Characteristics of Undular Hydraulic Jumps: Experimental Apparatus and Flow Patterns

Abstract

In open channels, the transition from supercritical to subcritical flows is called a hydraulic jump. For low upstream Froude numbers, free-surface undulations develop downstream of the jump and the hydraulic jump is called an undular jump. New experiments on undular hydraulic jumps were performed in a rectangular channel in which the upstream flows were fully developed turbulent shear flows. In this paper, the main flow patterns are described. Visual and photographic observations indicate five types of undular jumps. One of the main flow characteristics is the presence of lateral shock waves for Froude numbers larger than 1.2. The results show that the disappearance of undular jump occurs for Froude numbers ranging from 1.5 to 2.9, and the wavelength and amplitude of free-surface undulations are functions of the upstream Froude number and the aspect ratio y c /W.