Numerical simulation of manta ray's self-propulsion

蝠鲼自主游动数值模拟研究

¹ Air Defence and Antimissile School, Air Force Engineering University, Xi'an 710038, China
² School of Marine Science and Technology, Northwestern Polytechnical University, Xi'an 710072, China

Received: 10 January 2024

Abstract

A manta ray is a typical representation of its pectoral fin propulsion mode, which is stable and conducive to wide area cruise, thus being suitable for bionic targets of a bionic vehicle. This paper established a computational model of the two-degree-of-freedom self-propulsion of the manta ray. Its motion equation and fluid dynamic equation were coupled to numerically simulate its self-propulsion process from stationary-state start-up and acceleration to steady-state cruise. The time history changes of the manta ray's swimming speed, hydrodynamic force, pressure distribution and three-dimensional flow field structure were analyzed. The simulation results show that, during the self-propulsion process of the manta ray, its speed, acceleration and displacement in its forward direction are completely determined by the net thrust generated during the flexible deformation of the pectoral fins and the net resistance encountered during its forward swimming. In the acceleration stage, the net thrust is superior and mainly generated near the tips of the pectoral fins. When the balance between the thrust and the resistance is reached, the manta ray is in its steady cruise stage. The flexible deformation of the spanwise and chordwise superposition of the pectoral fins may produce complex three-dimensional vortex structures. The numerical simulation method proposed in this paper and the study of the manta ray's self-propulsion process lay the foundation for further revealing its swimming mechanisms.

摘要

蝠鲼是胸鳍推进模式的典型代表, 稳定性好, 利于广域巡游, 非常适合作为仿生航行器的仿生目标。建立蝠鲼两自由度自主游动的计算模型, 耦合求解蝠鲼运动方程与流体动力方程, 数值模拟了蝠鲼从静止状态启动加速, 最终到达稳态巡游的自主游动过程, 分析了蝠鲼游动速度、水动力、压力分布以及三维流场结构的时间历程变化。计算结果表明: 在蝠鲼自主游动过程中, 前游方向的速度、加速度、位移等完全由胸鳍柔性变形时产生的净推力以及前游时受到的净阻力共同决定, 在加速阶段净推力占优, 且推力主要由靠近鳍尖部分产生, 推阻力平衡时蝠鲼到达稳态巡游阶段, 蝠鲼胸鳍展向及弦向叠加的柔性变形会产生复杂的三维涡结构。文中提出的数值仿真方法以及对蝠鲼自主游动过程的研究为后续揭示蝠鲼游动机理奠定了基础。