Journal
JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING
Volume 138, Issue 8, Pages 757-765Publisher
ASCE-AMER SOC CIVIL ENGINEERS
DOI: 10.1061/(ASCE)IR.1943-4774.0000466
Keywords
Labyrinth weir; Labyrinth weir nappe interaction; Local submergence; Labyrinth weir nappe interference regions; Labyrinth weir apex influences; Local submergence
Funding
- State of Utah
- Utah Water Research Laboratory (Utah State University)
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The interaction of nappes from adjacent weir walls near an upstream apex can cause local submergence, which reduces labyrinth weir discharge efficiency. Local submergence effects can cause the head-discharge relationships for labyrinth weirs of equivalent lengths but different cycle numbers to differ. Empirical labyrinth weir discharge coefficients implicitly account for apex effects and local submergence; however, the uncertainty associated with applying hydraulic design data developed from specific weir geometries to comparable but different labyrinth weir geometries is not well understood. This study investigates the concept of labyrinth weir nappe interference and identifies labyrinth weir flow characteristics that decrease discharge efficiency, including local submergence. Parametric methods for quantifying nappe interference region size as a function of weir geometry (e. g., sidewall angle and crest shape) and flow conditions (e. g., headwater and nappe aeration) are presented. A comparison between empirical methods found in the literature for determining the size of the nappe interference region and laboratory-scale experimental data showed a limited correlation. The data presented in this study are recommended as a more accurate alternative to predict the extent of the nappe interference region. DOI: 10.1061/(ASCE)IR.1943-4774.0000466. (C) 2012 American Society of Civil Engineers.
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