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

Abstract

<jats:p>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.</jats:p>

Induced aeration flow over stepped spillways: mean pressures, air entrainment and flow behavior

“…The flow behavior observed was the same as presented by Novakoski et al (2020). The jet impact position verified was downstream from deflector II as related to deflector I.…”

“…The characteristic positions of the flow, as shown in In Figures 8 and 9, as described by Novakoski et al (2020), the jet impact (L jet ) is the point where the jet originated by the deflector reaches the chute, causing a peak of mean pressures. The blackwater end (L bw ), is the place where the blackwater core ends and gradually varied flow beginning (L vf ) is the position where the gradually varied flow begins.…”

“…Air can be inserted into the flow by aerator elements such as piers and deflectors combined with an air supply system. Authors such as Dong et al (2019), Koen et al (2019), Ma & Wu (2021) and Priebe et al (2021) studied the aeration induced in stepped spillways by piers and Pfister et al (2006a), Pfister et al (2006b), Mojtaba et al (2015), Terrier (2016), Novakoski et al (2020) and Ferla et al (2021) with deflectors.…”

Stepped spillways with aerators: hydrodynamic pressures and air entrainment

“…Concerning the point of installation of the aerator system along the chute, most investigations consider placing the aerator in the vicinity of the spillway (e.g., Pfister et al, 2006aPfister et al, , 2006bZamora et al, 2008;Mojtaba et al, 2015;Novakoski et al, 2020). Other works also consider installing the aerator system further downstream of the chute, however, suggesting the existence of a smooth chute upstream (e.g., Terrier, 2016).…”