Air-Water Flow Properties in Hydraulic Jumps With Fully and Partially Developed Inflow Conditions

Novel air-water flow measurements were conducted in fully aerated hydraulic jumps with partially and fully developed supercritical inflow conditions. Irrespective of the inflow conditions, the hydraulic jumps resembled typical flow patterns with strong aeration and instabilities, albeit hydraulic jumps with fully developed inflow conditions had a more upward directed roller motion and a larger clear water core in the second half of the roller. Hydraulic jumps with fully developed inflow conditions had comparatively larger void fractions in the first half of the jump roller and larger bubble count rates throughout, while a comparatively larger number of smaller bubble sizes suggested a stronger break-up of bubbles. This was consistent with slightly larger interfacial velocities and turbulence intensities in the first half of the jump roller with fully developed inflow conditions. An assessment of the required sampling duration for air-water flow properties indicated the requirement to sample for at least five times longer than applied in previous studies. These results highlighted the need to carefully consider the inflow conditions and sampling parameters for aerated hydraulic jumps.