Author(s): Lisa Luddecke; Mario Oertel
Linked Author(s): Mario Oertel
Keywords: Non-linear Weir Piano Key Weir State-of-the-art Research deficit
Abstract: ABSTRACT Non-linear weirs are hydraulic structures that can increase the discharge capacity significantly due to its folded geometry compared to regular linear weirs. The design of Labyrinth Weirs was first presented in 1940. In the beginning of the 21th century considerations for a smaller footprint resulted in the introduction of a more advanced geometry of labyrinth weirs – the Piano Key Weir. Since then, many different aspects and issues have been under research to achieve a better understanding of these new structures and to further improve its performance resulting in a large amount of publications on the topic of Piano Key Weirs. To provide a general overview and to quantify the conducted research on Piano Key Weirs, this paper summarizes and categorizes past research activities on Piano Key weirs by an intensive literature review. Classifications regarding type and year of publication, method of investigation as well as investigated topics are evaluated. Furthermore, specific research topics and significant results are presented within a content analysis. Finally, research deficits and future research challenges are identified. Keywords: Non-linear Weir; Piano Key Weir; State-of-the-art; Research deficit. 1. Introduction Since the discharge capacity of a weir is directly proportional to its crest length, a way to increase the efficiency of weirs is to increase the length of the weir’s crest for the same given channel width. With this knowledge non-linear weirs such as Labyrinth Weirs became a major topic of interest to engineers and researchers many years ago (Crookston 2010). Due to their folded geometry, these hydraulic structures have a crest length that is several times longer than that of linear weirs. However, the folded design requires increased space in flow direction which makes it more difficult to build on existing dams. From this reflection a more advanced development of the Labyrinth Weir was introduced by Lemperiere and Ouamane (2003) by introducing the Piano Key Weir (PKW). The PKW is a non-linear weir that offers a smaller footprint due to upstream and downstream overhangs (inlet and outlet keys) with inclined ramps. This geometry not only has the advantage of a smaller footprint and thus the possibility of installation on existing dams, but also increases the discharge capacity compared to Labyrinth Weirs. Meanwhile, numerous research has been published on Piano Key Weirs and it became apparent that these structures had awakened a great amount of interest. Workshops on non-linear weirs have been hold to summarize and share the knowledge on Labyrinth and Piano Key Weirs (Erpicum et al. 2011,2013,2017). Uniform geometric parameters were defined and projects on the implementation of such structures were introduced. Most realized projects can be found in Vietnam, USA and France but also in Australia, Africa, India, Sri Lanka and other parts of Europe PKWs are already built (Universite de Liege 2020). A uniform nomenclature proposed by Pralong et al. (2011) laid the foundation for the determination of the many parameters describing the geometry of a Piano Key Weir as presented in Figure 1. Furthermore, four types of PKW depending on its overhangs have been classified as type A (downstream and upstream overhangs), type B (upstream overhangs), type C (downstream overhangs) and type D (without overhangs) (Erpicum et al. 2017) and different side wall angles lead to variations of the plan shape resulting in a rectangular, triangular and trapezoidal form. To find its most influencing geometrical parameters on discharge efficiency, energy dissipation, scour minimization and other effects as well as to explain its general flow behavior and solve other issues related to this hydraulic structure, the Piano Key Weir has been under great examination resulting in various publications. This paper aims at examining the previously published studies on piano key weirs and quantify and analyze the work that has been done on these structures until today. Fig. 1. Geometrical parameters of a Piano Key Weir, based on Shen and Oertel (2021). 2. Quantitative and content analysis of research on Piano Key Weirs Based on Oertel (2018) the State-of-the-Art for Piano Key Weir research will be investigated continuously. To analyze conducted research on Piano Key Weirs, more than 300 publications have been viewed and more publications being published in 2024 will be included. The study is structured into two categories. First a quantitative analysis is presented, where the type of publication, the year of publication, the type of research and the method of investigation are examined. Furthermore, the investigated research topics and the chosen type and shape of the investigated Piano Key Weir geometry as well as the type of installation are categorized. This evaluation presents the major topics of PKW research of recent years and identifies where research deficits still remain. Results will be visualized in spider diagrams as exemplarily shown in Figure 2 and 3. Fig. 2. Different research topics on Piano Key Weirs. Fig. 3. Type of research and chosen method of investigation of the analyzed publications. In a second part, the research topics will be analyzed in more detail with focus on performed investigations and results. Here, findings on discharge efficiency and geometry optimization, upstream flow behavior, aeration and oscillation, energy dissipation and downstream flow behavior, scour and sediment transport, as well as self-cleaning processes will be presented. 3. Conclusion and Outlook Although a great amount of research has been carried out on Piano Key Weirs and many different studies have been conducted analyzing various aspects concerning this hydraulic structure, there are still fields and aspects that have not yet been sufficiently researched. Finally, as a result of the study, research deficits and needs for future research topics will be presented. References Crookston, B. M. (2010) Labyrinth Weirs. Dissertation. Utah State University, Logan, Utah. Erpicum, S., Laugier, F., Boillat, J. L., Pirotton, M., Reverchon, B., Schleiss, A. J. (2011) Labyrinth and Piano Key Weirs, International Conference on Labyrinth and Piano Key Weirs (PKW 2011) Erpicum, S., Laugier, F., Pfister, M., Cicero, G. M., Schleiss, A. J. (2013) Labyrinth and Piano Key Weirs II, Second International Workshop on Labyrinth and Piano Key Weirs 2013 Erpicum, S., Laugier, F., Ho Ta Khan, M., Pfister, M. (2017) Labyrinth and Piano Key Weirs III, Third International Workshop on Labyrinth and Piano Key Weirs 2017 Erpicum, S., Archambeau, P., Dewals, B., Pirotton, M. (2017) Hydraulics of Piano Key Weirs: A review. In: Erpicum, Laugier et al. (Hg. ) 2017 – Labyrinth and Piano Key Weirs Lemperiere, F. and Ouamane, A. (2003) The Piano Keys Weir: a new cost-effective solution for spillways, International Journal on Hydropower and Dams. Oertel, M. (2018) Piano Key Weir research: state-of-the-art and future challenges, 7th IAHR International Symposium on Hydraulic Structures, ISHS2018, Aachen, Germany, 475-482, DOI: 10.15142/T3DP9C. Pralong, J., Vermeulen, J., Blancher, B., Laugier, F., Erpicum, S., Machiels, O., Pirotton, M., Boillat, J. L., Leite Ribeiro, M. and Schleiss, A. J. (2011) A naming convention for the Piano Key Weirs geometrical parameters. In: Erpicum, Laugier et al. (Hg. ) 2011 – Labyrinth and Piano Key Weirs. Shen, X., Oertel, M. (2021) Comparative Study of Nonsymmetrical Trapezoidal and Rectangular Piano Key Weirs with Varying Key Width Ratios, Journal of Hydraulic Engineering, 147 (11), https: //doi. org/10.1061/ (ASCE) HY. 1943-7900.0001942. Universite de Liege (2020) World Register of Piano Key weirs prototypes.
Year: 2025