Numerical study of complex modal characteristics in anguilliform mode of fish swimming

Autor: Hongzhou Jiang, Zuo Cui
Rok vydání: 2021
Předmět:
Zdroj: Journal of Mechanical Science and Technology. 35:4511-4521
ISSN: 1976-3824
1738-494X
Popis: In nature, anguilliform fish swim fast and efficiently by undulating their elongate body in a specific way, which is generally described as a travelling wave. In present work, the undulatory motions of anguilliform fish are analyzed by the method of complex orthogonal decomposition (COD), and these particular motions are decomposed into two parts: the travelling component and standing component. The relative ratio between the travelling and standing components is defined as the travelling index, and the biological data show that anguilliform fish prefer to the undulatory motions with high travelling index (0.74–0.90). To study this phenomenon, a two-dimensional numerical model of anguilliform fish is developed by our proposed LS-IB numerical method, in which the shape of fish body is described by level-set (LS) function, and the interactive force is demonstrated by the immersed boundary (IB) method. The results show that the net force is decreased slightly with the travelling index, but the efficiency is increased with the travelling index until it reached to 0.8, which is consistent with the biological observations. Besides, the influences of the oscillating amplitude, tail-beat frequency and Strouhal number are also discussed. Overall, the results in present study can be used to explain why anguilliform fish would like to select the swimming gaits with high travelling index.
Databáze: OpenAIRE
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