References of "Machiels, Olivier"
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See detailExperimental analysis of PKW hydraulic performance and geometric parameters optimum
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Pirotton, Michel ULg et al

in Proceedings of International workshop on Piano Key Weir for In-stream Storage and Dam Safety - PKWISD-2012 (2012, June 01)

In the scope of dam rehabilitation to manage floods increase or to increase water storage, the Piano Key Weir is a good solution for concrete dams. The efficiency of Piano Key Weirs is now well ... [more ▼]

In the scope of dam rehabilitation to manage floods increase or to increase water storage, the Piano Key Weir is a good solution for concrete dams. The efficiency of Piano Key Weirs is now well demonstrated through various experimental studies. Even if parametrical studies are currently undertaken, the definition of the optimal shape to give to the structure is still missing due to the lack of knowledge in the influence of the large set of geometrical parameters. This paper presents the results of a combine experimental and numerical study of PKW. On the one hand, the study, led on a large scale model of PKW, aims at defining the main parameters influencing the hydraulic behaviour of the structure. On the other hand, the influence of these main parameters has been studied on several scale models considering variation of the weir height, the keys widths and the overhangs lengths. The results of the experiments enable to define optimal values for a common variation of these parameters. [less ▲]

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See detailHydraulic modelling of Piano Key Weirs: a composite approach
Erpicum, Sébastien ULg; Machiels, Olivier ULg; Archambeau, Pierre ULg et al

in Proceedings of International workshop on Piano Key Weir for In-stream Storage and Dam Safety - PKWISD-2012 (2012, May)

During the last few years, several piano key weirs (PKWs) have been built in France and abroad. Thanks to the reduced footprint and high release capacities of this new type of weir, making it particularly ... [more ▼]

During the last few years, several piano key weirs (PKWs) have been built in France and abroad. Thanks to the reduced footprint and high release capacities of this new type of weir, making it particularly suited for concrete dams rehabilitation, lots of other projects in various countries are under construction or study. The prototype use of PKW requires knowledge about its structural behaviour, hydraulic capacities as well as integration into dams’ environment. This paper aims at presenting numerical and physical modelling works performed at the University of Liege to address the last two items. In particular, large scale physical modelling and parametric scale models have enabled to understand the hydraulic behaviour of the structure and to highlight its most influencing geometric parameters as well as their best variation interval depending on various criteria related to the weir design (discharge efficiency, cost…). A 1D numerical model has also been developed based on these experimental investigations. It enables to predict in a few minutes, with 10% accuracy, the discharge capacity of a given PKW geometry within its usual range of operation head. This model, available as a freeware from http://www.pk-weirs.ulg.ac.be, constitutes a key tool for the first design of such weirs. Finally, the scale model studies of major projects such as Raviège dam (France) for Electricité de France - EDF and Ouldjet Mellegue Project (Algeria) for Coyne et Bellier – Tractebel Engineering enable to confront theoretical predictions with experimental results and to address the problem of PKW integration on dam crests. [less ▲]

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See detailNumerical and physical hydraulic modelling of Piano Key Weirs
Erpicum, Sébastien ULg; Machiels, Olivier ULg; Dewals, Benjamin ULg et al

in Proceedings of the 4th Int. Conf. on Water Resources and Renewable Energy Development in Asia (2012, March)

During the last few years, several piano key weirs (PKWs) have been built in France by Electricité de France (EDF). Thanks to the reduced footprint and high release capacities of this new type of weir ... [more ▼]

During the last few years, several piano key weirs (PKWs) have been built in France by Electricité de France (EDF). Thanks to the reduced footprint and high release capacities of this new type of weir, making it particularly suited for concrete dams rehabilitation, lots of other projects in varied countries are under construction or study. The prototype use of PKW requires knowledge about its structural behaviour, hydraulic capacities as well as integration into dams’ environment. This paper aims at presenting numerical and physical modelling works performed at the University of Liege to address the last two points. In particular, large scale physical modelling and parametric scale models enabled to understand the hydraulic behaviour of the structure and to highlight its main geometric parameters as well as their best variation interval depending on various criteria related to the weir design (discharge efficiency, cost…). A 1D numerical model has also been developed based on these experimental investigations. It enables to predict in a few minutes, with 10% accuracy, the discharge capacity of a given PKW geometry on its usual operation head range. This model, available as a freeware on http://www.pk-weirs.ulg.ac.be, constitutes a key tool for the first design of such weirs. Finally, the scale model studies of major projects such as Raviège dam (France) for EDF and Ouldjet Mellegue Project (Algeria) for Coyne et Bellier – Tractebel Engineering enable to confront theoretical predictions with experimental results and to address the problem of PKW integration on dam crests. [less ▲]

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See detailInfluence of the relative alveoli widths on Piano Key Weirs efficiency for varied weir heights
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Proceedings of Int. Symp. on Dams for a changing world (2012)

In the scope of dam rehabilitation to manage floods increase or to increase water storage, the Piano Key Weir is a good solution for concrete dams. Indeed, its labyrinth shape allows discharge capacities ... [more ▼]

In the scope of dam rehabilitation to manage floods increase or to increase water storage, the Piano Key Weir is a good solution for concrete dams. Indeed, its labyrinth shape allows discharge capacities until 4 times more important than traditional ogee-crested weirs and 10 percent more important than labyrinth weirs of same horizontal geometry. Furthermore, the use of up- and downstream overhangs reduces drastically its footprint and enables its use directly on dams crest. The efficiency of Piano Key Weirs is now well demonstrated through various experimental studies. Even if parametrical studies are currently undertaken, the definition of the optimal shape to give to the structure is still missing due to the lack of knowledge in the influence of the large set of geometrical parameters. This paper presents the results of a combine experimental and numerical study about the influence of the relative alveoli widths on the Piano Key Weir discharge capacity. 14 models have been tested providing results for a large range of the inlet to outlet widths ratio and considering variation of the weir height in accordance with former studies. The results of the experiments enable to define optimal values for a common variation of these two parameters. [less ▲]

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See detailExperimental study of the hydraulic behaviour of Piano Key Weirs
Machiels, Olivier ULg

Doctoral thesis (2012)

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See detailOn the Piano Key Weir hydraulics
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Rutschmann, Peter; Grünzner, Markus; Stephan, Hötzl (Eds.) Proceedings of 2nd IAHR Europe Congress (2012)

The Piano Key Weir (PKW) is a kind of labyrinth weir with a geometry that uses overhangs to reduce the base length. The PKW can thus be directly placed on the crest of an existing dam. Together with its ... [more ▼]

The Piano Key Weir (PKW) is a kind of labyrinth weir with a geometry that uses overhangs to reduce the base length. The PKW can thus be directly placed on the crest of an existing dam. Together with its high discharge capacity for low heads (up to four times as high as an ogee-crested weir of same length), this geometric feature makes the PKW an interesting solution for dam rehabilitation and for new dam projects with a high level of constraints (design discharge, available space, reservoir storage, ...). PKW has been initially designed in 2001 and built for the first time in 2006 by “Electricité de France (EDF)”. Even if the first experimental studies confirmed its appealing discharge capacities, the flow upstream, over and downstream of this complex structure is still poorly described. Following a 3 years intensive experimental and numerical study of PKW hydraulics, the paper presents a general description of the hydraulic behavior of the PKW. It aims to explain the influence of the large set of geometric parameters on the discharge capacity. The assumptions of the study link various phenomenons depicted in the literature about PKW and an evaluation of their relative influence on the PKW efficiency is given. The role of the crests shape, the crests submersion, the nappes interactions, the crests approach conditions, the position of the control section and the head losses are analyzed. Design advices are also given. [less ▲]

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See detailInfluence of weir height and keys slope on PKW discharge
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Proceedings of 4th IAHR International Symposium on Hydraulic Structures (2012)

Piano Key Weir is a cost effective solution for rehabilitation as well as for new dam projects with a high level of constraints (limited space, high specific flood discharge, small reservoir level ... [more ▼]

Piano Key Weir is a cost effective solution for rehabilitation as well as for new dam projects with a high level of constraints (limited space, high specific flood discharge, small reservoir level variation). While the higher efficiency of the Piano Key Weir compared to standard linear weirs has already been demonstrated, its optimal geometry is still poorly defined. Even if former studies highlighted the main influence of the weir height on its discharge capacity, the distinction between weir height effect and keys slope one is not so straight forward. In order to distinguish the influence of these two parameters, the use of parapet walls has been tested to increase weir height keeping bottom slope constant, and to decrease keys slope keeping the weir height constant. The experimental results presented in this paper enable to distinguish the relative influences of the keys bottom slope and of the weir height on the Piano Key Weir release capacity. Comparisons with former experimental results as well as design guidelines are also provided. [less ▲]

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See detailMethod for the preliminary design of Piano Key Weirs
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Houille Blanche (2012), 4

The Piano Key Weir (PKW) is a particular geometry of weir associating to a labyrinth shape the use of overhangs to reduce the basis length. The PKW could thus be directly placed on a dam crest. Together ... [more ▼]

The Piano Key Weir (PKW) is a particular geometry of weir associating to a labyrinth shape the use of overhangs to reduce the basis length. The PKW could thus be directly placed on a dam crest. Together with its important discharge capacity for low heads, this geometric feature makes the PKW an interesting solution for dam rehabilitation. However, its hydraulic design remains problematic, even at a preliminary stage. This paper presents a preliminary design method based on results of experimental tests. The method enables to design project models by extrapolation of characteristics of existing idealized scale models. A practical application is presented to illustrate the method. [less ▲]

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See detailEtudes paramétriques expérimentales réalisées à l’Université de Liège
Machiels, Olivier ULg

Conference (2011, December 02)

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See detailExperimental observation of flow characteristics over a Piano Key Weir
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

in Journal of Hydraulic Research (2011), 49(3), 359-366

The Piano Key Weir is a type of labyrinth weir using overhangs to reduce the foot print of the foundation. These are directly placed on a dam crest. Together with its high discharge capacity for low heads ... [more ▼]

The Piano Key Weir is a type of labyrinth weir using overhangs to reduce the foot print of the foundation. These are directly placed on a dam crest. Together with its high discharge capacity for low heads, this geometry makes these weirs interesting for dam rehabilitation. However, the Piano Key Weir is a new weir type, firstly designed in 2001 and built from 2006 by Electricité de France. Even if experimental studies confirmed its appealing discharge capacities, the flow upstream, over and downstream of this complex structure is still not well known. This research presents experimental test results performed on a 1:10 scale model. The experiments aim at determining the flow features along the weir depending on the upstream head. The flow conditions are characterized in terms of specific discharge, velocity, pressure, water level and streamlines along the weir. [less ▲]

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See detailTheoretical and numerical analysis of the influence of the bottom friction formulation in free surface flow modelling
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Water S A (2011), 37(2),

Bottom friction modeling is an important step in river flows computation with 1D or 2D solvers. It is usually performed using energy slope based formulations established for uniform flow conditions or a ... [more ▼]

Bottom friction modeling is an important step in river flows computation with 1D or 2D solvers. It is usually performed using energy slope based formulations established for uniform flow conditions or a turbulent regime based approach relying on turbulence analysis. However, the use of these formulations is often done for relative roughness far from their validity fields. Furthermore, the theoretical definition of the roughness coefficients, defined by the different authors of both approaches, is no more available for usual numerical flow modeling, considering numerical approximations. The value of this coefficient becomes generally dependent of the flow conditions. Following the definition of the flow validity field of the main friction formulations proposed in literature, an original formulation has been developed. It combines two explicit turbulent regime based formulations smoothly linked by a polynomial expression, providing a continuous formulation on the wide range of roughness usually encountered in river flows. The formulation is suitable to model, with a unique value of the friction coefficient, river flows with a wide range of hydrodynamic properties (water depth, discharge). The efficiency of this new formulation, fitted on explicit friction formulations and numerically adjusted, is demonstrated through various 1D and 2D practical applications. [less ▲]

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See detail1D numerical modeling of the flow over a Piano Key Weir
Erpicum, Sébastien ULg; Machiels, Olivier ULg; Archambeau, Pierre ULg et al

in Erpicum, Sébastien; Laugier, Frédéric; Boillat, Jean Louis (Eds.) et al Labyrinth and Piano Key Weirs - PKW 2011 (2011)

Because of the PK-Weir geometric specificities, its hydraulic capacity remains difficult to predict without using experimental techniques. A 1D numerical model of the flow over a PK-Weir has been ... [more ▼]

Because of the PK-Weir geometric specificities, its hydraulic capacity remains difficult to predict without using experimental techniques. A 1D numerical model of the flow over a PK-Weir has been developed at the Research unit HACH at the University of Liege. It is based on a 1D modeling of the inlet and the outlet separately, with a single upstream reservoir and interactions between both flows by exchange of mass and momentum along the lateral crest. The comparison of the numerical results with various experimental data showed the ability of the numerical model to predict with reasonable accuracy the release capacity of a PK-Weir, whatever its geometry. The tests of the solver enable to highlight the significant influence of the inlet and outlet width on the weir release capacity. They also suggest that improvements of the numerical model may lie in the evaluation of the discharge coefficient of the lateral crest. [less ▲]

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See detailInfluence of the alveoli slopes on the discharge capacity of Piano Key Weirs
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Proceedings of the 34th IAHR world congress (2011)

Piano Key Weir is a cost effective solution for rehabilitation as well as for new dam project with a high level of constraints (space, flood discharge, reservoir level).If the efficiency of the Piano Key ... [more ▼]

Piano Key Weir is a cost effective solution for rehabilitation as well as for new dam project with a high level of constraints (space, flood discharge, reservoir level).If the efficiency of the Piano Key Weir has already been well demonstrated, the definition of its optimal geometry has been still poorly approached. In order to improve the design of the complex geometry of this structure, the study of the influence of the mean geometrical parameters on the discharge capacity is an essential stage. Following a former experimental study of the flow over Piano Key Weirs, highlighting the mean influence of three geometrical parameters, this paper presents the results of an experimental parametric study. These results highlight the influence of the alveoli bottom slopes on the Piano Key Weir release capacity. Comparisons with numerical and analytical results, as well as design advices are also provided. [less ▲]

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See detailVarying the alveoli slopes of Piano key Weirs: Interests and limitations
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Pina, C.; Portela, E.; Gomes, J. (Eds.) Proceedings of the 6th International conference on dam engineering (2011)

Piano Key Weir is a cost effective solution for rehabilitation as well as for new dam project with a high level of constraints (space, flood discharge, reservoir level). Its labyrinth shape permits the ... [more ▼]

Piano Key Weir is a cost effective solution for rehabilitation as well as for new dam project with a high level of constraints (space, flood discharge, reservoir level). Its labyrinth shape permits the evacuation of discharges till four times more important than ogee-crested weirs with the same length at the dam crest, when the use of overhangs permits the building of the auto-equilibrated structure directly on dam crest. If the efficiency of the Piano Key Weir has already been well demonstrated, the definition of its optimal geometry has been still poorly approached. In order to improve the design of the complex geometry of this structure, the study of the influence of the mean geometrical parameters on the discharge capacity is an essential stage. Following a former experimental study of the flow over Piano Key Weirs, highlighting the mean influence of three geometrical parameters, this paper presents the results of an experimental parametric study. These results highlight the influence of the alveoli bottom slopes on the Piano Key Weir release capacity. In this paper, the interests and limitations of the variation of the slopes are explained. Recommendations directly linked to the observation of the experimental models are also provided to improve the design of PKW. [less ▲]

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See detailEnergy dissipation on a stepped spillway downstream of a Piano Key Weir - Experimental study
Erpicum, Sébastien ULg; Daux, Christophe; Machiels, Olivier ULg et al

in Erpicum, Sébastien; Laugier, Frederic; Boillat, Jean Louis (Eds.) et al Labyrinth and Piano Key Weirs - PKW 2011 (2011)

Piano Key Weir (PKW) is a new type of weir showing appealing hydraulic capacities. Its specific geometric features create different interacting flows and jets downstream of the structure. This suggests ... [more ▼]

Piano Key Weir (PKW) is a new type of weir showing appealing hydraulic capacities. Its specific geometric features create different interacting flows and jets downstream of the structure. This suggests that the use of a PKW to control the flow upstream of a stepped spillway may help in enhancing energy dissipation on the downstream channel. The first results of an experimental study carried out at the Laboratory of Engineering Hydraulics – HACH in the scope of a Coyne & Bellier – Tractebel Engineering project are presented in the paper. The goal of the study was to compare the energy dissipation on a stepped spillway downstream of a PKW with the one which takes place on the same spillway equipped with a standard ogee-crested weir. Despite similar global energy dissipation rates whatever the weir type due to the relative important height of the spillway, significant differences in the aeration of the flow along the spillway have been shown. This paves the way to further investigations. [less ▲]

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See detailPiano Key Weir preliminary design method – Application to a new dam project
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Erpicum, Sébastien; Laugier, Frederic; Boillat, Jean Louis (Eds.) et al Labyrinth and Piano Key Weirs - PKW 2011 (2011)

Within the framework of development of PKW use for rehabilitation as well as for new dam projects, the development of efficient design methods is essential. Currently, the design of PKW projects is done ... [more ▼]

Within the framework of development of PKW use for rehabilitation as well as for new dam projects, the development of efficient design methods is essential. Currently, the design of PKW projects is done by mean of scale modeling, on the basis of a geometry initially designed based on the general knowledge issued from idealized experimental studies and former PKW buildings. This paper presents a systematic method for PKW preliminary design. The method is based on extrapolation of existing experimental results to develop one or several available project designs, regarding the project constraints (discharge, reservoir levels, available space, …). The model permits then the optimization of the design depending on technical and economical interests (increase of the safety, decrease of the maximal head, limiting the weir dimensions, limiting construction costs, …). The application of the method to a new large dam project is presented, highlighting the interest of the method for the optimization of the design depending on technical and economical interests. [less ▲]

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See detailInfluence of the PKW height on its discharge capacity
Machiels, Olivier ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Erpicum, Sébastien; Laugier, Frédéric; Boillat, Jean Louis (Eds.) et al Labyrinth and Piano Key Weirs - PKW 2011 (2011)

Within the framework of Piano Key Weir (PKW) development, the hydraulic optimization of its geometry seems essential. First systematic studies of all the geometrical parameters of the PKW highlight a more ... [more ▼]

Within the framework of Piano Key Weir (PKW) development, the hydraulic optimization of its geometry seems essential. First systematic studies of all the geometrical parameters of the PKW highlight a more important influence of some parameters compared to other ones. A former study led, at the University of Liege, on a large scale model of PKW highlights the main influence of the inlet cross section on the global discharge capacity of the weir. Based on this finding, the geometrical parameters influencing the inlet cross section seem to be the most influential parameters of the weir efficiency. This paper presents results of an experimental study using models of PKW with varying height. The mean non-dimensional parameters characterizing the geometry of the models are maintained constant, only varying the slope of the alveoli. The results of the 7 models studied, with a wide range of slopes (height over length) from 0.25 to 1.5, are presented. Based on these results, an analytical formulation of the unit discharge over a PKW as a function of its height is developed. [less ▲]

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See detailWOLF 1D PKW - 1D numerical model of the flow over a piano key weir
Erpicum, Sébastien ULg; Archambeau, Pierre ULg; Dewals, Benjamin ULg et al

Software (2011)

The Piano Key Weir (PKW) is a new type of free weir, similar to a labyrinth weir, showing appealing performance to release high discharges under limited head levels in the upstream reservoir. Because of ... [more ▼]

The Piano Key Weir (PKW) is a new type of free weir, similar to a labyrinth weir, showing appealing performance to release high discharges under limited head levels in the upstream reservoir. Because of the PKW geometric specificities, its hydraulic capacity remains difficult to predict without using experimental techniques. Wolf1D PKW numerical model has been developed at the Research Unit HACH at the University of Liege to model the flow over a PKW. It is based on a 1D modelling of the PKW main elements separately (the inlet and the outlet), with a single upstream reservoir and interactions between both flows by exchange of mass and momentum along the lateral crest. [less ▲]

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See detailA naming convention for the Piano Key Weirs geometrical parameters
Pralong, Julien; Vermeulen, Julien; Blancher, Benoit et al

in Erpicum, Sébastien; Laugier, Frédérique; Boillat, Jean-Louis (Eds.) et al Labyrinth and Piano Key Weirs - PKW 2011 (2011)

Flood management is more than ever an issue for dam designers and engineering consulting firms in charge of rehabilitation works. Piano Key Weirs are a new cost-effective type of spillway designed to ... [more ▼]

Flood management is more than ever an issue for dam designers and engineering consulting firms in charge of rehabilitation works. Piano Key Weirs are a new cost-effective type of spillway designed to improve dams discharge capacity. These structures are particularly attractive: they can easily be built on existing structures and enable very high discharge capacities. Therefore, Piano Key Weirs are nowadays studied worldwide. Piano Key Weir description involves a lot of geometrical parameters (more than 30), which designations are not already universally defined. A naming convention is required to enhance exchanges and cooperation between the numerous developers. A naming convention has been developed at EDF – Hydro Engineering Center in cooperation with the Laboratory of Hydraulic Constructions (LCH), Ecole Polytechnique Fédérale de Lausanne and the Laboratory of Hydrology, Applied Hydrodynamics and Hydraulic Constructions (HACH), University of Liege. This paper describes the proposed naming convention and gives definitions and notations of the various geometrical parameters. This work represents a first attempt which should be updated with the contribution of stakeholders involved in this topic. [less ▲]

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