Occurrence and Characteristic Frequencies of Nappe Oscillations at Free-Overfall Structures
Publication: Journal of Hydraulic Engineering
Volume 147, Issue 2
Abstract
The present study investigated the occurrence and characteristic frequency of nappe oscillations on weirs by reanalyzing data from 52 experimental configurations. The considered configurations include various shapes of the weir crest and a range of weir geometric and hydraulic characteristics with two different scales. Nappes were either confined with lateral and back walls forming a nonvented air pocket between the nappe and the weir or unconfined with atmospheric pressure everywhere around the nappe. Oscillations occurred at nappes with uniformly distributed approaching flow of low velocity and unit discharge between 0.01 and , regardless of the model scale. Weir crests that favored nappe oscillations had an upstream profile without geometric discontinuities. A dimensionless frequency of nappe oscillations was expressed as a power function of the ratio of the fall height to the water depth at the point of detachment at the crest, separately for quarter-round and truncated half-round weir crests. The exponents of the two obtained power functions were very close to each other, which allows the usage of their average so that different weir crests exhibit solely offsetting curves.
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Data Availability Statement
All data generated or used during the study are available in a repository online (Lodomez et al. 2020).
Acknowledgments
Maurine Lodomez is grateful to the Fédération Wallonie-Bruxelles for funding her research visit to Utah State University and to Utah Water Research Laboratory for hosting her and enabling the tests on Model 2.
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© 2020 American Society of Civil Engineers.
History
Received: Feb 19, 2020
Accepted: Aug 14, 2020
Published online: Nov 28, 2020
Published in print: Feb 1, 2021
Discussion open until: Apr 28, 2021
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