Stepped spillway with pre-aeration by a deflector: flow characteristics

Carolina Kuhn Novakoski,Rute Ferla,Eder Daniel Teixeira,Maurício Dai Prá,Marcelo Giulian Marques,Alba Valéria Brandão Canellas

doi:10.1590/2318-0331.252020190051

Carolina Kuhn Novakoski, Rute Ferla + Show 4 more

Open Access

https://doi.org/10.1590/2318-0331.252020190051

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Abstract

ABSTRACT Stepped spillways aim to dissipate part of the upstream energy during the flow passage by the chute. However, the use of these structures is limited to a restrict range of specific discharges due to the risk of cavitation damage. As the air entrainment into the flow assists the concrete protection against the aforementioned damages, a possible solution by aerators installed along the chute, already disseminated to smooth chutes, is being studied to be used also in stepped spillways. The purpose of the present paper is to characterize a flow over a stepped chute with induced aeration by deflector and air supply by an airtight chamber trough tests conducted on a reduced scale physical model. The main regions observed during the tests are presented and were developed four equations that allow to approximately predict the location of the main regions for a given spillway.

Highlights

Stepped spillway structures are an alternative to dissipate a significant amount of flow energy along a chute
Depending on the specific discharge, the boundary layer may not reach the free surface of the flow, the inception point may not occur or occurs far downstream, exposing the chute structure to risks of cavitation damages
Tests conducted in the reduced scale physical model were performed with the purpose of allowing a better understanding of the behavior of a flow over stepped spillway with induced aeration by deflector and air chamber

Summary

Introduction

Stepped spillway structures are an alternative to dissipate a significant amount of flow energy along a chute. This solution allows a reduction of the downstream dissipation structure, resulting in lower total construction cost. In order to ensure energy dissipation and reduce cavitation risks, it is necessary that occurs air entrainment into the flow. Increasing the discharge, the inception point occurs far downstream in relation with lower discharges. Depending on the specific discharge, the boundary layer may not reach the free surface of the flow, the inception point may not occur or occurs far downstream, exposing the chute structure to risks of cavitation damages

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