尾鳍柔性变形对仿生机器鱼自主游动性能影响的研究

Effect of Flexibility of Caudal Fin on Self-propelled Swimming of Bionic Robot Fish

基于计算流体力学方法,数值模拟仿生机器鱼3自由度自主游动,比较刚性尾鳍和柔性变形尾鳍的推力、鱼体游动功率消耗和尾鳍前缘处的涡结构。计算结果表明,在相同运动参数下,柔性尾鳍能使机器鱼在加速阶段游得更快,而刚性尾鳍使机器鱼在巡游阶段游得更快;尾鳍柔性变形能降低巡游阶段机器鱼的侧向速度和首摇角速度的波动幅值,有利于航向稳定。游动速度对柔性尾鳍的推力有明显的负面影响,而对刚性尾鳍的推力影响不大。刚性尾鳍适用于机器鱼在较小的尾鳍侧向平移幅值下巡游,而柔性尾鳍适用于机器鱼在较大的侧向平移幅值下巡游。尾鳍的柔性变形会延迟前缘涡的产生和脱落,导致尾鳍在一个游动周期中的某个时间段形成阻力,不利于机器鱼高速巡游。

Based on computational fluid dynamics(CFD) method, swimming of a self-propelled bionic robot fish with 3-DoF was numerically simulated. Swimming performance, thrust of the caudal fin, power consumption of the fish body and leading-edge vortex structure at the caudal fin were compared between the rigid and the flexible caudal fin. The results show that under the same motion parameters, flexible deformation of the caudal fin makes the robot fish swim faster in the acceleration stage, while the rigid caudal fin makes it swimming faster in the cruise stage. Flexible deformation of the caudal fin can reduce fluctuation amplitude of lateral velocity and yaw angular velocity in the cruising stage, which is beneficial to stable swim of the robot fish in a fixed direction. Swimming speed has a negative effect on the flexible caudal fin, but only little effect on the rigid caudal fin. The rigid caudal fin is suitable for robot fish swimming with small lateral translation amplitude of the caudal fin, while the flexible caudal fin is suitable for robot fish swimming with large lateral translation amplitude of the caudal fin. Flexible deformation of the caudal fin can delay the generation and shedding of leading-edge vortexes, so as to result in resistance of the caudal fin in some time duration in one swimming period, which is not conducive to high-speed cruising of the robot fish.