American Society of Civil Engineers

Hydraulic Performance of Step Aerator

by Anina Schiess Zamora; formerly, VAW, ETH Zurich, CH-8092 Zurich, Switzerland, Michael Pfister, Ph.D., (Student, VAW, ETH Zurich, Ch-8092 Zurich, Switzerland), Willi H. Hager, F.ASCE, (Prof., VAW, ETH Zurich, CH-8092 Zurich, Switzerland), and Hans-Erwin Minor, (Prof., VAW, ETH Zurich, CH-8092 Zurich, Switzerland)

Journal of Hydraulic Engineering, Vol. 134, No. 2, February 2008, pp. 127-134, (doi:

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Document type: Journal Paper
Discussion: by A. I. Dhatrak E-mail: and et al.    (See full record)
Closure:(See full record)
Abstract: The step aerator for stepped chutes was recently introduced. Its purpose is to preaerate the zone between the spillway crest and the point of incipient bottom aeration to counter cavitation damage for relatively large unit discharges. The shape of the step aerator is optimized herein by hydraulic modeling to design the air supply and to indicate the aerator blockage characteristics. The shape and the performance of the improved step aerator are described in terms of air supply and the development of air-water flow on the stepped chute. Further, step insets are considered to reduce the spray formation on stepped chutes for small unit discharges, in combination with the step aerator. The performance of the step insets was investigated and their effect on the spray formation analyzed. The step aerator generally increases the maximum spray height at smallest discharges as compared to the standard stepped chute without step aerator. Insets over the first five steps significantly reduce spray relative to standard stepped chutes.

ASCE Subject Headings:
Air flow
Hydraulic structures
Water flow