Ressaut hydraulique ondulé : mythes et réalités

Undular hydraulic jump: myths and reality

Maître de conférences en Hydraulique et Mécaniques des Fluides, Department of Civil Engineering, The University of Queensland, Brisbane QLD 4072, Australie

Abstract

In open channels, the transition from supercritical to subcritical fiows is called a hydraulic jump. For low upstream Froude numbers, free-surfaee undulations develop downstream of the jump. Such a 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. The experimental data include free-surface profiles, velocity distributions, pressure distributions and local head profiles upstream and downstream of undular jumps. Visual and photographic observations indicate five types of undular jumps. For Fr > 1.2, the first wave crest is characterised by the development of Lateral shock waves. The analysis of the data shows that the jump characteristics (e.g. wave length, wave amplitude) are functions of the upstream Froude number and the blockage ratio d_c /W. The disappearance of the undular jump is observed for Froude numbers ranging from 1.5 to 2.9.