Multi-mode swimming mechanism of a biomimetic robotic fish based on CFD simulation

doi:10.11996/JG.j.2095-302X.2025051105

Abstract

Abstract:

Bionic robotic fish represent an innovative class of underwater vehicles, characterized by their low noise emission, high reliability, and eco-friendliness. This study investigates the swimming mechanisms of a dual-fin-driven robotic fish through numerical simulations of its multi-mode motion capabilities, employing computational fluid dynamics (CFD). Kinematic and dynamic models of the robotic fish were developed, and the spatial motion equations for the undulating fins were formulated. A fluid simulation model was constructed using Fluent software, incorporating a force-motion coupled dynamic mesh simulation algorithm. The simulation results demonstrated that the robotic fish could execute various multi-mode motions, including forward and backward movement, maneuvering turns, and in-place turns, through the coordinated action of its dual undulating fins. The propulsive force was found to be proportional to the square of the wave frequency, while both the swimming speed and turning speed were directly proportional to the wave frequency. At a frequency of 6 Hz, the robotic fish achieved a swimming speed of 1.25 m/s and a steering speed of 3.2 rad/s. These findings validate the design feasibility and multi-mode motion performance of the robotic fish, providing a theoretical foundation and computational support for the optimization and motion control of the physical prototype of the bionic robotic fish.

Key words: undulating fin, bionic robot, computational fluid dynamics, dynamic mesh, motion control

CLC Number:

TP242

XIA Minghai, LUO Zirong, YIN Qian, LU Zhongyue, JIANG Tao. Multi-mode swimming mechanism of a biomimetic robotic fish based on CFD simulation[J]. Journal of Graphics, 2025, 46(5): 1105-1112.

Figures/Tables 14

Fig. 1 Structure of the bionic fish robot ((a) Design scheme; (b) Structure of the bionic undulating fin)

Fig. 2 CFD Simulation model of the robot ((a) Dynamic grid model of the robot; (b) Domain partitioning of the simulation zone)

Table 1 Parameters of the simulation model

参数类型	参数	数值
质量	质量m	17.0 kg
质量	转动惯量J_yy	0.936 kg·m²
波动鳍尺寸	波动鳍长L	0.456 m
	波动鳍高h	0.15 m
	双鳍间距b	0.377 m
	波动频率f	0~6 Hz
	横波波动幅值θ_m	19.8°
机器人尺寸	载体尺寸(长×宽×高)	0.775 m×0.377 m×0.08 m
机器人尺寸	机器人尺寸(长×宽×高)	0.775 m×0.677 m×0.103 m

Fig. 3 Verification of the grid number and calculation step time ((a) Grid number independence verification; (b) Calculation step time independence verification)

Fig. 4 Coordinate system of the robot

Fig. 5 Simulation results of the thrust force ((a) The thrust force changing with time; (b) The mean thrust changing with frequency)

Fig. 6 Velocity contour image of the robot in linear motion mode

Fig. 7 Velocity and displacement of the robot in linear motion mode

Fig. 8 Propulsive velocity of the robot under different frequencies in linear motion mode

Fig. 9 Simulation results of the steering motion ((a) The planar displacement; (b) The velocity in x and z direction)

Fig. 10 Velocity contour of the robot in steering motion

Fig. 11 Yaw angle and angular speed of the robot in rotation motion

Fig. 12 Driven torque and resistance torque of the robot in rotation motion

Fig. 13 Angular speed under different frequencies in rotation mode

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