Publication

Effect of an abrupt slope change on air entrainment and flow depths at stepped spillways

Anton Schleiss, Michael Pfister, José Pedro Gamito de Saldanha Calado Matos, Mohammad Javad Ostad Mirza
2017
Journal paper

Abstract

Several stepped spillways have been built in recent decades, mostly integrated in the downstream faces of roller compacted concrete dams. Among them, only a few have changing bottom slopes. Comprehensive information on the effect of a slope change on the flow features is lacking. This paper reports a systematic study of air entrainment and flow bulking in skimming flow along stepped spillways in the vicinity of abrupt slope changes. Physical modelling was conducted using a large facility with abrupt pseudo-bottom slope changes from 50° to 30° and from 50° to 18.6°. Air–water flow measurements were conducted at several flow cross-sections upstream and downstream of the slope change. The results indicate a significant influence of the slope change on the air pattern and flow bulking. Four main flow sub-regions were identified to describe the typical air–water flow patterns. The normalized length of the influence reach induced by the slope change was found to depend mainly on the critical flow depth, regardless of the slope change and step height.

Official source

https://infoscience.epfl.ch/record/228271?ln=en

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Related concepts (15)

Spillway

A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure that water does not damage parts of the structure not designed to convey water. Spillways can include floodgates and fuse plugs to regulate water flow and reservoir level. Such features enable a spillway to regulate downstream flow—by releasing water in a controlled manner before the reservoir is full, operators can prevent an unacceptably large release later.

Dam

A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aquaculture, and navigability. Hydropower is often used in conjunction with dams to generate electricity. A dam can also be used to collect or store water which can be evenly distributed between locations.

Hoover Dam

Hoover Dam is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Nevada and Arizona. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President Franklin D. Roosevelt. Its construction was the result of a massive effort involving thousands of workers, and cost over 100 lives. It was referred to as the Hoover Dam after President Herbert Hoover in bills passed by Congress during its construction; it was named the Boulder Dam by the Roosevelt administration.

Related publications (8)

Effect of 30-Degree Sloping Smooth and Stepped Chute Approach Flow on the Performance of a Classical Stilling Basin

Anton Schleiss, Michael Pfister, José Pedro Gamito de Saldanha Calado Matos, Ivan Stojnic

Advances in dam construction techniques have significantly increased the number of stepped spillways implemented worldwide. Although stepped chutes provide enhanced energy dissipation along the chute, as compared to smooth chutes, an adequate energy dissip ...

2020

Experimental study on the influence of abrupt slope changes on flow characteristics over stepped spillways

Mohammad Javad Ostad Mirza

Application of stepped spillways increases the energy dissipation rate along the spillway and may reduce the dimensions of the terminal energy dissipation structure. This pronounced energy dissipation makes stepped chutes attractive under various condition ...

EPFL2016

Hydraulic performance of stepped spillway aerators and related downstream flow features

Stéphane Christian Olivier Terrier

To protect spillways against cavitation damage, adding a small air concentration to the flow close to the invert is efficient. Aerator performance on smooth chutes was therefore well studied in terms of air entrainment and downstream air concentration deve ...

EPFL2016

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