Effects of Stepped Chute Slope and Slit Location on a Jet from Abrupt Contraction Aerator

Under large unit discharges, stepped chutes are susceptible to cavitation damage due to lack of entrained air. Among various preaeration devices, the simple-structured abrupt contraction aerator (ACA) has a good performance on mild-slope (V:H=1 : 5) stepped chutes with a combined flow pattern consisting of a jet and a local hydraulic jump. To advance the understanding of ACA hydraulics, this paper investigates the effects of stepped chute slope and slit location on jet dynamics. A series of physical experiments were carried out on a steep-slope (V:H=4 : 5) stepped chute with varied slit locations. It was found that a jet was generated by ACA, and sufficiently aerated flow skimmed over the chute bottom with no black water, indicating an effective reduction of cavitation damage. The slit location had little effect on the flow patterns and aeration but might raise the flow profiles and enlarge the jet. Based on the experimental data, the empirical formulas for maximum height and distance of the jet are finally presented to provide references for sidewall design.