Author(s): K. W. Frizell; F. M. Renna
Linked Author(s): Kenneth Warren Frizell
Keywords: Stepped spillway; Cavitation; Friction coefficient; Macro-roughness
Abstract: The development of roller-compacted concrete (RCC) in the 1980's spurred a resurgence in the design and construction of stepped spillway chutes worldwide. New designs have stretched the limits on head and specific discharges, resulting in renewed discussions of cavitation potential. The uncertainty of cavitation formation and possible damage has led to conservative design approaches to limit specific discharge and include forced aeration ramps. Atmospheric and reduced-pressure modelling were performed at the Bureau of Reclamation's Denver laboratory on a sectional model of a stepped spillway for two channel slopes and one step height. Extensive measurements were used to characterize basic parameters such as friction factor, mean flow and time-averaged turbulence properties as well as the incipient cavitation index. The results show that cavitation can form in nonaerated flows on stepped spillways and the incipient cavitation index is related to the friction coefficient Cf of these uniformly distributed macro-roughness elements.
Year: 2011