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Hybrid investigation of labyrinth weirs: Discharge capacity and energy dissipation

  • The replacement of existing spillway crests or gates with labyrinth weirs is a proven techno-economical means to increase the discharge capacity when rehabilitating existing structures. However, additional information is needed regarding energy dissipation of such weirs, since due to the folded weir crest, a three-dimensional flow field is generated, yielding more complex overflow and energy dissipation processes. In this study, CFD simulations of labyrinth weirs were conducted 1) to analyze the discharge coefficients for different discharges to compare the Cd values to literature data and 2) to analyze and improve energy dissipation downstream of the structure. All tests were performed for a structure at laboratory scale with a height of approx. P = 30.5 cm, a ratio of the total crest length to the total width of 4.7, a sidewall angle of 10° and a quarter-round weir crest shape. Tested headwater ratios were 0.089 ≤ HT/P ≤ 0.817. For numerical simulations, FLOW-3D Hydro was employed, solving the RANS equations with use of finite-volume method and RNG k-ε turbulence closure. In terms of discharge capacity, results were compared to data from physical model tests performed at the Utah Water Research Laboratory (Utah State University), emphasizing higher discharge coefficients from CFD than from the physical model. For upstream heads, some discrepancy in the range of ± 1 cm between literature, CFD and physical model tests was identified with a discussion regarding differences included in the manuscript. For downstream energy dissipation, variable tailwater depths were considered to analyze the formation and sweep-out of a hydraulic jump. It was found that even for high discharges, relatively low downstream Froude numbers were obtained due to high energy dissipation involved by the three-dimensional flow between the sidewalls. The effects of some additional energy dissipation devices, e.g. baffle blocks or end sills, were also analyzed. End sills were found to be non-effective. However, baffle blocks with different locations may improve energy dissipation downstream of labyrinth weirs.

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Author:Philipp Langohr, Daniel Bernhard BungORCiD, Brian M. Crookston
ISSN:2521-7119 (print)
ISSN:2521-716X (online)
Parent Title (English):Proceedings of the 39th IAHR World Congress
Publisher:International Association for Hydro-Environment Engineering and Research (IAHR)
Place of publication:Madrid
Editor:Miguel Ortega-Sánchez
Document Type:Conference Proceeding
Year of Completion:2022
Date of the Publication (Server):2024/07/22
First Page:2313
Last Page:2318
39th IAHR World Congress, 19. - 24. Juni 2022, Granada
Institutes:FH Aachen / Fachbereich Bauingenieurwesen
collections:Verlag / International Association for Hydro-Environment Engineering and Research (IAHR)