The capacity of a labyrinth spillway is a function of the total head, the effective crest length, and the crest coefficient. The crest coefficient depends on the total head, weir height, thickness, crest shape, apex configuration, and the angle of the side legs. Data and a procedure are presented for designing labyrinth weirs for angles between 6° and 35°, and for a range of heads. The design procedure allows the angle of the side legs and the number of cycles to be varied until the desired layout and capacity are achieved. The solution is presented in a spreadsheet format that automatically calculates the dimensions for the labyrinth. Even though the design procedure is quite accurate, it is recommended that the capacity and performance be verified with a model study. The model can evaluate factors not included in the design procedure, like aeration effects at low heads, unusual flow conditions in the approach channel, and flow conditions in the discharge channel.

Design of Labyrinth Spillways

This comprehensive handbook on the hydraulic design of labyrinth spillways—from theory to current practice—presents a state-of-the-art method for the effective design of labyrinth weirs. The book provides a fundamental understanding of the theory of labyrinth weirs and continues with detailed sections on significant factors that affect the discharge characteristics of labyrinth weirs, such as crest shape, weir height, and sidewall angle. The most common design curves are discussed, and from these a recommendation is developed for only one design curve to be used in future designs. But because site conditions often vary so much from ideal conditions described in this book, a section on site-specific modeling criteria is included for making accurate predictions of prototype performance. In its review of past studies, the book closely examines many long-held concepts, especially concerning the idea of interference, nappe oscillation, and the definition of which head to use in design computations, and revises them in an effort to advance current thinking based on the latest research.

Hydraulic Design of Labyrinth Weirs

Low-head labyrinth weir control structures installed on mild sloping channels or where the channel downstream of the weir is constricting and/or heavily vegetated can experience submergence. Weir submergence occurs when the tailwater surpasses the weir crest elevation, causing an increase in the upstream driving head for a given discharge, relative to a free-discharge condition. The most familiar relationship for predicting submerged weir head-discharge relationships is likely that of James R. Villemonte, which he published in 1947 for sharp-crested linear weirs. For lack of a better alternative, Villemonte’s relation has also been applied to predicting submerged labyrinth weir performance. A new dimensionless submerged head relationship developed in this study is presented for submerged labyrinth weirs. A similar relationship is also presented for linear sharp-crested weirs. The accuracy of the submerged linear weir relationship was equivalent to Villemonte’s and is simpler to solve when working in terms...

Head-Discharge Relationships for Submerged Labyrinth Weirs

A method is presented for the hydraulic design and analysis of labyrinth weirs based upon the experimental results of physical modeling. Discharge coefficient data for labyrinth weirs with quarter-round and half-round crest shapes are presented for sidewall angles ranging from 6 to 35°. Cycle efficiency is also introduced as a design aid, which compares the hydraulic performance of different cycle geometries. Geometric parameters that affect flow performance are discussed. The predictive accuracy of the design method is evaluated through comparisons to previously published labyrinth weir head-discharge data. The companion paper examines nappe behaviors that affect flow performance and presents hydraulic design considerations specific to nappe characteristics.

Hydraulic Design and Analysis of Labyrinth Weirs. I: Discharge Relationships

A high level of dissolved oxygen is vital for the maintenance of healthy streams and rivers. Structures in rivers can increase dissolved oxygen levels by creating turbulent conditions where small air bubbles are carried into the bulk of the flow. Plunging overfall jets from weirs are a particular instance of this, and the aeration properties of such structures have been studied widely in the laboratory and field over a number of years. On the other hand, labyrinth weirs, where the weir sill is cranked in planform thus increasing their length, have received little or no attention in this context. They have a proven hydraulic advantage over straight weirs of increased discharge at the same head for design conditions. However, they also serve to modify the combined overfall jet as individual jets from adjacent sections of the weir collide. This paper describes an experimental investigation into the nature of these jets and how they affect the aeration performance of a triangular plan labyrinth weir. It is demonstrated that the aeration efficiency of these labyrinth weirs generally is better than their equivalent-length linear weir and that this advantage becomes more pronounced as the weir included angle becomes smaller and also at lower overfall drop heights and higher discharges. These results point to the possible advantage of these type of weir in situations where both hydraulic and aeration performance needs to be optimized.

Aeration performance of rectangular planform labyrinth weirs

The purpose of the labyrinth weir is to increase the discharge per unit length of structure normally obtained from a conventional weir when operating under identical head conditions. This is achieved by compressing a large length of crest in concertina form, into the space available on site. 

The investigation carried out as described in this thesis aimed to provide comprehensive performance data covering all aspects of labyrinth weir behaviour. This has been achieved by a series of experimental model tests. 

The initial experimental work was confined to basic labyrinth weir configurations and the significance of the parameters of fundamental importance has been determined. This allowed the definition of the most useful ranges of weir design and subsequent experimental tests were confined to within these ranges. 

Following the initial experimental work tests were conducted to determine the significance of all the parameters of secondary importance including various refinements to the weir designs such as sloping channel inverts and alternative crest sections etc. 

A comprehensive set of experimental performance data covering all aspects of labyrinth weir design and behaviour are thus contained in the thesis. 

A mathematical model representing the behaviour of the weirs has been constructed and translated into a computer programme. Close correlation has been achieved between the theoretical and experimental results and the programme will accurately predict the performance of any labyrinth weir subject to some minor restrictions. 

The computer programme is included in the thesis so that it will be available to anyone wishing to use it. 

A design method using two design charts has been developed. This enables the design and performance prediction of any weir designed in accordance with recommendations contained in the thesis. The design charts are included in the text together with a worked example illustrating their use.

Geoffrey Taylor

Papers

The performance of labyrinth weirs