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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Water engineering : The effect of cross-waves in physical stepped spillway models
The effect of cross-waves in physical stepped spillway models
Stepped spillways are hydraulic structures with high energy dissipation potential widely used at dams to safely convey
water from upstream to downstream during floods. Their study, in terms of general conception and hydraulic efficiency, in
laboratory scales are being progressively detailed since the 1980s. The focus has been essentially on centre-line of the
stepped spillways and in the uniform flow region. Nonetheless, the influence of the walls in the flow behaviour remains
unexplored and a complete description of the flow depths at the stepped spillways has not been dealt with in depth. This
paper aims to analyse the effect of cross waves in a physical stepped spillway model. Flow depths were measured in an
experimental installation where cross-waves at surface are present, and compared with another experimental structure
where cross-waves do not occur. Three ultrasonic sensors were used to rasterise the flow surface over the stepped
spillway and discover the influence of the walls in the flume¡¯s centre-line. High-speed videos from the flow field were
captured in order to recognise the phenomena of flow pattern alternation between adjacent steps, previously observed by
other authors. This work demonstrates the unequivocal existence of cross-waves in the larger stepped spillway, and their
tentative influence on the flow depths and on the well-known alternating flow pattern over adjacent steps. It was observed
that, by reduction of the spillway width from 0.5 to 0.3 m, where the cross-waves do not exist, the flow pattern alternation
was choked down. Regimes SK1 and SK2 were found in the wide spillway whereas just the regime SK2 was found on the
narrow structure. Comparison in terms of velocities can just be made at steps with identical flow regimes.
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Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Water engineering
Date Published : 12/08/2015
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