Effects of a Labyrinth Weir with Outlet Ramps on Downstream Steep-Stepped Chute Sidewall Height Requirements

Abstract Labyrinth weirs are commonly used to increase the capacity of existing spillways and provide more efficient spillways for new dams due to their high specific discharge capacity compared to the linear weir. In the present study, experimental and numerical investigation was conducted to improve the rectangular labyrinth weir performance. In this context, four configurations were tested to evaluate the influence of the entrance shape and alveoli width on its discharge capacity. The experimental models, three models of rectangular labyrinth weir with rounded entrance and one with flat entrance, were tested in rectangular channel conditions for inlet width to outlet width ratios (a/b) equal to 0.67, 1 and 1.5. The results indicate that the rounded entrance increases the weir efficiency by up to 5%. A ratio a/b equal to 1.5 leads to an 8 and 18% increase in the discharge capacity compared to a/b ratio equal to 1 and 0.67, respectively. In addition, a numerical simulation was conducted using the opensource CFD OpenFOAM to analyze and provide more information about the flow behavior over the tested models. A comparison between the experimental and numerical discharge coefficient was performed and good agreement was found (Mean Absolute Relative Error of 4–6%).

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Performance Advantages of Labyrinth Weir

International Journal of Innovative Technology and Exploring Engineering - Special Issue ◽

10.35940/ijitee.b1008.1292s219 ◽

2019 ◽

Vol 9 (2S2) ◽

pp. 26-29

Keyword(s):

Control Flow ◽

Water Bodies ◽

Labyrinth Weir ◽

Common Structure ◽

Water Courses ◽

Coefficient Of Discharge ◽

Labyrinth Weirs

Weir is a very common structure across water courses to control flow and to release surplus water from water bodies. Simple straight weirs are less efficient compared to labyrinth weir where the weir length is increased by folds. In this research, experiments were conducted in the laboratory to find the increase in discharge due to labyrinth or decrease in coefficient of discharge due to labyrinth. Further two labyrinth weirs were analyzed to understand the efficiency with respect to the shape of the labyrinth weir. Compared to the ogee weir, the labyrinth weir discharges more water (more than 60%) for the same head of flow.

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Flow over a stepped chute with and without macro-roughness elements

Canadian Journal of Civil Engineering ◽

10.1139/l04-059 ◽

2004 ◽

Vol 31 (5) ◽

pp. 880-891 ◽

Cited By ~ 12

Author(s):

Mehmet Ali Kökpinar

Keyword(s):

Water Flow ◽

High Speed ◽

Length Distribution ◽

Air Entrainment ◽

Air Concentration ◽

Bubble Frequency ◽

Two Phase ◽

Air Bubble ◽

Roughness Elements ◽

Stepped Chute

High-speed two-phase flows over a 30° stepped flume were experimentally investigated using macro-roughness elements. The roughness elements included combinations of steps and horizontal strips. Local values of air concentration, air bubble frequency, and mean chord lengths were measured by a fiber-optical instrumentation system in the air–water flow region. The range of unit discharge of water was varied from 0.06 to 0.20 m2/s. Three step configurations were studied: (i) without macro-roughness elements, (ii) with macro-roughness elements on each step, and (iii) with macro-roughness elements on each second step (AMR configuration). The results were compared in terms of onset flow conditions and internal air–water flow parameters such as local air concentration, mean air bubble chord length distribution, and air bubble frequency in the skimming flow regime. It was observed that the AMR configuration produced the maximum free-surface aeration among the other configurations. This alternative step geometry has potential for less cavitation damage than conventional step geometry because of the greater air entrainment.Key words: stepped chute, air-entrainment, air-water flow properties, macro-roughness elements, skimming flow.

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