LIDAR measurements of free-surface characteristics in a hydraulic jump

Hydraulics jumps occur at the flow transition from fast flowing supercritical flows to slow moving subcritical flows. Hydraulic jumps are characterised by strong flow turbulence, flow aeration and fluctuations of the free-surface. Herein new laboratory experiments were conducted with an industrial LIDAR to provide an improved understanding of the free-surface features in a hydraulic jump with strong flow aeration. The LIDAR allowed a continuous recording of the free-surface features in channel centreline with a high spatial and temporal resolution. The present results showed a close agreement of the present observations with comparable experimental studies with different instrumentation in terms of mean free-surface profiles, standard deviations of free-surface fluctuations, as well as characteristic frequencies of jump toe oscillations and free-surface fluctuations. The close agreement of the LIDAR data with previous studies validated the use of a LIDAR for free-surface measurements in aerated hydraulic jumps providing new opportunities for future research of free-surface characteristics in hydraulic jumps.