Turbulence manipulation in air–water flows on a stepped chute: An experimental study

Gonzalez, Carlos A.; Chanson, Hubert

doi:10.1016/j.euromechflu.2007.09.003

Cited by 12 publications

(5 citation statements)

References 20 publications

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“…The dissipated energy contributed to the entrapment and advection of air bubbles within the main flow, as well as to the formation of water droplets and their ejection above the free-surface. The mechanisms were consistent with the experimental results of Gonzalez and Chanson (2008) who observed that some increased rate of energy dissipation induced by passive turbulent manipulation was linked with a greater spray production.…”

Section: Experimental Results: (2) Turbulent Time and Length Scalessupporting

confidence: 81%

Turbulence, dynamic similarity and scale effects in high-velocity free-surface flows above a stepped chute

Felder

Chanson

2009

Exp Fluids

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In high-velocity free-surface flows, air entrainment is common through the interface, and intense interactions take place between turbulent structures and entrained bubbles. Two-phase flow properties were measured herein in high-velocity open channel flows above a stepped chute. Detailed turbulence measurements were conducted in a large-size facility, and a comparative analysis was applied to test the validity of the Froude and Reynolds similarities. The results showed consistently that the Froude similitude was not satisfied using a 2:1 geometric scaling ratio. Lesser number of entrained bubbles and comparatively greater bubble sizes were observed at the smaller Reynolds numbers, as well as lower turbulence levels and larger turbulent length and time scales. The results implied that small-size models did underestimate the rate of energy dissipation and the aeration efficiency of prototype stepped spillways for similar flow conditions. Similarly a Reynolds similitude was tested. The results showed also some significant scale effects. However a number of self-similar relationships remained invariant under changes of scale and confirmed the analysis of Chanson and Carosi (Exp Fluids 42:385-401, 2007). The finding is significant because self-similarity may provide a picture general enough to be used to characterise the airwater flow field in large prototype channels. Cross-correlation time scale ( List of symbols

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Section: Experimental Results: (2) Turbulent Time and Length Scalessupporting

confidence: 81%

Turbulence, dynamic similarity and scale effects in high-velocity free-surface flows above a stepped chute

Felder

Chanson

2009

Exp Fluids

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“…André (2004) experimentally studied pooled stepped spillways with different configurations through which void fraction, velocity and air-entrainment were investigated. Gonzalez and Chanson (2008) conducted experimental studies about stepped spillway in which some steps were equipped with vanes. Their results showed that vanes had a significant effect on air-water flow properties.…”

Section: Introductionmentioning

confidence: 99%

Study of inception point, void fraction and pressure over pooled stepped spillways using Flow-3D

Morovati

Eghbalzadeh

2018

Int Jnl of Num Meth for HFF

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Purpose -While many stepped spillways geometry design guidelines were developed for flat steps, designing pooled steps might be an appropriate alternative to spillways working more efficiency. This paper aims to deal with the inception point of air-entrainment and void fraction in the different height of the pools. Following that, pressure distribution was evaluated in aerated and non-aerated regions under the effect of different heights of the pools and slopes through the use of the FLOW-3D software. Comparison of obtained numerical results with experimental ones was in good agreement for all discharges used in this study. Pools height had the insignificant effect on the inception point location. The value of void fraction was more affected in lower discharges in comparison with higher ones. Negative pressure was not seen over the crest of spillway (non-aerated region), and the maximum pressure values were obtained for pools with 15 cm height along the crest in each discharge. In all slopes, negative pressure was not formed near the step bed in the pooled and flat stepped spillways. However, negative pressure was formed in more area near the vertical face in the flat stepped spillway compared with the pooled stepped spillway which increases the probability of cavitation phenomenon in the flat stepped chute.Design/methodology/approach -A pooled stepped spillway was used in order to evaluate pressure, void fraction, and inception point. Also, different height of the pools was used. Numerical simulation of this study was fulfilled through Flow-3D software. The obtained results indicated that pools can affect two-phase flow characteristics including pressure, void fraction and inception point.Findings -Over the crest, negative pressure was not seen. Pressure values were different for all used heights and the maximum ones obtained for 15 cm height. Also, pooled stepped played a more effective role in reducing the negative pressure points compared with flat cases. Inception point location was more affected in nappe and transition flow regimes in comparison with skimming flow regime particularly for 9 and 15 cm heights.Originality/value -The research results of Felder et al. (2012a) from the University of Queensland were used to numerically simulate the flow over the pooled stepped spillway.

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“…Flows on stepped chutes are characterized by strong energy dissipation and complex interactions between air and water entities within the flows downstream of the inception point of free-surface aeration (e.g. Gonzalez and Chanson, 2008;Bung and Valero, 2016;Felder and Chanson, 2016a;Zhang and Chanson, 2018). Stepped spillways for flood mitigation purposes are typically designed for maximum flow conditions, which take place in the skimming flow regime.…”

Section: Introductionmentioning

confidence: 99%

Nappe flows on a stepped chute with prototype-scale steps height: Observations of flow patterns, air-water flow properties, energy dissipation and dissolved oxygen

Felder

Geuzaine

Dewals

et al. 2019

Journal of Hydro-environment Research

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Turbulence manipulation in air–water flows on a stepped chute: An experimental study

Cited by 12 publications

References 20 publications

Turbulence, dynamic similarity and scale effects in high-velocity free-surface flows above a stepped chute

Turbulence, dynamic similarity and scale effects in high-velocity free-surface flows above a stepped chute

Study of inception point, void fraction and pressure over pooled stepped spillways using Flow-3D

Nappe flows on a stepped chute with prototype-scale steps height: Observations of flow patterns, air-water flow properties, energy dissipation and dissolved oxygen

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