Velocity and pressure field in skimming flow in stepped spillways

Amador, António; Sánchez‐Juny, Martí; Dolz, Josep; Sánchez-Tembleque, Félix; Puertas, Jerónimo

doi:10.1201/b16994-39

Cited by 11 publications

(9 citation statements)

References 2 publications

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“…Fig. The results were comparable with earlier studies in aerated and nonaerated skimming flows (Chanson and Toombes 2002a;Amador et al 2004;Gonzalez and Chanson 2004). In the present study, the velocity power law exponent was 1/10 on average, although it varied between adjacent step edges.…”

Section: Air-water Velocity and Turbulence Level Distributionssupporting

confidence: 92%

Turbulence characteristics in skimming flows on stepped spillways

Carosi

Chanson

2008

Can. J. Civ. Eng.

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The stepped spillway design is characterized by an increase in the rate of energy dissipation on the chute associated with a reduction of the size of the downstream energy dissipation system. This study presents a thorough investigation of the air-water flow properties in skimming flows with a focus on the turbulent characteristics. New measurements were conducted in a large-size facility (q = 228; step height, h = 0.1 m) with several phase-detection intrusive probes. Correlation analyses were applied to estimate the integral turbulent length and time scales. The skimming flow properties presented some basic characteristics that were qualitatively and quantitatively in agreement with previous air-water flow measurements in skimming flows. Present measurements showed some relatively good correlation between turbulence intensities T u and turbulent length and time scales. These measurements also illustrated large turbulence levels and large turbulent time and length scales in the intermediate region between the spray and bubbly flow regions.Résumé : Les évacuateurs de crues en marches d'escalier sont caractérisés par une taux important de dissipation d'énergie cinétique sur le coursier, et donc, une réduction de la taille du bassin de dissipation aval. Dans cette étude, on présente des séries de mesures détaillées dans l'écoulement diphasique eau-air, avec de nouvelles mesures des propriétés turbulentes. Ce travail a été réalisé dans une modèle physique de grande taille (q = 228, h = 0,1 m) avec plusieurs sondes de mesures intrusives. L'application d'analyses corrélatives fournit des mesures de longueur et temps integrale turbulent. Les résultats de l'étude sont en accord qualitatifs et quantitatifs avec des études précédentes en écoulements extrèmement turbulents (« skimming flows »). On montre une corrélation relativement bonne entre les intensités turbulentes T u et les échelles intégrales turbulentes de longueur et de temps. Les résultats suggèrent un mécanisme de dissipation turbulente dans la région intermédaire entre la région d'écoulement à bulles et la région d'écoulement à gouttes.Mots-clés : turbulence, coursier en marches d'escalier, écoulement extrèmement turbulent, dissipation d'énergie.

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Section: Air-water Velocity and Turbulence Level Distributionssupporting

confidence: 92%

Turbulence characteristics in skimming flows on stepped spillways

Carosi

Chanson

2008

Can. J. Civ. Eng.

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“…In Figure 7C, the turbulence levels range from 0.2 to 1.1 with a mean value of about 50%. The values were consistent with turbulence levels measured in steady stepped chute flows (Ohtsu and Yasuda 1997, Chanson and Toombes 2002b, Amador et al 2004). Note, however, that turbulent velocity data were meaningful only for more than 10 successful interface detections ( Fig.…”

Section: Chanson H (2005) "Air-water and Momentum Exchanges In Unssupporting

confidence: 75%

Air–water and momentum exchanges in unsteady surging waters: An experimental study

Chanson

2005

Experimental Thermal and Fluid Science

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Flood waves resulting from dam breaks and flash floods have been responsible for numerous losses. In the present study, sudden flood releases were investigated down a large flume with a succession of abrupt drops. A new experimental technique was developed to obtain instantaneous void fractions, bubble count rates and velocities using arrays of conductivity probes. The results showed the surge propagating as a succession of freejets and horizontal runoff flow motion downstream of each abrupt drop. A strong aeration of the surge leading edge was observed for all investigated flow conditions. In the horizontal runoff region, instantaneous velocity measurements highlighted an unsteady turbulent boundary layer. Practically, the study provides new information on free-surface aeration in surging waters in channels and on beach slopes.

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“…The data indicated very high turbulence levels, with maximum values above 100 %. These values were consistent with turbulence intensities in wake flows between rocks obtained by Sumer et al (2001) and in the clear water zone of skimming flows by Ohtsu and Yasuda (1997) and Amador et al (2004). The data suggested higher turbulence in stepped chute skimming flows than in smooth chute clear-water flows.…”

Section: Turbulence Intensity and Bubble Count Ratesupporting

confidence: 78%

Flow resistance and design guidelines for embankment stepped chutes

Gonzalez¹,

Chanson²

2006

Dams and Reservoirs, Societies and Environment in the 21st Century, Two Volume Set

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Recently the design flows of many dams have been re-evaluated, resulting in spills often larger than the original ones. In many cases, occurrence of revised flows would result in dam overtopping because of insufficient storage and spillway capacity of reservoirs. Embankment dams whilst common are more likely to fail than other dam types when overtopped in an uncontrolled manner because of breaching or complete erosion of the downstream face of the embankment. Despite the catastrophic effects of dam failure, dam overtopping constitutes still most identified collapses. Stepped chutes with moderate slopes represent a convenient embankment overtopping protection because of its large energy dissipation potential and its compatibility with recent construction methods (RCC, rip-rap gabions). New experimental flow resistance results are presented herein to help designers to predict accurately energy dissipation on moderate slope stepped chutes. Some recent advances in design guidelines are also discussed.

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Velocity and pressure field in skimming flow in stepped spillways

Cited by 11 publications

References 2 publications

Turbulence characteristics in skimming flows on stepped spillways

Turbulence characteristics in skimming flows on stepped spillways

Air–water and momentum exchanges in unsteady surging waters: An experimental study

Flow resistance and design guidelines for embankment stepped chutes

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