The mechanism of air bubble entrainment in self-aerated flow

Volkart, Peter U.

doi:10.1016/0301-9322(80)90003-8

Cited by 53 publications

(27 citation statements)

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“…These results are consistent with observations [15,19,21]. HALBRONN et al [19] observed "only extremely fine bubbles" (i.e.…”

Section: Appendix 1 Bubble Breakup In Self-aerated Flowssupporting

confidence: 93%

“…Little information is available on the size of the water droplets surrounded by water. Photographs suggest that the droplet sizes are of similar size as the large air bubbles [21] and equation (11) estimate of the droplet sizes. It must be emphasised that the contribution of large particles (bubbles or droplets) to the interface area is relatively small.…”

Section: Air-water Interface Areamentioning

confidence: 84%

“…In the upper flow region, high speed photographs [21,36] showed overturning surface waves and water droplets being projected above the water surface and then falling back. KILLEN [36] discussed the concept of "air entrained flows" near the water surface.…”

Section: Appendix 2 Definition Of An Ideal Air-water Interfacementioning

confidence: 99%

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Predicting Oxygen Content Downstream of Weirs, Spillways and Waterways.

Chanson¹

1995

Proceedings of the Institution of Civil Engineers - Water, Mari

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At hydraulic structures (e.g. weirs, spillways), air-water transfer of atmospheric gases (e.g. oxygen) occurs by self-aeration along the chute and by flow aeration in the hydraulic jump at the downstream end of the structure. In this paper, experimental data are re-analysed and compared with a numerical method to predict the free-surface aeration. Aeration at hydraulic jumps is also examined and compared with existing correlations. Calculations of free-surface aeration and empirical correlations for hydraulic jump aeration are combined to predict the DO content downstream of weirs and spillways. Good agreement between calculations and prototype data is obtained. The results indicate that self-aeration might contribute to a large part of the oxygenation taking place at hydraulic structures for small water discharges. For large discharges, the reduction or the disappearance of free-surface aeration affects substantially the aeration efficiency.

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“…These results are consistent with observations [15,19,21]. HALBRONN et al [19] observed "only extremely fine bubbles" (i.e.…”

Section: Appendix 1 Bubble Breakup In Self-aerated Flowssupporting

confidence: 93%

Section: Air-water Interface Areamentioning

confidence: 84%

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Predicting Oxygen Content Downstream of Weirs, Spillways and Waterways.

Chanson¹

1995

Proceedings of the Institution of Civil Engineers - Water, Mari

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“…Local aeration by impinging jets is also very common, with vortices in the intensive shear layer at the penetration point strong enough to entrain air at their core. Volkart (1980) experimentally analysed the mechanism of air bubble entrapment in self-aerated flows in a steep partially filled pipe, using a stroboscopic technique. He found that the air bubble consequent to drops impinging on the water surface is always bigger than the pertinent water drop and also computed the minimum vertical distance of a water drop in order to form an air bubble.…”

Section: The Effect Of Air Entrapmentmentioning

confidence: 99%

Turbulence in the swash and surf zones: a review

Longo

Petti

Losada

2002

Coastal Engineering

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This paper reviews mainly conceptual models and experimental work, in the field and in the laboratory, dedicated during the last decades to studying turbulence of breaking waves and bores moving in very shallow water and in the swash zone. The phenomena associated with vorticity and turbulence structures measured are summarised, including the measurement techniques and the laboratory generation of breaking waves or of flow fields sharing several characteristics with breaking waves. The effect of air entrapment during breaking is discussed. The limits of the present knowledge, especially in modelling a two-or three-phase system, with air and sediment entrapped at high turbulence level, and perspectives of future research are discussed. D

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“…In general, drops remain stable if W D < 10-12, whereas they break-up by different mechanisms for higher values (Krzeczkowski 1980, Hwang et al 1996. Volkart (1980) observed in self-aerated model flows that ejected drops "larger than 6 mm [. .…”

Section: Scale Effectsmentioning

confidence: 99%

Deflector-jets affected by pre-aerated approach flow

Pfister

Hager

2012

Journal of Hydraulic Research

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Jets generated at chute ends move a potential scour zone away from the dam, and dissipate flow energy to reduce the scour. Usually, so-called flip buckets or ski jumps are provided to generate jets, yet they are rarely issued by deflectors. The application of a theoretical mass point parabola is limited to predict the jet features, because effects related to the take-off angle and the disintegration process affect the jet air transport and trajectories. This research discusses the effect of pre-aeration of the approach chute flow on the jet features. A comparison with a former study indicates that mainly the upper jet portion is affected, that the black water jet core becomes shorter, and that the air transport increases. Although the lower trajectory is less affected and thus remains more coherent, the small effect of pre-aeration is sufficient to reduce the total jet throw length, so that pre-aerated jets tend to be shorter as compared with black-water approach flow jets, in agreement with prototype observations.

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The mechanism of air bubble entrainment in self-aerated flow

Cited by 53 publications

References 1 publication

Predicting Oxygen Content Downstream of Weirs, Spillways and Waterways.

Predicting Oxygen Content Downstream of Weirs, Spillways and Waterways.

Turbulence in the swash and surf zones: a review

Deflector-jets affected by pre-aerated approach flow

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