Author(s)

M. Abbaspour & A. S. Vaghefi

Abstract

This paper presents a quantitative characterization of caudal fin. Steady swimming of Pangasius sanitwongsei was studied experimentally and taped by high speed digital video and undulatory movement of fish was revealed. As a result, an experimental equation was found. This equation indicates that, as much as the ratio of the end part of fish with high undulatory movement (body and caudal fin) to the total length goes up, the ratio of amplitude to the total length increases. Consequently, displacement increases and thrust force increases too. Then undulatory movement equation of fish swimming was calculated by fitting a second order function which describes wave amplitude of this type of fish. All the findings in these researches could be applied to design a robotic fish. Keywords: undulatory movement equation, fish swimming, robotic fish, video image, Pangasius. 1 Introduction For a long time, scientists have marveled at the graceful way in which fish swim, turn and accelerate [1]. In nature, fish are propelled by the undulatory motion of their body and have gained wonderful swimming ability over the thousands of years of evolution. Tuna swim with high speed and high efficiency. Pike accelerate in a flash, and eels can swim skillfully into narrow holes [2]. From a mechanics appearance, their movements raise questions; how good they are as

Keywords

undulatory movement equation, fish swimming, robotic fish, video image, Pangasius.