Abstract
Fish propelled by body and/or caudal fin (BCF) locomotion can achieve high-efficiency and high-speed swimming performance, by changing their body motion to interact with external fluids. This flexural body motion can be prescribed through its curvature profile. This work indicates that when the fish swims with high efficiency, the curvature amplitude reaches a maximum at the caudal peduncle. In the case of high-speed swimming, the curvature amplitude shows three maxima on the entire body length. It is also demonstrated that, when the Reynolds number is in the range of 104–106, the swimming speed, stride length, and Cost of Transport (COT) are all positively correlated with the tail-beat frequency. A sensitivity analysis of curvature amplitude explains which locations change the most when the fish switches from the high-efficiency swimming mode to the high-speed swimming mode. The comparison among three kinds of BCF fish shows that the optimal swimming performance of thunniform fish is almost the same as that of carangiform fish, while it is better not to neglect the reaction force acting on an anguilliform fish. This study provides a reference for curvature control of bionic fish in a future time.
Highlights
The comparison among three kinds of body and/or caudal fin (BCF) fish shows that the optimal swimming performance of thunniform fish is almost the same as that of carangiform fish, while it is better not to neglect the reaction force acting on an anguilliform fish
Triantafyllou et al discovered that the St (St = fA/U, f is the tail-beat frequency, A is the peak-to-peak amplitude of the tail) range of swimming animals with foil-like tails is
The St range of carangiform fish was 0.19–0.30 and that of thunniform fish was 0.255–0.360, both of which can be identified for efficient propulsion
Summary
After hundreds of millions of years of evolution, fish show superiority in highefficiency and high-speed motion, which has attracted the attention of many researchers. The study on bionic fish can lead to a new design of Automatic Underwater Vehicles (AUV). Most fishes use the body and/or caudal fin (BCF) propulsion to generate. These fishes are distinguished into three categories: anguilliform mode, carangiform. REVIEW of 18 mode, and thunniform mode (Figure 1). Accepted: 11 May 2021 modes are the amplitude envelope of the propulsive wave and the wavelength [1,2]. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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