Author(s): Lisa Luddecke; Mario Oertel
Linked Author(s): Mario Oertel
Keywords: Non-linear Weir Labyrinth Weir State-of-the-art Research deficit
Abstract: Abstract Non-linear weirs differ from linear weir structure design due to their folded geometry. The resulting extended crest length allows a more efficient discharge behavior with smaller upstream water levels. The first design of a non-linear weir was presented in 1940 as the Labyrinth Weir. Since then this weir structure has been topic of many studies investigating its geometry, flow behavior and stability. The geometric design, velocities and energy dissipation as well as pressure fluctuations and debris blocking next to numerous other topics have been part of intensive research investigations. In the meantime, prototype structures were built in several countries resulting in a better understanding of these structures under prototype conditions. However, there are still research questions concerning these structures that remain to be answered. Therefore, this paper provides an overview of the research carried out for Labyrinth Weir geometries until today. A quantitative analysis concerning the type of research and publication as well as the studied topics and findings are presented. Finally, research deficits are addressed and ideas for further studies are presented. Keywords: Non-linear Weir; Labyrinth Weir; State-of-the-art; Research deficit. Introduction Labyrinth Weirs were first presented in the 1940s by Gentilini (1940) as a weir that is characterized by a broken axis in plan with the total crest length being compressed in concertina from the space available on site (see Fig. 1). With the resulting extended crest length, a better discharge capacity can be achieved since the efficiency of a weir is directly proportional to its crest length (Taylor 1968). Labyrinth weirs have been built since then with the main aim to maximize discharge capacity at relatively low upstream heads in order to minimize flooding upstream of the weir during flood events. Concurrently, research has been intensified to continuously improve these hydraulic structures (Houston 1982 and Houston 1983). A significant portion of the research was dedicated to enhance the efficiency of these weirs. Adaptions of the geometry concerning wall thickness, key width and key ratios, general shape and other parameters were analyzed. Tests were conducted and tested to focus on the influence on discharge coefficients, which presents an indicator for the efficiency of the weir following the standard weir equation (Ben Said 2011, Falvey 2002, Tullis 2005 and others): Q=2/3∙L∙c_D∙√ (2∙g) ∙〖H_t〗^ (3⁄2) (1) where Q is the discharge, L is the centerline crest length, cD is a dimensionless discharge coefficient, g is the acceleration due to gravity and Ht is the total upstream energy head defined as Ht = v2/ (2g) + ht with v as the mean upstream flow velocity and ht as the overfall height above the weir’s crest. Compared to gated weirs, Labyrinth Weirs feature relatively low construction and maintenance costs. They are therefore often constructed on top of dams to increase storage volume and to increase the spillway capacity of existing dams (Schleiss 2011). Moreover, Labyrinth Weirs have also been built as in-channel applications. Both types of installation are still being investigated in various studies for their different influences on flow properties. The purpose of this paper is to review previously published studies on Labyrinth Weirs and to quantify and analyze the research work that has been carried out to date. Fig. 1. Geometrical parameters of a Labyrinth Weir. Quantitative and content analysis of research on Labyrinth Weirs More than 200 publications have been viewed, and the study will continue to include publications published in 2024 for flow analysis research of Labyrinth Weirs. The paper addresses two types of analysis, commencing with a quantitative analysis. This entails quantifying the type of publication, year of publication, type of research, and the investigation method. Moreover, the research topics investigated, the shape of the Labyrinth Weir, and the type of installation are classified. The quantitative evaluation demonstrates the areas of focus for research on Labyrinth Weirs in recent years and identifies remaining research gaps. Results will be presented in the form of spider graphs, as exemplary illustrated in Figs. 2 and 3. Fig. 2. Year of publications on Labyrinth Weirs. Fig. 3. Type of publication and type of investigated Labyrinth Weir. In the second part of the study, the research topics will be subjected to a more detailed analysis, with a particular focus on the investigations that have been conducted and the results that have been obtained. In this section, the findings on discharge efficiency and geometry optimization, general flow behavior, pressure fluctuations and oscillation, as well as scour, sediment transport and floating debris and debris blocking will be presented. Conclusion and Outlook Despite the extensive research conducted on Labyrinth Weirs and the numerous studies that have been conducted to examine various aspects of this hydraulic structure, there remain areas and topics that have not yet been adequately addressed. In conclusion, the study will present the identified research deficits and suggest potential future research topics. References Ben Said, M. ; Ouamane, A. (2011) Study of optimization of labyrinth weir. In: Erpicum, Laugier et al. (Hg. ) 2011 – Labyrinth and Piano Key Weirs. Falvey, H. T. (2002) Hydraulic Design of Labyrinth Weirs. Gentilini, B. (1940) Stramazzi con cresta a piiiata oblique e a zig-zag. Memorie e studi dell Instituto di Idraulica e Costruzioni Idrauliche del Regio Politecnico di Milano. No. 48. (in Italian). Houston, K. I. (1982) Hydraulic Model study of Ute Dam Labyrinth Spillway. Houston, K. I. (1983) Hydraulic Model Study of Hyrum Dam Auxiliary Labyrinth Spillway. Schleiss, A. J. (2011) From Labyrinth to Piano Key Weirs – A historical review. In: Erpicum, Laugier et al. (Hg. ) 2011 – Labyrinth and Piano Key Weirs. Taylor, G. (1968) The performance of Labyrinth Weirs. Tullis, B. P. ; Willmore, C. M. ; Wolfhope, J. S. (2005) Improving Performanc
Year: 2025