Visualization of longitudinal eddies in an open channel flow

Abstract

An open channel flow is three dimensional because of a coherent motion which is originated in a bursting phenomenon or a depth-scale longitudinal eddy. In this paper the three dimensional turbulent structure of these phenomena were investigated by a flow visualization technique. A tracer method was used to visualize a flow in a cross section, a horizontal section and a vertical section. Neutral tracers were illuminated by a laser light sheet which was obtained from a 5 mW He-Ne gas laser. A video camera and a 35 mm still camera were used in a moving shot or a fixed shot, and many attractive pictures were obtained. To visualize a flow in a cross section, a bore scope shown in Fig. l was used with a image intensifier. Based on these results, the three dimensional turbulent structure of an opn channel flow was illustrated.