A Performance Comparison of Machine Learning Algorithms for Arced Labyrinth Spillways

Labyrinth weirs provide an economic option for flow control structures in a variety of applications, including as spillways at dams. The cycles of labyrinth weirs are typically placed in a linear configuration. However, numerous projects place labyrinth cycles along an arc to take advantage of reservoir conditions and dam alignment, and to reduce construction costs such as narrowing the spillway chute. Practitioners must optimize more than 10 geometric variables when developing a head–discharge relationship. This is typically done using the following tools: empirical relationships, numerical modeling, and physical modeling. This study applied a new tool, machine learning, to the analysis of the geometrically complex arced labyrinth weirs. In this work, both neural networks (NN) and random forests (RF) were employed to estimate the discharge coefficient for this specific type of weir with the results of physical modeling experiments used for training. Machine learning results are critiqued in terms of accuracy, robustness, interpolation, applicability, and new insights into the hydraulic performance of arced labyrinth weirs. Results demonstrate that NN and RF algorithms can be used as a unique expression for curve fitting, although neural networks outperformed random forest when interpolating among the tested geometries

Energy Dissipation of Type a Piano Key Weirs

A Piano Key weir (PK weir) is a nonlinear, labyrinth-type weir well suited for rehabilitation projects due to a relatively small footprint and the ability to pass large discharges for lesser upstream-head values when compared with other weir types. A critical component of a hydraulic structure is the energy-dissipative properties. Currently, information and guidance is limited, with previous energy dissipation studies of PK weirs primarily of specific projects. Therefore, to document and quantify energy dissipation, four laboratory-scale Type A PK weir models with different width ratios (Wi/Wo) were studied, with 255 tests comprising this new dataset, along with detailed observations of the flow field. Results were compared to existing published data regarding energy dissipation downstream of trapezoidal and rectangular labyrinth weirs. To support design efforts, two equations, both functions of head-water ratio (H/P) and Wi/Wo, are proposed to predict the relative residual energy downstream of PK weirs. The energy dissipation of PK weirs is largest at low flows and decreases in a logarithmic-like manner as flow increases. PK weirs with increased hydraulic efficiency, caused by an increase in Wi/Wo, resulted in slightly smaller energy dissipation values within the range 0.2 ≤ H/P ≤ 0.8. The energy dissipation of PK weirs was found to be relatively constant, independent of Wi/Wo, and in the ranges 0.07 ≤ H/P ≤ 0.2 and 0.8 ≤ H/P ≤ 0.95

Evolution of local scour downstream of Type A PK weir in non-cohesive sediments

Abstract A large-scale piano key weir laboratory study was conducted to investigate the evolution of the scour process occurring in the downstream basin for two non-cohesive granular bed materials, including the analysis of scour-hole geometry and patterns at equilibrium. It was observed that hydraulic conditions, particularly tailwater level, significantly affect the scour mechanisms and equilibrium morphology, eventually resulting in scour depths that exceeded the weir height. Unprecedented insights on the scour dynamics are also provided, along with tools to estimate the time evolution and maximum scour depth, its location in the streamwise direction, and the maximum scour length

Nappe Vibration Mitigation Techniques for Free-overfall Structures

Nappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow hydraulic structures operating at low heads, such as fountains, crest gates, and weirs. This phenomenon is visually characterized by oscillations in the thin nappe cascading downstream of the control structure. These oscillations can produce a significant level of noise and acoustic pressure waves, which can increase the environmental and societal impacts of the hydraulic structure. As a result, a detailed investigation has been undertaken to identify practical and effective mitigation solutions for free-overfall structures where nappe vibration may be of concern. Research is being performed with a prototype-scale linear weir (weir length of 3.5 m and fall height of 3 m) located at the Engineering Hydraulics laboratory of the University of Liège, to assess the effectiveness of various crest modifications and any corresponding impacts to hydraulic efficiency (i.e., flow rate). The test matrix includes the optimization (position and spacing of elements) of three mitigation solutions which are projecting bolts, deflectors and step. In addition, a high-speed camera and audio equipment have been used to evaluate effectiveness of the configurations in reducing nappe vibration. Finally, this practical study has identified countermeasures suitable for retrofits and new construction, easy to construct, durable, hydraulically efficient, and with minimal potential for debris collection

Staged and Notched Labyrinth Weir Hydraulics

ABSTRACT: Replacement spillways are frequently required to pass revised and larger design storm events. Generally matching the outflow hydrograph of the existing spillway is also a common design requirement. Labyrinth spillways can increase spillway discharge capacity. Staged and notched sections of crest have been used in design to satisfy discharge hydrograph requirements. However, inadequate hydraulic design information is available specific to staged and notched labyrinth weirs. In this study, the flow characteristics of multiple staged and notched labyrinth weir configurations (laboratory-scale) were tested. Head-discharge relationships were evaluated experimentally and compared with computed results using superposition (predicting the discharge over the upper and lower stages separately and summing). The results of this comparison show that, for all configurations tested, the superposition technique estimated actual discharges by approximately ±10%

Hydraulic Structure Collaborations: Mind the Gap of Industry and Academia

Hydraulic structures are the common element to many water challenges. Seeking sustainable solutions requires wise decision making and effective stewardship. As we pursue these two goals, we have a constant opportunity for collaboration as both individuals and groups or communities. Indeed, operative collaborations across business, education, research institutions have leveraged the knowledge and experience of each and resulted in innovative, practical, and cost-effective water solutions. This keynote focuses on the commonality between industry and academia via the experiences and viewpoints of the author specific to hydraulic structures, including 1) the value of applied research and project collaborations, 2) the flow of information between practitioners and researchers, 3) design-focused education and knowledge, and 4) curriculum suggestions for young faculty. This talk will also give a perspective of the future that may be of interest to those navigating the gap between your University education and your first employment and your first years as a young professional

Book review: Hydraulic engineering of dams

peer reviewe

Hydraulic Structures and Water System Management-ISHS2016 in Perspective

Hydraulic structures are vital features in our water infrastructure, as they help meet the diverse and challenging demands of society, including conveyance, flood protection, environmental and ecological impacts, and systems management. Indeed, there are a number of challenges facing engineers today. This 6th IAHR International Symposium on Hydraulic Structures (ISHS2016) brought together domestic and international expertise from research, practice, and implementation in a forum for knowledge exchange and networking discussion on critical issues related to hydraulic structure research, performance, operations, maintenance, and community implications. It continued the rich tradition of this series by stimulating interest on advancement in the development and use of hydraulic structure elements and systems. Presentations and discussions were held on advanced tools, applications, and unique approaches needed to develop and implement more effective, environmentally sound, and robust solutions. It is believed that the proceedings of ISHS2016 provide applicable state-of-the-art expertise in hydraulic structure analysis and design to the engineering profession