Author(s): Pfister Michael; Hager Willi H.; Minor Hans-Erwin
Linked Author(s): Willi H. Hager, Michael Pfister
Keywords: Erator; Air-water flow; Cavitation; Hydraulic structures; Spray; Stepped spillway. 1
Abstract: A step aerator for stepped chutes pre-aerates the zone between the spillway crest and the point of incipient bottom aeration to counter possible cavitation damage for relatively large unit discharges. The shape of the step aerator was optimized using a hydraulic model by accounting for an adequate air supply and by avoiding aerator blockage. The performance of the step aerator is described in terms of the air supply and the development of the air-water flow on the stepped chute. Modified step shapes were also considered using step insets to reduce the spray on the upper section of the stepped chutes for small unit discharges, in presence of the step aerator. The performance of the modified steps was investigated and their effect on the spray formation analyzed. It was found that step insets over the first five steps reduce significantly spray relative to standard-shaped stepped chutes.