Journal of Fluid Mechanics



Analysis of swimming three-dimensional waving plates


Jian-Yu  Cheng a1, Li-Xian  Zhuang a1 and Bing-Gang  Tong a1
a1 Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui, China

Article author query
cheng jy   [Google Scholar] 
zhuang lx   [Google Scholar] 
tong bg   [Google Scholar] 
 

Abstract

The three-dimensional waving plate theory is developed to investigate the swimming performance of fish undulatory motion. In particular, the propulsive effectiveness is discussed. The unsteady potential flow over model rectangular and triangular flexible plates performing a motion which consists of a progressing wave with variable amplitudes is calculated by the vortex ring panel method. It is found that the undulatory motion can reduce three-dimensional effects. It is this important hydrodynamic phenomenon that may be one of the main reasons why such undulation is widely used as the swimming method by a large number of aquatic animals. When the span of the undulating plate is nearly unchanged and the wave amplitude is constant or increases slightly along the chord, and the wavelength is close to the body length, theoretical results show that the swimming performance is best and the flow around the plate has a quasi-two-dimensional property. This swimming method may be observed in many fishes, especially those with an anguilliform mode of propulsion. The modification of the anguilliform mode of propulsion to the carangiform mode is also discussed. It is confirmed that the pronounced necking of the body anterior to the tail, which acts to improve the propulsive performance, is a major morphological adaptation of fishes using the carangiform mode, in which the characteristic nature of flexural movement confined to the rear part of the body is that the amplitude of undulation increases posteriorly and no complete wavelength is at any time apparent.

(Published Online April 26 2006)
(Received December 7 1989)
(Revised January 15 1991)



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