Parapet wall effect on Piano Key Weirs efficiency

in Journal of Irrigation & Drainage Engineering (2013), 139(6), 506-511

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. In order to improve the design of the complex geometry of this structure, the use of parapet walls has been tested. They consist of vertical extensions placed over the weir crest. Following a former study of the influence of the weir height on its discharge capacity, this paper presents the results of an experimental campaign dedicated to investigating the effect of parapet walls to increase weir height while reducing bottom slopes and keeping the weir height constant. These results indicate the relative influences of the alveoli bottom slopes 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 ▲]

Modélisation numérique hydrosédimentaire au service de la gestion durable des sédiments

in Recyclage et Valorisation (2013), 41

La gestion des sédiments revêt une importance croissante pour l’exploitation des voies navigables et nombre de projets de construction de barrages et de complexes hydroélectriques. L’impact des apports en ... [more ▼]

La gestion des sédiments revêt une importance croissante pour l’exploitation des voies navigables et nombre de projets de construction de barrages et de complexes hydroélectriques. L’impact des apports en matériaux solides se manifeste tant par des effets à long terme, telle la réduction de la capacité du réservoir, que par des conséquences à plus court terme, telle l’usure prématurée des turbines. L’étude détaillée des effets sédimentaires s’impose donc de plus en plus tôt dans la conception de nouveaux aménagements. Elle est aussi un objectif tout au long de l’exploitation des ouvrages, dans une perspective de gestion sécuritaire et durable. [less ▲]

Scientific basis for transnational flood management in the Meuse basin

Conference (2013, March 22)

Evolution du risque lié aux inondations de la Meuse : Influences relatives du climat et de la croissance des zones résidentielles

Scientific conference (2013, February 28)

Chaque année, les inondations par débordement des rivières provoquent des dommages significatifs en Wallonie. L’ampleur de ceux-ci est liée à l’importance des crues elles-mêmes, mais aussi à l’occupation ... [more ▼]

Chaque année, les inondations par débordement des rivières provoquent des dommages significatifs en Wallonie. L’ampleur de ceux-ci est liée à l’importance des crues elles-mêmes, mais aussi à l’occupation du sol des terrains inondés. Dans le contexte des changements climatiques, comment évolueront les débits des crues « extrêmes » ? Quelle pourrait être l’influence de l’évolution de l’occupation du sol sur les dommages ? La vallée de la Meuse a été choisie pour investiguer et concrétiser les réponses à ces questions. Les dommages liés à une crue centennale ont été calculés pour la situation actuelle ainsi que pour différentes situations potentielles en 2100, suivant un scénario d’évolution climatique et neuf scénarios d’urbanisation de la Wallonie. L'accent sera mis sur tant sur le développement de ces scénarios que sur les conclusions robustes tirées des résultats obtenus en termes d’influence relative du climat et de l’occupation du sol sur les dommages futurs. [less ▲]

Innovative modelling of 3D unsaturated flow in porous media by coupling independent models for vertical and lateral flows

in Journal of Computational & Applied Mathematics (2013), 246

Experimental analysis of the stability of cobles and boulders in high-gradient rivers

in Symposium on Two-phase Modelling for Sediment Dynamics in Geophysical Flows (2013)

Feedback from reservoir sedimentation on the flow pattern in rectangular basins

in 6th International Conference on Scour and Erosion (ICSE) (2012, August)

Despite simple geometries, flow in shallow rectangular reservoirs show complex recirculation patterns, which strongly influence the sediment deposits and, in practice, affect the operation and maintenance ... [more ▼]

Despite simple geometries, flow in shallow rectangular reservoirs show complex recirculation patterns, which strongly influence the sediment deposits and, in practice, affect the operation and maintenance costs of such facilities. Based on composite modelling, this research characterizes flow and sedimentation patterns in geometric conditions which have not been investigated so far. Velocity fields developing in rectangular shallow reservoirs (h = 0.2 m) with different asymmetric locations of the inlet and the outlet channels were experimentally investigated. Tests were performed in a reservoir geometry (4.5 m x 4 m) characterized by a stable symmetric flow pattern in the basic symmetric configuration, at constant hydraulic conditions; the aim was to evaluate exclusively the effect of channels displacing on the flow patterns and on the sedimentation of suspended solids. Horizontal velocity components were measured by ultrasound velocity profilers in the entire reservoir and maps of velocity vectors were obtained. Velocity measurements were performed both with clear water and with an inflowing suspended load. At the end of the experiments sediments deposits thickness on the entire reservoir bottom was measured by a laser light method, and maps of sediments deposits thickness were produced. Reservoir trapping efficiency was evaluated, but no significant influence of inlet and outlet channels location on trapping efficiency was observed. Numerical simulations were performed with the depth-averaged model WOLF 2D, in order to assess the ability of the model to reproduce the different types of flow patterns found in the experiments. In particular, a sensitivity analysis on bottom roughness as well as on the turbulence closure model and parameter was performed, in order to analyze a possible feedback effect of sediment deposits and/or suspended load on the type of flow pattern. [less ▲]

Experimental analysis of PKW hydraulic performance and geometric parameters optimum

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 ▲]

Management of the Interface between Fixed-Depths Unsaturated and Saturated Soils; Mathematical Model and 1-dimensional Interpretation

in Proceedings of the 2nd IAHR Europe Congress (2012, June)

Hydraulic modelling of Piano Key Weirs: a composite approach

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 ▲]