Inception Point and Air Concentration in Flows on Stepped Chutes Lined with Wedge-Shaped Concrete Blocks
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Volume 134, Issue 8
Abstract
Stepped channels lined with wedge-shaped concrete blocks are a promising solution to provide overtopping protection for embankment dams if the discharge capacity of existing spillways is not adequate. The paper addresses the characteristics of the two-phase transition and skimming flows in stepped channels lined with this type of block. An experimental setup was developed with two flumes designed with a relative scale of 1:2.5. Air concentration was measured with an optical probe in several cross sections of both flumes. The scale effects are analyzed. An expression for the location of the inception point is proposed. The vertical air concentration profiles and their longitudinal variation are studied, considering data and models proposed by other researchers. The establishment of the uniform flow regime is analyzed.
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Acknowledgments
The writers acknowledge the financial support for facility construction and general collaboration of the Portuguese Institute of Water (INAG). The first writer wishes to thank the Foundation for Science and Technology for a Ph.D. grant. The writers also wish to acknowledge the fruitful collaboration with the National Laboratory for Civil Engineering (LNEC) and the indispensable support of Dr. J. Falcão de Melo, former Head of the Water Resources and Hydraulic Structures Division LNEC, during the development of the facility. The writers are grateful to Mrs. Kathleen Frizell, from the USBR, for the wedgeshaped blocks research publications provided and for the useful advice given during the paper elaboration.
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Published In
Journal of Hydraulic Engineering
Volume 134 • Issue 8 • August 2008
Pages: 1042 - 1051
Copyright
© 2008 ASCE.
History
Received: Oct 30, 2006
Accepted: Jan 3, 2008
Published online: Aug 1, 2008
Published in print: Aug 2008
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