Skimming Flow in the Nonaerated Region of Stepped Spillways over Embankment Dams
Publication: Journal of Hydraulic Engineering
Volume 135, Issue 8
Abstract
Traditionally, research on stepped spillway hydraulics has been focused on the air-water flow region but for the hydraulic design of small embankment dams experiencing relatively large overtopping flows, the nonaerated region can be very important. Empirical formulas are presented for predicting skimming flow properties upstream of the point of inception of air entrainment for 1V:2H sloping stepped spillways, and the location and flow depth at the point of inception. Particular emphasis is placed on the clear-water depth, velocity distribution, and the energy dissipation characteristics in the developing nonaerated flow region. The velocity distribution is well described by a power law. The normalized clear-water depth and the normalized specific energy varied with the relative distance along the spillway and the effect of the normalized critical depth was negligible. Finally, the rate of energy dissipation was small, which has direct implications for the design of the downstream energy dissipator.
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Acknowledgments
The writers wish to acknowledge the comments of Professor Hubert Chanson. The first writer, formerly Visiting Scholar at UCDavis and financially supported by a Fulbright/FLAD research grant, wants to extend the thanks to Professor Fabián Bombardelli for his advice. The financial support granted by INAG, Portuguese Water Institution (Project No. UNSPECIFIED2003/2029/INAG) and by Fundão para a Cicncia e Tecnologia (FCT) (PhD scholarship SFRH/BD/38003/2007 granted to the first writer), is also acknowledged.
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Information
Published In
Journal of Hydraulic Engineering
Volume 135 • Issue 8 • August 2009
Pages: 685 - 689
Copyright
© 2009 ASCE.
History
Received: Dec 14, 2007
Accepted: Jan 9, 2009
Published online: Jul 15, 2009
Published in print: Aug 2009
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