Hydraulic Structures and Society: Engineering Challenges and Extremes ISBN 9781742721156- DOI: 10.14264/uql.2014.15 Turbulent Fluctuations in Hydraulic Jumps: a Physical Study

Abstract: In an open channel, the transformation from a supercritical flow into a subcritical flow is a rapidly varied flow with large turbulent fluctuations, intense air entrainment and substantial energy dissipation: i.e., a hydraulic jump. New experiments were conducted for a wide range of Froude numbers (3.8 < Fr1 < 8.5) at relatively large Reynolds numbers (2.1×104 < Re < 1.6×105) to quantify the turbulent fluctuations. The time-averaged free-surface profile presented some self-similar profile. The longitudinal movements of the jump were observed and both fast and very slow fluctuations were documented for all Froude numbers. The air-water flow measurements quantified the intense aeration of the roller. Overall the present findings demonstrated the close interactions between the roller turbulence and free-surface fluctuations. Future investigations should be carried out over long durations to account for the very slow fluctuations in jump position