Drag reduction in skimming flow on stepped spillways by aeration
نویسندگان
چکیده
منابع مشابه
Drag reduction in skimming flow on stepped spillways by aeration Réduction du frottement des écoulements écumant sur les seuils en marches d’escalier par aération
In skimming flows on stepped spillway, flow resistance is predominantly a form drag process. Cavity recirculation and air entrainment are intense. The interactions between entrained air bubbles and mixing layers may cause some reduction in flow resistance. The paper presents new evidence showing a reduction in friction factor in skimming flow with increasing free-surface aeration. The experimen...
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Numerous stepped spillways were built to date, namely on RCC gravity dams or on valley flanks besides embankment or rockfill dams, while some others are currently under design or construction. In some cases, slope changes may be required on stepped chutes, due to the topography, leading to reduced excavation and related economic benefits. A quite limited number of stepped spillways have been bu...
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Current expertise in air-water turbulent flows on stepped chutes is limited to laboratory experiments at low to moderate Reynolds numbers on flat horizontal steps. In this study, highly turbulent air-water flows skimming down a large-size stepped chute were systematically investigated with a 22o slope. Turbulence manipulation was conducted using vanes or longitudinal ribs to enhance interaction...
متن کاملFlow aeration, cavity processes and energy dissipation on flat and pooled stepped spillways for embankments
The design floods of several reservoirs were recently re-evaluated and the revised spillway outflow could result in dam overtopping with catastrophic consequences for some embankment structures. Herein a physical study was performed on flat and pooled stepped spillways with a slope typical of embankments (θ = 26.6◦) and four stepped configurations were tested: a stepped spillway with flat horiz...
متن کاملEffects of Step Pool Porosity upon Flow Aeration and Energy Dissipation on Pooled Stepped Spillways
The hydraulics of stepped spillways with flat steps has been studied for the last three decades, including for embankment dam slopes, but studies of alternative stepped designs are limited. In this study, a pooled stepped spillway was investigated in a relatively large-size facility, and three different pool wall porosities were tested. The flow patterns, the macroand microscopic air-water flow...
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ژورنال
عنوان ژورنال: Journal of Hydraulic Research
سال: 2004
ISSN: 0022-1686,1814-2079
DOI: 10.1080/00221686.2004.9728397