References of "Lodomez, Maurine"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailMitigation Techniques for Nappe Oscillations on Free-Overfall Structures
Lodomez, Maurine ULiege; Crookston, Brian ULiege; Tullis, Blake et al

in Civil Engineering ASCE (in press)

Nappe oscillation is a phenomenon that can have an undesirable impact to the local environmental (e.g., nearby residences, parks) as the phenomenon has been observed to produce a significant level of ... [more ▼]

Nappe oscillation is a phenomenon that can have an undesirable impact to the local environmental (e.g., nearby residences, parks) as the phenomenon has been observed to produce a significant level of noise caused by acoustic pressure waves. As a result, a detailed investigation was undertaken to identify practical and effective mitigation solutions to address these effects for free-overfall structures. Nappe oscillations were studied using a prototype-scale linear weir (weir length of 3.5 m and fall height of 3 m), a high-speed camera, and audio equipment. The effectiveness of various crest modifications to reduce nappe oscillation and any corresponding impacts to hydraulic efficiency were evaluated. The test matrix included the optimization (position and spacing of elements) of three mitigation solutions: 12 configurations with projecting elements, 5 configurations with deflectors and one configuration with a step. These three countermeasures proved to be effective after the optimization of their characteristics. In particular, deflectors or a step produced the maximum noise reduction while decreasing the discharge coefficient by less than 3 % over the range of experimental conditions. [less ▲]

Detailed reference viewed: 33 (4 ULiège)
Full Text
See detailData requirements for computational modelling at the network level
Dewals, Benjamin ULiege; Erpicum, Sébastien ULiege; Pirotton, Michel ULiege et al

E-print/Working paper (2019)

Detailed reference viewed: 19 (6 ULiège)
See detailExperimental Study of Nappe Oscillations on Free Overfall Structures
Lodomez, Maurine ULiege

Doctoral thesis (2019)

Free-overfall structures such as weirs and crest gates are commonly used as control structures for a variety of applications including irrigation, water treatmentand dam safety. The gravity-driven free ... [more ▼]

Free-overfall structures such as weirs and crest gates are commonly used as control structures for a variety of applications including irrigation, water treatmentand dam safety. The gravity-driven free falling jet on the downstream side of these structures, called the nappe, may display a variety of behaviors and instabilities among which, under relatively low heads/discharges, nappe oscillations, also known as nappe vibrations. This oscillating phenomenon is characterized by oscillations of the thin flow nappe cascading downstream of the crest and results in a significant disturbing noise production that increases negatively the environmental and societal impacts of the hydraulic structure. Given the lack of quantitative information reported in literature and the inchoate understanding of the dominant processes underpinning nappe oscillations occurrence and development, the global objective of this PhD thesis was to improve the knowledge of the nappe oscillation phenomenon. To that end, experimental modelling was seen as the best way to analyse the problem. First, a prototype scale model of a linear weir has been specifically designed and made flexible with respect to the main parameters of the weir. Then, two original characterization methods of the nappe oscillations properties have been developed based on the distinct audio and visual traits of the phenomenon. The application of these methods allowed the determination of the occurrence and development of the oscillations and their associated frequencies. Both were used systematically to assess the influence of various hydraulic and geometric parameters on the nappe oscillation phenomenon. Secondly, given the importance of scale physical modelling for hydraulic structure design, the possible scale effects affecting nappe oscillation were studied by considering a 1:3 scale model of the aforementioned prototype scale facility. The operation of this second model showed that nappe oscillations cannot be scaled according to the traditional similitude for weirs (Froude similitude). Instead, they always occur within the same unit discharge range independent of size scale, although they are prone to hysteretic behaviour and are less stable over time for smaller weir dimensions. Third, considering the data collected from the study of 52 geometric configurations and the expertise gained from hours of nappe oscillation observations and analysis, necessary conditions for nappe oscillation occurrence have been defined. Along with geometrical criteria regarding the fall height and width of the structure, these conditions, although not sufficient, allow to predict the occurrence of the oscillation in many cases. Finally, original mitigation techniques have been developed with the help of practicing engineers and contractors. Identified with respect to constructability, durability, performance and maintenance, these solutions were tested and optimized regarding disturbing noise reduction without impacting the hydraulic efficiency of the structure. Beside these extensive experimental works, in-situ measurements at two Belgian dams proved the applicability and robustness of the measurement methodologies developed in the framework of this thesis and the utility of the results to solve real world problems. [less ▲]

Detailed reference viewed: 14 (4 ULiège)
Full Text
Peer Reviewed
See detailCould Piano key weirs be subject to nappe oscillations?
Lodomez, Maurine ULiege; Pirotton, Michel ULiege; Dewals, Benjamin ULiege et al

in 3rd International Workshop on Labyrinth and Piano Key Weirs - PKW 2017 (2017)

Nappe oscillation may affect a variety of free overflow hydraulic structures operating at low heads such as crest gates and various types of weirs. This phenomenon produces oscillations in the thin nappe ... [more ▼]

Nappe oscillation may affect a variety of free overflow hydraulic structures operating at low heads such as crest gates and various types of weirs. This phenomenon produces oscillations in the thin nappe cascading downstream of the control structure. These oscillations can result in a high noise levels that may affect people and structures located nearby. With long linear and thin overtopping walls, piano key weirs might be subject to strong nappe oscillation risks, as a few documented cases with labyrinth weirs. However, the specific geometric features of piano key weirs, such as the outlet ramps or the limited width of the inlet apex, could perhaps prevent the development of nappe oscillation. In this paper, a prototype-scale linear weir is operated to assess the risk of nappe oscillations on a piano key weir like configuration (sidewall). In particular, the effect of the weir width and inclined apron is analyzed. The experimental results show that nappe oscillation development should not occur on piano key weir, contrary to what might be observed on a labyrinth weir with the same crest. [less ▲]

Detailed reference viewed: 77 (13 ULiège)
Full Text
Peer Reviewed
See detailNappe Vibration Mitigation Techniques for Free-overfall Structrures
Lodomez, Maurine ULiege; Crookston, Brian M.; Tullis, Blake P. et al

in Full Proceedings: Hydraulic Structures and Water System Management (2016, June 27)

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 ... [more ▼]

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. [less ▲]

Detailed reference viewed: 39 (11 ULiège)
Full Text
Peer Reviewed
See detailScale effects in physical piano key weirs models
Erpicum, Sébastien ULiege; Tullis, Blake; Lodomez, Maurine ULiege et al

in Journal of Hydraulic Research (2016), 54(6), 692-698

With inertia and gravity representing the dominant forces for most open channel flow applications (e.g. weir flow), Froude similitude is commonly used for scaling hydraulic performance data from the model ... [more ▼]

With inertia and gravity representing the dominant forces for most open channel flow applications (e.g. weir flow), Froude similitude is commonly used for scaling hydraulic performance data from the model to prototype structures. With weir flow, as the upstream head decreases, however, the relevance of surface tension and viscosity forces can increase to the point when the model and prototype similitude is not fully achieved through Froude scaling. Such discrepancies are referred as size-scale effects, and among other things, can result in variations in the head–discharge relationship, nappe trajectory, and air entrainment. Published criteria for avoiding significant size-scale effects for free flow over linear weirs have suggested that minimal heads of ∼0.02 to 0.07m be respected, independently of the model size. In this study, the size-scale effect, minimum upstream head, and Weber number limits are investigated for four piano key weirs with geometric model scales of 1:1, 1:7, 1:15, and 1:25. [less ▲]

Detailed reference viewed: 52 (10 ULiège)
Peer Reviewed
See detailCharacterization of Nappe Vibration on a Weir
Lodomez, Maurine ULiege; Pirotton, Michel ULiege; Dewals, Benjamin ULiege et al

in Sustainable Hydraulics in the Era of Global Change (2016)

The nappe vibration phenomenon may affect numerous prototype structures, such as gates and spillways, when they operate under low head conditions. This phenomenon, which is far not well understood and ... [more ▼]

The nappe vibration phenomenon may affect numerous prototype structures, such as gates and spillways, when they operate under low head conditions. This phenomenon, which is far not well understood and poorly controlled, produces frequency oscillations in the thin flow nappe cascading downstream of the weir. These oscillations result in a disturbing noise production that increases the environmental and societal impacts of the hydraulic structure. Given limited information available regarding the physical processes of this phenomenon, a detailed investigation has been undertaken to characterize the flow for free-overfall structures where nappe vibration may be of concern. The research conducted on a prototype-scale linear weir model (weir length of 3.5 m and a fall height of 3 m) at the Engineering Hydraulics laboratory of the University of Liège enable to describe the flow and nappe vibration by using image and sound analysis. The paper presents the first quantitative results of the study. [less ▲]

Detailed reference viewed: 89 (14 ULiège)
Full Text
Peer Reviewed
See detailFrequencies of Nappe Vibration for Free-overfall Structures
Lodomez, Maurine ULiege; Pirotton, Michel ULiege; Dewals, Benjamin ULiege et al

in 6th IAHR IJREWHS (2016)

Under relatively low-head discharges, the occurrence of nappe oscillation, otherwise known as nappe vibration, may be observed on hydraulic structures with a free overfall, such as weirs, crest gates and ... [more ▼]

Under relatively low-head discharges, the occurrence of nappe oscillation, otherwise known as nappe vibration, may be observed on hydraulic structures with a free overfall, such as weirs, crest gates and fountains. This phenomenon, which has been early identified as undesirable and potentially dangerous on gates, is characterized by oscillations in the thin flow nappe cascading downstream of the crest. In addition, these oscillations produce a significant level of noise and acoustic pressure waves that increase the environmental and societal impacts of the structure. A review of the scientific literature shows a lack of consensus regarding the causes and source of the oscillations development. In this context of relatively poor understanding of the dominant processes, a detailed investigation has been undertaken to identify and quantify the nappe vibration mechanism. The research is being performed with a prototype-scale linear weir located at the Engineering Hydraulics laboratory of the University of Liège. The study employs high-speed cameras and audio equipment to characterize the nappe vibration. This paper presents first characteristics of the nappe vibrations gained from images and sound analysis, especially in terms of vibration frequency, for a quarter round and a half round weir crest. This study shows that frequencies measured by sound and image analyses are identical and depend on the crest shape, the fall height and the unit discharge. [less ▲]

Detailed reference viewed: 44 (7 ULiège)
Full Text
Peer Reviewed
See detailPhysical modeling of an aerating stepped spillway
Erpicum, Sébastien ULiege; Lodomez, Maurine ULiege; Savatier, Jérémy et al

in Crookston, Brian; Tullis, Blake (Eds.) Hydraulic Structures and Water System Management (2016)

To mitigate the negative effects on the water quality in the downstream river of a projected large dam, and in particular to increase the dissolved oxygen concentration during low flow periods within the ... [more ▼]

To mitigate the negative effects on the water quality in the downstream river of a projected large dam, and in particular to increase the dissolved oxygen concentration during low flow periods within the first 10 years of dam operation, an aerating weir has been designed and tested on a physical model at the Laboratory of Engineering Hydraulics (HECE) of the Liege University. The design of the structure has been done considering data from the literature. The selected solution is a 3 m high stepped spillway designed to operate in nappe flow conditions within the range of design discharges (25 – 100 m³/s). To validate the design, a physical model representing a section of the weir at a 1:1 scale has been built and operated in the laboratory. Chemical dissolved oxygen removal technique has been applied upstream of the model to be able to measure the weir aerating efficiency. The physical model results show that the proposed structure is able to maintain, in the range of discharge in the river from 25 to 100 m³/s, a minimum 5 mg/l oxygen concentration downstream, whatever the upstream oxygen concentration. The paper presents the design process of the weir, the scale model features and the results of the validation tests on the physical model. The prototype construction will take place in 2017 and the water quality will be monitored. [less ▲]

Detailed reference viewed: 23 (5 ULiège)
Full Text
Peer Reviewed
See detailComparison between Experimental and SPH Models over a Sharp-crested Weir
Lodomez, Maurine ULiege; Erpicum, Sébastien ULiege; Dewals, Benjamin ULiege et al

in 5th IAHR International Junior Researcher and Engineer Workshop on Hydraulic Structure (2014, August 28)

In this paper the numerical simulations of a free surface flow over a sharp-crested weir are presented and compared to experimental results. The numerical model implemented consists of the meshless ... [more ▼]

In this paper the numerical simulations of a free surface flow over a sharp-crested weir are presented and compared to experimental results. The numerical model implemented consists of the meshless Smoothed Particle Hydrodynamics (SPH) method which uses Navier-Stokes equations and the Tait equation of state for water. This numerical method has been developed in the framework of a master thesis and aimed to define the characteristics of the free jet. The validation of the results was performed through the analysis of the pressure field and the comparison of the numerical free surface profiles with experimental measurements conducted in the Hydraulic Laboratory of the University of Liège (ULg). A good qualitative agreement has been obtained. [less ▲]

Detailed reference viewed: 55 (21 ULiège)
Full Text
See detailDetermining the characteristics of a free jet in 2-D by the SPH method
Lodomez, Maurine ULiege

Master's dissertation (2014)

The Smoothed Particle Hydrodynamic method is a numerical method developed in 1977 to solve astrophysical problems. This numerical method is meshless, particle and Lagrangian and has been adapted to ... [more ▼]

The Smoothed Particle Hydrodynamic method is a numerical method developed in 1977 to solve astrophysical problems. This numerical method is meshless, particle and Lagrangian and has been adapted to hydraulic field. In this master’s thesis, the method is positioned relative to the classical numerical methods. The SPH formalism and its adaptation to hydraulic domain is exposed. The basics of SPH formalism are firstly the integral representation of a function and its derivative and secondly the particle approximation. The application of the SPH method to hydraulic domain is made by writting Navier Stokes equations in Lagrangian and SPH formalisms. Then, the specificities implemented in the code are tackled. These specificities are the state equation, the viscosity, the boundary conditions, the neighbors search and the problem initialization. Afterward, a modification of the initial didactic program, usable for constant domain in 3D, is performed. The changes are embodied to enable both 2D and 3D simulations with particle inflows and outflows. The validation of this modified code is performed thanks to four test cases. These test cases permit to validate the code and highlight the limitations of the method implemented such as kernel and the viscosity choices. Finally flows over sharped-crest weir have been simulated. These simulations were compared to results from the literature and experimental tests performed in the hydraulic laboratory. If some improvements are possible, such as injection and initialization of incoming particles, the results of these simulations show that the overall behavior of the free-jet is depicted. Indeed, the simulated jet admits a profile close to the experimental profiles. [less ▲]

Detailed reference viewed: 28 (8 ULiège)