Geometric Effects on Discharge Relationships for Labyrinth Weirs

Abstract

Published labyrinth weir design methods, along with specific site constraints, are typically used to develop an appropriate labyrinth weir geometry (footprint, weir height, wall thickness, apex dimensions, sidewall length, sidewall angle, number of cycles, crest shape, etc.) for the desired head-discharge relation. When a proposed labyrinth weir geometry deviates from the underlying design data, uncertainty in hydraulic performance increases and may merit additional guidance or numerical or physical modeling. This study quantifies the effects of systematic variations (apex dimensions, sidewall length, channel width, and weir height) on labyrinth weir hydraulic performance. After considering hydraulic performance, constructability, and economics, an optimum apex width was identified. Hydraulic efficiency was found to decrease with increasing cycle number (for a constant-width channel), and upstream apex geometries were more significant than downstream geometries with respect to hydraulic efficiency. The impact of weir height on hydraulic efficiency was variable, with an overly short weir showing a negative impact and taller weirs being beneficial but only up to a certain height.