Emerging Obstacles in Supercritical Open-Channel Flows: Detached Hydraulic Jump versus Wall-Jet-Like Bow Wave

Abstract

A supercritical open-channel flow can skirt an emerged obstacle by using two distinct forms of workaround: a detached hydraulic jump or a so-called wall-jet-like bow wave. These two forms stem from the properties of supercritical flow and are described in detail. Experiments assess the conditions of appearance of one form or the other, depending on both upstream Froude number and flow-depth to obstacle-width ratio. A conceptual model, based on mass conservation, reproduces and explains the corresponding transition. For the wall-jet-like bow wave, additional information is given regarding water-depth oscillations; the associated Strouhal number show they are caused by reverse spillage on the obstacle face. Implications of the present results on scouring and forces exerted by the flow on structures justify future works on the subject.