Measuring air-water interface area in supercritical open channel flow

Chanson, Hubert

doi:10.1016/s0043-1354(96)00339-9

Cited by 33 publications

(11 citation statements)

References 5 publications

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“…The ‘aeration effect’ that occurs during the fall of the water increases the area of the air–water interface because the water flows consist of sprays, droplets and broken streams (e.g. Chanson and Cummings, 1996; Chanson, 1997; Zhang and others, 2001; Cheng and others, 2004). The free-falling speed of a raindrop ranges between 1 and 9 m s −1 depending on the size of the droplet (e.g.…”

Section: Modellingmentioning

confidence: 99%

Ice cascade growth and decay: a thermodynamic approach

Gauthier¹,

Montagnat

Weiss

et al. 2013

J. Glaciol.

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ABSTRACT. The ice volume evolution of a frozen waterfall (or ice cascade) was studied using a thermodynamic model. The model was developed from meteorological data collected in the vicinity of the waterfall and validated from ice volume measurements estimated from terrestrial lidar images. The ice cascade forms over a 45 m high rock wall located in northern Gaspésie, Québec, Canada. Two stages of formation were identified. During the first stage, the growth is mainly controlled by air convection around the flowing and free-falling water. The ice cascade growth rate increases with decreasing air temperature below 08C and when the water flow reaches its lowest level. During the second stage, the ice cascade covers the entire rock-wall surface, water flow is isolated from the outside environment and ice volume increases asymptotically. Heat is evacuated from the water flow through the ice cover by conduction. The growth is controlled mainly by the conductive heat loss through the ice cover but also by the longwave radiation emitted at the ice surface during the night. In spring, melting of the ice cascade is dependent on the air convection over the ice surface but also on the sensible heat carried by the increasing water flow and the solar radiation received during the day.

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Section: Modellingmentioning

confidence: 99%

Ice cascade growth and decay: a thermodynamic approach

Gauthier¹,

Montagnat

Weiss

et al. 2013

J. Glaciol.

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“…where the specific interface area for any bubble shape and chord size distribution can be estimated as (Chanson 1997b…”

Section: Introductionmentioning

confidence: 99%

Aeration and air–water mass transfer on stepped chutes with embankment dam slopes

Felder

Chanson

2014

Environ Fluid Mech

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Stepped spillway flows are characterised by significant free-surface aeration downstream of the inception point of air entrainment. The stepped design is advantageous for applications which require large energy dissipation and strong flow aeration. While the energy dissipation rate for embankment stepped spillways was studied previously, the optimum design for aeration and air-water mass transfer is not known. Herein new air-water flow experiments were conducted on several stepped spillways with embankment dam slopes using with phasedetection intrusive probes. The present data were compared with previous studies in terms of energy dissipation, flow aeration and air-water mass transfer. The air-water mass transfer was calculated based upon air-water flow measurements in terms of dissolved oxygen. The re-oxygenation rates were compared with previous studies comprising both conductivity and direct dissolved oxygen measurements. The comparison highlighted a monotonic increase of aeration efficiency with energy dissipation rate. All data were in good agreement independent of channel slopes, stepped configuration and sensor size. The data confirmed the effects of strong air-water interactions within the bulk of the flow for both energy dissipation and re-oxygenation performances.

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“…Equation (1A) is more general than the authors' equation (1) interface area ranging from 10 to 21 m -1 (CHANSON 1997). Larger specific interface areas were recorded in developing shear flows.…”

Section: ∂ ∂Tmentioning

confidence: 88%

Stream Reaeration in Nonuniform Flow: Macroroughness Enhancement

Moog

Jirka

2000

J. Hydraul. Eng.

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The authors presented two papers which are a welcome addition to the topic of water quality and stream re-aeration. The renewal theory and small eddy model provides interesting results for smooth and smallroughness channels. The discussers feel however that the second paper highlights some limits of the method, particularly when free-surface aeration takes place.The present discussion provides additional material on the problem of stream re-aeration in presence of 'white waters' (i.e. air bubble entrainment). It complement the original paper and some references are added including large-scale data. MASS TRANSFER EQUATION AND AIR-WATER INTERFACE AREAThe mass transfer rate of a chemical across an interface varies directly as the coefficient of molecular diffusion and the negative gradient of gas concentration. If the chemical of interest is volatile (e.g. oxygen), the transfer is controlled by the liquid phase and the gas transfer of the dissolved chemical across an air-water interface is rewritten usually as : a by MOOG, D

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Measuring air-water interface area in supercritical open channel flow

Cited by 33 publications

References 5 publications

Ice cascade growth and decay: a thermodynamic approach

Ice cascade growth and decay: a thermodynamic approach

Aeration and air–water mass transfer on stepped chutes with embankment dam slopes

Stream Reaeration in Nonuniform Flow: Macroroughness Enhancement

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