References of "Erpicum, Sébastien"
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See detailModélisation numérique hydrosédimentaire au service de la gestion durable des sédiments
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2012, October)

Le groupe de recherches HECE de l’ULg développe depuis plus de dix ans les systèmes de modélisation hydrosédimentaire WOLF. Intégrant des modules de simulation 1D, 2D-horizontal, 2D-vertical et 3D, il ... [more ▼]

Le groupe de recherches HECE de l’ULg développe depuis plus de dix ans les systèmes de modélisation hydrosédimentaire WOLF. Intégrant des modules de simulation 1D, 2D-horizontal, 2D-vertical et 3D, il permet la modélisation intégrée des diverses phases d’écoulement depuis le ruissellement hydrologique sur les bassins versants jusqu’aux écoulements fluviaux et au voisinage des structures hydrauliques. Deux gammes d’applications récentes du modèle 2D seront présentées : - écoulements de crues et inondations influencés par les dépôts dans les voies navigables et analyse de l’efficacité d’opérations de dragage ; - prédiction de l’engravement de réservoirs (aménagements hydroélectriques) et simulation de mesures de gestion de ces sédiments (opérations de chasse). L’accent sera mis tant sur le volet applicatif que sur les développements numériques innovants sous-jacents. [less ▲]

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See detailFeedback from reservoir sedimentation on the flow pattern in rectangular basins
Camnasio, Erica; Erpicum, Sébastien ULg; Orsi, Enrico et al

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 ▲]

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See detailExperiment investigations of 2D stationary mixed flows and numerical conparison
Nguyen, Van Nam ULg; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

in Proceedings of the 2nd IAHR Europe Congress (2012, June 27)

Experimental investigations have been carried out to observe the mechanisms of stationary mixed flows in a flume combined with a conduit. The tests have been performed for varied discharges, considering ... [more ▼]

Experimental investigations have been carried out to observe the mechanisms of stationary mixed flows in a flume combined with a conduit. The tests have been performed for varied discharges, considering two 4.2m long rectangular channels 0.985m wide and 0.50m deep, linked by a 2m long closed conduit with a 0.20m wide and 0.15m high rectangular cross-section, located at the channels bottom along the right bank. The experimental results have been compared with numerical modeling performed using an original 2D numerical model, dealing with mixed flows using a single set of equations. [less ▲]

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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 detailMultiphase flow from a civil engineering perspective
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2012, June)

For over 15 years, our research group at the University of Liege has been conducting basic and applied research on flow and transport phenomena involved in environmental and civil engineering applications ... [more ▼]

For over 15 years, our research group at the University of Liege has been conducting basic and applied research on flow and transport phenomena involved in environmental and civil engineering applications. The research topics cover a wide range of multiphase flow, including aerated flow and sediment-laden flow. The research group has developed the modelling system WOLF, which performs 1D, 2D-horizontal, 2D-vertical and 3D simulations of free surface and pressurized flow, coupled with air- or sediment-transport as well as morphodynamic simulations [9]. An original depth-averaged k- model is used to evaluate the eddy viscosity and diffusivity [5]. In a composite modelling approach [e.g., 2, 8], the numerical simulations have systematically been carried out in parallel with experimental research in flumes and scale models of hydraulic structures [3, 4, 7]. A particularly challenging issue in multiphase flow modelling is the need to handle accurately and efficiently a wide range of time scales involved in the relevant phenomena (e.g., sediment transport). Therefore, the modelling system provides a series of complementary numerical schemes designed to be combined for covering the whole range of relevant time scales. This presentation will provide examples of analysis of aerated flow, such as on stepped spillways and in penstocks [6], and of reservoir sedimentation. In particular, recent experimental findings have revealed that the flow pattern in rectangular shallow reservoirs is considerably modified at a macro-scale when suspended load is added to the flow [1]. This sudden change in flow pattern has been observed to take place quickly after the beginning of the experiment, so that it is very unlikely to result from morphodynamic changes of the reservoir bottom. Therefore, the numerical model WOLF has been used to investigate the effect of two other possible feedback mechanisms of sediment deposits and suspended load on the overall flow pattern, namely (i) increased bottom roughness and (ii) turbulence damping. From the simulations results, it can be argued that turbulence intensity is probably the main cause for the flow pattern to change at a macro-scale, as suspended load exerts a turbulence damping effect at a micro-scale in the two-phase flow (water-sediment mixture). Finally, the analysis of flow and sediment transport in shallow rectangular reservoirs also highlights the need, when structures are designed based on numerical simulations, to carefully check the stability of the computed flow fields needs by conducting sensitivity analyses, not only with respect to the modelling parameters but also with respect to the initial conditions. [less ▲]

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See detailThree‐phase Bi‐layer Model for Simulating Mixed Flows
Kerger, François ULg; Archambeau, Pierre ULg; Dewals, Benjamin ULg et al

in Journal of Hydraulic Research (2012), 50(3), 312-319

Mixed flows characterized by a simultaneous occurrence of free surface and pressurized flows are often encountered in hydraulic engineering. Numerous researches have been dedicated to unify the ... [more ▼]

Mixed flows characterized by a simultaneous occurrence of free surface and pressurized flows are often encountered in hydraulic engineering. Numerous researches have been dedicated to unify the mathematical description of both flows. Herein, shock-capturing models succeed in giving a unique set of equations. However, no method accounts for both air-entrapment and air-entrainment. This study proposes an original model to simulate air–water interactions in mixed flows. The new approach relies on the area-integration of a three-phase model over two layers. The applicability of this free surface model is extended to pressurized flows by a modified pressure term accounting for the dispersed air. The derived modelling system WOLF IMPack is then validated. The code successfully simulates open channel flows, mixed flows and water hammer in a unified framework, including air–water interactions, in structures like the drainage network. [less ▲]

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See detailExperimental and numerical investigation of a meandering jet in shallow rectangular reservoirs under different hydraulic conditions
Camnasio, Erica; Pirotton, Michel ULg; Erpicum, Sébastien ULg et al

in 3rd International Symposium on Shallow Flows (2012, June)

A central meandering jet in shallow rectangular reservoirs has been investigated numerically by the model WOLF2D, on the basis of experimental evidence of this type of flow field in two different setups ... [more ▼]

A central meandering jet in shallow rectangular reservoirs has been investigated numerically by the model WOLF2D, on the basis of experimental evidence of this type of flow field in two different setups at different scales. A sensitivity analysis has been conducted with respect to the main parameters of the model. The oscillation frequency of the transversal velocity and the characteristic Strouhal number have been calculated for different Froude numbers. A logarithmic relationship has been found between the Strouhal and the Froude numbers. [less ▲]

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See detailLong-term sediment management for sustainable hydropower
Dewals, Benjamin ULg; Rulot, François ULg; Erpicum, Sébastien ULg et al

in Sayigh, A (Ed.) Comprehensive Renewable Energy. Vol. 6 (2012)

Since the second half of the 20th century and for decades to come, sedimentation in reservoirs is challenging our ability to maintain the storage capacity needed for water supply, flood mitigation and ... [more ▼]

Since the second half of the 20th century and for decades to come, sedimentation in reservoirs is challenging our ability to maintain the storage capacity needed for water supply, flood mitigation and hydroelectricity production. This complex issue needs to be accounted for from the early stages of the design of dams and reservoirs, until the definition of operation rules oriented towards sustainable management of water and sediments. With reference to the widely-used Driver, Pressure, State, Impact, Response (DPSIR) analytical framework (European Commission 2003), the present chapter reviews key figures and trends in worldwide reservoirs sedimentation, as well as analyzes contemporary sediment management strategies. Besides setting some fundamentals of reservoir sedimentation and summarizing up-to-date background information on rate and distribution of loss of storage in the world, we identify some key driving forces of soil erosion, such as land use, urban development, agriculture and deforestation. Main mechanisms of watershed erosion and sediment yield to reservoirs are also discussed, with a focus on their spatial and temporal variation. Means for quantifying the magnitude of this pressure on reservoirs sustainability are presented, including reservoir surveys, fluvial measurements and combined approaches with numerical modelling. After a review of sedimentation impacts, both locally and downstream as well as upstream of the reservoir, we describe current experience and future opportunities of response to reservoir sedimentation. Possible measures are classified into three broad categories: sediment yield reduction, sediment routing (bypass and pass-through) and sediment removal (dredging and flushing). Pro and contras are presented for the different modes of reservoir operation, as well as their expected efficiency and some specific constraints. Predicting the sedimentation pattern as well as grain sorting processes is a prerequisite for developing optimal sediment evacuation strategies, involving for instance flushing operations. Sound modelling of sediment transport and deposition in reservoirs is highlighted as highly beneficial to support sediment management in the perspective of achieving reservoir sustainability. The chapter also illustrates how spatially distributed numerical modelling may succeed in enhancing decision-making for selecting optimal sediment management measures. [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 detailRelative impacts of climate and landuse changes on future flood damage along River Meuse in Wallonia
Beckers, Arnaud ULg; Detrembleur, Sylvain ULg; Dewals, Benjamin ULg et al

Poster (2012, April 27)

Climate change is expected to increase flood hazard across most of Europe, both in terms of peak discharge intensity and frequency. Consequently, managing flood risk will remain an issue of primary ... [more ▼]

Climate change is expected to increase flood hazard across most of Europe, both in terms of peak discharge intensity and frequency. Consequently, managing flood risk will remain an issue of primary importance for decades to come. Flood risk depends on territories’ flood hazard and vulnerability. Beside climate change, land use evolution is thus a key influencing factor on flood risk. The aim of this research is to quantify the relative influence of climate and land use changes on flood damage evolution during the 21st century. The study focuses on River Meuse in Wallonia for a 100-year flood. A scenario-based approach was used to model land use evolution. Nine urbanization scenarios for 2100 were developed: three of them assume a “current tend” land use evolution, characterized by urban sprawl, while six others assume a sustainable spatial planning, leading to an increase in density of residential areas as well as an increase in urban functions diversity. A study commissioned by the EU has estimated a 30 % increase in the 100-year discharge for River Meuse by the year 2100. Inundation modeling was conducted for the present day 100-year flood (HQ100) and for a discharge HQ100 + 30%, using the model Wolf 2D and a 5m grid resolution Digital Elevation Model (Ernst et al. 2009). Based on five different damage curves related to land use categories, the relative damage was deduced from the computed inundation maps. Finally, specific prices were associated to each land use category and allowed assessing absolute damages, which were subsequently aggregated to obtain a damage value for each of the 19 municipalities crossed by River Meuse. Results show that flood damage is estimated to increase by 540 to 630 % between 2009 and 2100, reaching 2.1 to 2.4 billion Euros in 2100. These increases mainly involve municipalities downstream of a point where the floodplain width becomes significantly larger. The city of Liège, which is protected against a 100-year flood in the present situation, would undergo about 450 million Euros damage for a 100-year flood in the 2100, i.e. in-between 21% and 25 % of the whole damage increase. The influence of climate is three to eight times higher than the effect of land use change according to the land use evolution scenarios considered. Nevertheless, these two factors have a comparable influence on seven municipalities. Consequently, although a careful spatial planning would not considerably reduce the overall flood damage at the level of theWalloon part of the Meuse Valley, more sustainable spatial planning could efficiently reduce future flood damage at the level of several most critical municipalities. Reference Ernst, J, Dewals, B, Detrembleur, S, Archambeau, P, Erpicum, S, & Pirotton, M. (2010). Micro-scale flood risk analysis based on detailed 2D hydraulic modelling and high resolution geographic data. Natural Hazards, 55(2), 181-209. [less ▲]

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See detailBenefit of using flood risk analysis at the micro level for evaluating local protection measures
Dewals, Benjamin ULg; Detrembleur, Sylvain ULg; Archambeau, Pierre ULg et al

Conference (2012, April 23)

In numerous river basins, climate projections converge towards conditions leading to a significant increase in peak discharges both in terms of intensity and frequency. Therefore, managing flood risk will ... [more ▼]

In numerous river basins, climate projections converge towards conditions leading to a significant increase in peak discharges both in terms of intensity and frequency. Therefore, managing flood risk will remain an issue of primary importance. Besides, it is currently shifting from the search for full protection against flooding towards the management of the impacts of flooding. In this respect, the elaboration of effective flood management strategies should rely on an integrated risk-based approach, encompassing not only hydraulic criteria but also economic, social and environmental factors. In addition, the considered level of detail in the analysis should be relevant given the available data and the expected outcomes. While such risk analyses have so far been mostly undertaken at a macro- or meso-scale, the herein described analysis is performed at a micro-scale, meaning that the considered assets are the individual buildings, parcels or facilities. [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 detailFlow patterns and sediment deposition in rectangular shallow reservoirs
Dufresne, Matthieu; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

in Water & Environment Journal (2012), 26(4), 504-510

This work involves the experimental investigation of flow patterns, preferential regions of deposition and trapping efficiency in rectangular shallow reservoirs. The main flow patterns that can be ... [more ▼]

This work involves the experimental investigation of flow patterns, preferential regions of deposition and trapping efficiency in rectangular shallow reservoirs. The main flow patterns that can be encountered in rectangular shallow reservoirs are described: symmetrical flows without any reattachment point (S0), asymmetrical flows with one reattachment point (A1), and asymmetrical flows with two reattachment points (A2). The influence of geometrical and hydraulic parameters on reattachment lengths is intensively investigated. A shape parameter is introduced to classify symmetrical and asymmetrical flows. For each flow pattern, the preferential regions of deposition are studied. To conclude, a number of practical recommendations are given. Reservoirs with a shape parameter lower than 6.2 limit sediment deposition. Reservoirs with a shape parameter greater than 6.8 are favourable for sediment deposition. Finally, perspectives for maximizing and minimizing deposition are given, respectively by exploiting the great trapping potential of the flow pattern A1 and the poor trapping potential of the flow pattern S0. [less ▲]

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