Three Dimensional Analysis for Self-Propelled Fish Models with Various Shapes near Water Surface

Abstract

Although numerous studies for fish swimming have been reported, there are many problems or mysteries that remain unsolved, for example, high propulsive efficiency of actual living fishes compared with fish robots, and the aim or advantages of fish jumping through water surface. In order to discuss influence of fish shape and swimming depth on its swimming velocity near the water surface, flow around self-propelled fish models with various shapes is analyzed numerically by using the level set method and the modified body-force type immersed boundary method. The swimming velocity of the fish was greatly changed by a ratio of the projected area in the propulsive direction to the projected area in the moving direction of the tail fin. Among various shape models that the ratio is constant, the smaller the projected area in the propulsive direction became, the higher the terminal swimming velocity became. This result did not depend on the swimming depth.