maneuverability, and they tend to maintain the stability of tuna. The first dorsal fin has more lift increment in the erection state, which can obviously affect the hydrodynamic performance of tuna. Moreover, as the median fins are erected, the hydrodynamic forces of the tuna's body increase synchronously due to the interaction between the body and the median fins, which is also very beneficial to the yaw motion. This study indicates that tuna can use the morphing median fins to adjust its mobility and stability, which provides a new idea for the design of robotic fish.
金枪鱼能够改变包括第一背鳍、第二背鳍和臀鳍在内的中央鳍的面积和形状。形态可变的中央鳍具有调节水动力的能力，从而在一定程度上影响金枪鱼的偏航机动性。本文采用数值方法对不同形态状态下的中央鳍进行水动力分析，以阐明竖起的中央鳍对偏航机动的影响。通过比较竖起和压低这两种形态状态，可以得出结论：在偏航运动过程中，竖起的中央鳍能够增加自身的水动力。然而，第二背鳍和臀鳍对偏航机动性的影响有限，它们倾向于维持金枪鱼的稳定性。第一背鳍在竖起状态下有更多的升力增量，这能够显著影响金枪鱼的水动力性能。此外，随着中央鳍竖起，由于鱼体与中央鳍之间的相互作用，金枪鱼身体的水动力会同步增加，这对偏航运动也非常有利。这项研究表明，金枪鱼可以利用形态可变的中央鳍来调节其机动性和稳定性，这为机器鱼的设计提供了新思路。
