Air entrainment and turbulence in hydraulic jumps: Free-surface fluctuations and integral turbulent scales

Abstract: An open channel flow can change from a supercritical to subcritical flow with a strong dissipative process: a hydraulic jump. Herein some new measurements of free-surface fluctuations next to the jump toe and integral turbulent scales in the roller are presented with a focus on turbulent hydraulic jumps with a marked roller. The results highlighted the fluctuating nature of the impingement perimeter in terms of both longitudinal and transverse locations. The air-water flow measurements highlighted the intense flow aeration. The turbulent velocity distributions presented a shape similar to a wall jet solution, and the integral turbulent length scale distributions exhibited a monotonic increase with increasing vertical elevation within 0.2 < Lz/d1 < 0.8 in the shear layer, where Lz is the integral turbulent length scale and d1 the inflow depth.