Computational and experimental study on dynamics behavior of a bionic underwater robot with multi-flexible caudal fins

Abstract

Purpose This paper aims to develop a novel type of bionic underwater robot (BUR) with multi-flexible caudal fins. With the coordinate movement of multi-caudal fins, BUR will combine the undulation propulsion mode of carangiform fish and jet propulsion mode of jellyfish together organically. The use of Computational Fluid Dynamics (CFD) and experimental method helps to reveal the effect of caudal fin stiffness and motion parameters on its hydrodynamic forces. Design/methodology/approach First, the prototype of BUR was given by mimicking the shape and propulsion mechanism of both carangiform fish and jellyfish. Besides, the kinematics models in both undulation and jet propulsion modes were established. Then, the effects of caudal fin stiffness on its hydrodynamic forces were investigated based on the CFD method. Finally, an experimental set-up was developed to test and verify the effects of the caudal fin stiffness on its hydrodynamic forces under different caudal fin actuation frequency and amplitude. Findings The results of this paper demonstrate that BUR with multi-flexible caudal fins combines the hydrodynamic characteristics of undulation and jet propulsion modes. In addition, the caudal fin with medium stiffness can generate larger thrust force and reduce the reactive power. Practical implications This paper implies that robotic fish can be equipped with both undulation and jet propulsion modes to optimize the swimming performance in the future. Originality/value This paper provides a BUR with multi-propulsion modes, which has the merits of high propulsion efficiency, high acceleration performance and overcome the head shaken problem effectively.

Tail-stiffness optimization for a flexible robotic fish

“…Cui and Jiang [17] established a model of a robotic fish driven by a single joint and connected to several passive joints, and proved that swimming performance could be optimized by varying the stiffness. In the study by Xie et al [18], the performance of a caudal fin with medium stiffness was the best, and a similar conclusion was reached in [19]. In [20], the stiffness of the robotic fish was adjusted by varying the air pressure on the fish body so that the natural frequency could range from 2.0 to 2.8 Hz.…”

“…Compared with a rigid fin, a robotic fish propelled by a flexible caudal fin can perform the undulation curve of natural fish better. However, the kinematics and control of a fully flexible fin are more complex [18,20], and changing the stiffness requires making a new tail. Several studies have used passive flexible joints to connect rigid fins to realize propulsion [23,24].…”

The Role of Double-Tentacled Cooperative Kinematics on the Hydrodynamics of a Self-propelled Swimmer

“…Their systematic experiments confirmed that a reasonable swing law can realize complex movements, such as ascending and turning (Zhang et al 2016;Liao et al 2018). Xie et al (2018) proposed a four-tailed bionic jellyfish robot, which organically combined wave and jet propulsions, thus revealing the influence of a new propulsion concept on hydrodynamics. Coelho et al (2020) studied the propagation law of interface of active nematics on substrates based on microhydrodynamics, revealing the impact of the second flagellum on the bacteria motility.…”

Structural design and mechanism verification of multi-tailed collaborative robotic fish

“…Zhao et al [15], [16] built a hydrodynamic model for the double tail fin robotic. Through CFD simulation and experiments, Xie et al [17] verified the large thrust peak generated by octopus multi-arm swimming and the larger average thrust in fish swing mode. Previous studies on multi caudal fins mainly focused on the flexible tail fin and multi degree of freedom rigid tail fin, and the exploration of the single degree of freedom multi joint caudal is rarely reported.…”