Theoretical and numerical studies on a five-ray flexible pectoral fin during labriform swimming

Abstract

Natural fish have evolved with an excellent swimming performance after millions of years. Based on the flexible features of the pectoral fin, this paper focuses on the kinematics and hydrodynamics of the fin when fish are swimming stably in still water in labriform mode. The locomotion mechanism based on the morphology of the pectoral fin is applied to establish a kinematic model composed of five rays and membranes, which is adopted to control the pectoral fin to reach deformation in approximately the same way as the labriform mode. A semi-empirical theoretical model based on the kinematics is proposed to calculate the hydrodynamic force. In order to study the flow field, the numerical simulation of fluid-structure interaction is carried out and the results are validated by the present semi-empirical model, which also verifies the feasibility of the semi-empirical theoretical model for describing the dynamics of the pectoral fin under a complex water environment. In addition, the relationship between propulsion performance and locomotion parameters (e.g. frequency of motion, amplitude of flapping and rowing angle, and phase lag between flapping and rowing) of the multi-degree of freedom flexible pectoral fin is also revealed. It is found that the frequency and amplitude of the flapping angle have a significant influence on the hydrodynamic thrust, while the rowing angle and phase lag have little effect. The established models and the results provide effective tools and significant reference for the design of bionic pectoral fins.

Effects of root chord movement on thrust generation of oscillatory pectoral fins

“…Besides, at a certain f , the same was observed for an increase in A. These findings can demonstrate significant influence of A and f on both thrust and efficiency, which is in agreement with the findings of hydrodynamic thrust in the literature [36]. For Δ, we used one way paired t-tests (see appendix A for more details on the statistical hypothesis test) to test if thrust is improved after adding more constraints to the movement of root chord.…”

Review of Computational Fluid Dynamics Analysis in Biomimetic Applications for Underwater Vehicles

“…Consequently, scientists have been observing and analyzing the swimming and maneuvering techniques of aquatic creatures, dedicating themselves to the development of innovative, biomimetic AUVs. These organisms use their physical structures and aquatic maneuverability for propulsion, producing undulating movements through the coordination of body, pectoral fins [47], and tail movements [48][49][50]. They also manipulate the surrounding water flow.…”

Design and Reality-Based Modeling Optimization of a Flexible Passive Joint Paddle for Swimming Robots

“…Aquatic animals are adept at using passive changes in their body structures to adapt to or enhance their interactions with fluids, generating complex behaviors from simple movement patterns [ 1 , 2 ]. Flexible propellers can guide the fluid towards the preferred axis without much loss [ 3 ], with simple control modes and high mechanical efficiency [ 4 , 5 ]. This has motivated researchers to take a great interest in flexible propellers.…”