Experimental investigation of air entrainment and droplet characteristics in a rectangular jet flow

This experimental study investigates air–water flow properties in a rectangular free-surface jet flow for 4.8 < Fr0 < 11.4, 0.4 × 105 < Re < 2.1 × 105, and 35 < We < 120. Using a dual-tip conductivity probe, measurements of air concentration, bubble count rate, and droplet chord lengths were taken from the cavity to the far-field regions. Results show that air concentration is largely independent of Reynolds number, whereas the bubble count rate exhibits significant scale dependence. The jet flow is divided into four regions from the cavity to the far field, within which the time-averaged air concentration and the maximum bubble count rate exhibit distinct trends. Two formulae to predict the jet thickness and time averaged air concentration within the cavity region are given. Droplet size distributions shift markedly toward finer sprays after jet impingement, influenced by flow turbulence.