Abstract
Obstruction of the racks in bottom intakes due to sediment wedged in the slit of the bars can significantly reduce diverted flow. Notwithstanding the design recommendations that are found in the literature, the problem of rack occlusion continues to occur in built structures. This work focuses on the clogging effects in the circular bars of a bottom rack system using gravels whose median diameter, d50, is close to the spacing between the bars. An experimental campaign including 24 tests, each repeated time times, with six different longitudinal slopes from 0 to 35% and four different specific incoming flow rates, q1, in the range of 0.115 to 0.198 m3/s/m, is presented. The results show the inefficiency of circular profiles in comparison with T-shaped bars. No important influence of rack slope is found that could help to reduce clogging. This works confirms the importance of the selection of bar profile to reduce maintenance labor. A comparison of results with previous works with gravel sediment in T-shaped bars is considered. A methodology to calculate the wetted rack length considering occlusion due to flow with sediment transport is proposed, and the results are compared with those in the bibliography.
Highlights
The need to provide water and electricity to populations settled in areas with special geographical, topographic, and hydrological characteristics has led several researchers to focus their attention on the study of bottom intake systems, since stepped torrents (1% < slope < 10%) and laden sediment transport require suitable bottom intake systems for water collection [1]
A methodology is proposed to calculate the length of the rack necessary to completely derive an incoming flow, taking into account the influence of the gravels, Lm0. To calculate this effective wetted rack length, a model was first proposed to obtain the effective void ratio, m0, for any longitudinal slope and incoming flow; the statistical model proposed by Castillo et al [7] was considered and extended for the racks made by circular bars, as presented in Figure 19, including previous results for the case of T-shaped bars
Not quite experimental works are presented in the bibliography to improve knowledge of and avoid this phenomenon
Summary
The need to provide water and electricity to populations settled in areas with special geographical, topographic, and hydrological characteristics has led several researchers to focus their attention on the study of bottom intake systems, since stepped torrents (1% < slope < 10%) and laden sediment transport require suitable bottom intake systems for water collection [1]. In Andean cities which have irregular topography characteristics, the design and construction of bottom intake systems constitute an adequate technical solution for the provision of irrigation water and hydroelectricity. These communities need a water supply for irrigation purposes, to improve and optimize the production of their fields or as a multipurpose project to enhance tourism.
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