TECHNICAL NOTES Air uptake along the lower nappe of a spillway aerator

Lima, Alberto Carlos de Melo

doi:10.3826/jhr.2008.3296

Cited by 3 publications

(2 citation statements)

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“…The upper and lower boundaries of the domain were set at two conditions: 1) C values of 95% and 5%, and 2) C values of 90% and 10%. Lima et al (2008) showed that the measured air discharges are substantially lower than the air discharges evaluated from the concentration profiles. Previous results of Wilhelms and Gulliver (2005), when evaluating entrained air from concentration profiles for upper surface aeration, showed that corrections must be made because the measurements involve air among water parcels of the surface distortions, not absorbed by the water.…”

Section: Upper Boundarymentioning

confidence: 97%

“…Previous results of Wilhelms and Gulliver (2005), when evaluating entrained air from concentration profiles for upper surface aeration, showed that corrections must be made because the measurements involve air among water parcels of the surface distortions, not absorbed by the water. Lima et al (2008) suggested that a similar effect influenced the measurements along the lower nappe, with the addition of the effect of the spray that emanates from the aerator lip as water. Substantial sprays could account for water measurement throughout the air pocket, affecting the air discharge results.…”

Section: Upper Boundarymentioning

confidence: 99%

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Lower nappe aeration in smooth channels: experimental data and numerical simulation

Arantes

Porto²,

Gulliver

et al. 2010

An. Acad. Bras. Ciênc.

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Bed aerators designed to increase air void ratio are used to prevent cavitation and related damages in spillways. Air entrained in spillway discharges also increases the dissolved oxygen concentration of the water, which can be important for the downstream fishery. This study considers results from a systematic series of measurements along the jet formed by a bed aerator, involving concentration profiles, pressure profiles, velocity fields and corresponding air discharges. The experimental results are, then, compared, with results of computational fluid dynamics (CFD) simulations with the aim of predicting the air discharge numerically. Comparisons with jet lengths and the air entrainment coefficients from the literature are also made. It is shown that numerical predictive tools furnish air discharges comparable to measured values. However, if more detailed predictions are desired, verification experiments are still necessary.

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Section: Upper Boundarymentioning

confidence: 97%

Section: Upper Boundarymentioning

confidence: 99%

Lower nappe aeration in smooth channels: experimental data and numerical simulation

Arantes

Porto²,

Gulliver

et al. 2010

An. Acad. Bras. Ciênc.

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Air entrainment mechanism of chute bottom aerators in high-speed chute flows

Wei

2022

Physics of Fluids

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In high-head dam projects, chute aerators are commonly applied as artificial aeration devices to prevent cavitation erosion damage in high-speed spillway and tunnel flows. These specific chute air-water flows are generated by jet lower-surface aeration above the bottom cavity and jet impact aeration on the bottom floor. These air entrainment processes determine the total air flux transport downstream of the chute flow. However, the differential air fluxes caused by the two different aeration mechanisms remains unclear. Based on physical model investigations, the two air entrained processes are observed by a high-speed camera, and detailed air flux data are measured in the aerator cavity and impact areas. The effects of the jet lower-surface disintegrating and then instantaneously reattaching to the chute floor are discussed. The measured air flux data indicate that the inertial jet impact entrainment dominates with increasing Froude number, while the air flux proportion of the jet lower-surface aeration increases with the aerator height. A general prediction model for aerator cavity entrainment is proposed, considering the effects of the Froude number and jet lower-surface aeration. The scale effects of the coupling mechanism on chute aerator air entrainment highlight that aerator cavity air entrainment primarily depends on the inertial jet impact, and the main effects of aerator design on entrainment performance are manifested in the air cavity properties.

TECHNICAL NOTES Air uptake along the lower nappe of a spillway aerator

Cited by 3 publications

References 0 publications

Lower nappe aeration in smooth channels: experimental data and numerical simulation

Lower nappe aeration in smooth channels: experimental data and numerical simulation

Air entrainment mechanism of chute bottom aerators in high-speed chute flows

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