ABSTRACT:

The mechanism of high speed swimming of some aquatic animals such as mackerel, dolphin have not yet been fully explained. Their swimming motion IS called carangiform. The authors have understood such a motion as an oscillating wing propulsion, i.e., a combination of heaving and pitching of a lunate shape wing. In this paper a trial to realize experimentally the high efficient propulsion by an artificial oscillating wing mechanism IS presented.

1. INTRODUCTION

Many aquatic animals swim by the propulsion force generated from their fin movements. Especially, saurel, mackerel, tuna, dolphin and this kind of aquatic animals are mainly using the strong beating of their tails and tall fins. Their speed of cruising is so fast that sometimes It IS called as Gray" s paradox. This type of swimming is called carangiform, and the movement is restricted In the rear one thirds of the body length. In spite of the difference of species, their tall fins have almost similar shape each other, that is, well known lunate type and high aspect ratio wing (AR = (Wing width)-/(wing area)). Figure shows some samples of their tall fins. From the view point of fluid dynamics their beating motion of tall and tall fin can be understood as a combination of having and pitching motion of the wing (tall fin). Figure 2 shows the mechanism of oscillating fin propulsion. In the figure, the tall now heats from right to left respect to the swimming direction, then it gives the tall fin a heaving motion. The tall fin is a wing following the tail" s motion and makes automatically pitching motion, the angle of which is decided by the balance between fluid force and some kind of elastic force of the muscle of the tall.

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