ABSTRACT Flow around a fish is investigated by solving Navier-Stokes equations and continuity equation numerically. The two dimensional wing which moves like a fish is considered as the simplest model. The motion has a transverse wave progressing along the body from head to tall and the amplitude of the wave increases from zero at the head to a maximum at the tail. Lammar flow field is solved for simplicity. The equation is discretized by first -order backward difference for time and 5-point finite analytic method of Chen and Patel for space The pressure-velocity coupling is accomplished by SIMPLER algorithm. The moving body fitted grid system is used for moving body and the grid is generated at each time step. The computational results show very complicated vortical wake and flow field around wing. The axial and lateral forces are also presented and discussed. The results for some other pattern movement show the essential feature of the fish like motion.
INTRODUCTION The flow field around a swimming fish or a aquatic mammal has been investigated for a long time by the researchers in various field of study such as biology, physical science and engineering experimentally (The rowel paper of Narasako(1985). This interest has been inspired not only to understand and Simulate efficient swimming propulsion, but also to utilize the results for engineering application In the field of theoretical hydrodynamics, numerous studies on two and three dimensional flow around fish-like body have been done since the slender-fish theory of Lighthill(1960) and two dimensional unsteady lifting surface theory of Wu(1961) and have contributed to the present understanding of the hydro dynamical and biological aspects of swimming Typical studies, Citing example references, are as follows Lighthill(1970). Wu(J.971) and Karpouzian et al.(1990) studied theoretically mainly by means of ideal fluid model Chopra(1976) showed the unsteady lifting surface methods incorporating distributed singularities Vortex-lattice and panel methods have been used by Lan(1979) and Cheng et al (1991).