Author(s)

A. S. VAGHEFI & M. ABBASPOUR

Abstract

Experimental hydrodynamics imaging of four Pangasius sanitwongsei were considered. A quantitative characterization of caudal fin is presented in this article. Steady swimming of four P. sanitwongsei with different total length was studied experimentally and taped by high-speed digital video, and undulatory movement of each fish at different velocity was revealed. The pattern of body undulatory movement of the fish was drawn from the video images. Three main factors that determine the fish swimming behavior are Reynolds number, Strouhal number and shape. In this study, Lf/L was chosen as a characteristic of shape, where Lf was the distance from the start of the head to the end of the head. This is a major point and displays less variation of head to the more variation of the body and caudal fin. L is the length of the fish body. The relationship between Reynolds number and Strouhal number of four P. sanitwongsei with different Lf/L were studied here. Then, the relationship between effective non-dimensional parameters in thrust force and kinematic parameters was found. As a result, an experimental equation was formulated. 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, there was an increase in displacement and thrust force also. Then, undulatory movement equation of fish swimming was calculated by fitting a second-order function that describes wave amplitude of this type of fish. All the finding in these researches could be applied to design a robotic fish.

Keywords

Movement equation, fish swimming, robot fish, video image, Pangasius, undulatory