References of "Erpicum, Sébastien"
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See detailFlow field in shallow reservoir with varying inlet and outlet position
Ferrara, Velia; Erpicum, Sébastien ULiege; Archambeau, Pierre ULiege et al

in Journal of Hydraulic Research (in press)

Shallow reservoirs are used for multiple purposes, such as storm water retention and trapping of sediments. Reliable predictions of the flow fields are necessary to inform the design and operation of ... [more ▼]

Shallow reservoirs are used for multiple purposes, such as storm water retention and trapping of sediments. Reliable predictions of the flow fields are necessary to inform the design and operation of these structures. Using numerical simulations, we performed a systematic analysis of the influence of the location of the inlet and outlet on the flow fields developing in rectangular shallow reservoirs of various sizes. Depending on the relative location of the inlet and outlet with respect to the reservoir centreline, contrasting flow patterns are obtained, involving either no flow reattachment, or a jet reattached on either of the reservoir sidewalls. The results reveal also the occurrence of bi-stable flow configurations, i.e. different steady state flow fields are reached depending on the flow history. This is of high relevance for the design of shallow reservoirs as such configurations should certainly be avoided to achieve a robust hydraulic sizing of the reservoir. [less ▲]

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See detailHydraulic determination of dam releases to generate warning waves in a mountain stream: performance of an analytical kinematic wave model
Stilmant, Frédéric; Pirotton, Michel ULiege; Archambeau, Pierre ULiege et al

in Journal of Hydraulic Engineering (in press)

In this case study, we study the generation of warning waves with prescribed characteristics in a mountain stream. We determine which dam release will generate the desired warning wave. We solve this ... [more ▼]

In this case study, we study the generation of warning waves with prescribed characteristics in a mountain stream. We determine which dam release will generate the desired warning wave. We solve this inverse problem following a two-model approach. An analytical kinematic model is used for a preliminary design of the dam release and a detailed two-dimensional (2D) fully dynamic model is used to converge to the final solution. Although the presented case study is far from an idealized academic case, the analytical model performs well and, beyond its role for preliminary design, turns out to be of prime interest for both understanding and discussing the results of the detailed 2D model. The complex interactions between the release hydrograph, the geometry of the river and the friction formula are brought to light by the analytical model, which highlights the complementarity of both models and the usefulness of such a two-model approach. [less ▲]

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See detailPressure and velocity on an ogee spillway crest operating at high head ratio: experimental measurements and validation
Peltier, Yann; Dewals, Benjamin ULiege; Archambeau, Pierre ULiege et al

in Journal of Hydro-Environment Research (in press)

This paper aims at validating pressure and velocity measurements conducted in two physical scale models of an ogee spillway crest operating at heads largely greater than the design head. The design head ... [more ▼]

This paper aims at validating pressure and velocity measurements conducted in two physical scale models of an ogee spillway crest operating at heads largely greater than the design head. The design head of the second model is 50% smaller than the one of the first model. No pier effect or air venting is considered in the study. The velocity field is measured by Bubbles Image Velocimetry. The relative pressure along the spillway crest is measured using pressure sensors. Comparison of measured velocities between both spillways indicates low scale effects, the scaled-profiles collapsing in most parts of the flow. By contrast, measurements of relative pressure along the spillway crest differ for large heads. A theoretical velocity profile based on potential flow theory and expressed in a curvilinear reference frame is fitted to the velocity measurements, considered as reference, for extrapolating the velocity at the spillway crest. Comparing the extrapolated velocity at the spillway crest and the velocity calculated from the relative pressure considering a potential flow finally emphasizes that bottom pressure amplitudes seem overestimated for the larger spillway, while an averaging effect might operate for the pressure measurements on the smaller spillway. [less ▲]

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See detailMaximum energy dissipation to explain velocity fields in shallow reservoirs
Westhoff, Martijn; Erpicum, Sébastien ULiege; Archambeau, Pierre ULiege et al

in Journal of Hydraulic Research (in press)

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern: Short rectangular reservoirs reveal a straight jet from inlet to outlet with on ... [more ▼]

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern: Short rectangular reservoirs reveal a straight jet from inlet to outlet with on both sides identical recirculation zones. In longer reservoirs, the main jet reattaches to the side of the reservoir leading to a small and a large recirculation zone. Previous studies found an empirical geometric relation describing the switch between these two flow patterns. In this study, we demonstrate, with a simple analytical model, that this switch coincides with a maximization of energy dissipation in the shear layer between the main jet and recirculation zones: Short reservoirs dissipate more energy when the flow pattern is symmetric, while longer reservoirs dissipate more energy with an asymmetric pattern. This approach enables to predict the flow patterns without detailed knowledge of small scale processes, potentially useful in the early phase of reservoir design. [less ▲]

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See detailInfluence of urban pattern on inundation flow in floodplains of lowland rivers
Bruwier, Martin ULiege; Mustafa, Ahmed Mohamed El Saeid ULiege; Aliaga, Daniel G. et al

in Science of the Total Environment (2018), 622–623

The objective of this paper is to investigate the respective influence of various urban pattern characteristics on inundation flow. A set of 2,000 synthetic urban patterns were generated using an urban ... [more ▼]

The objective of this paper is to investigate the respective influence of various urban pattern characteristics on inundation flow. A set of 2,000 synthetic urban patterns were generated using an urban procedural model providing locations and shapes of streets and buildings over a square domain of 1 x 1 km². Steady two-dimensional hydraulic computations were performed over the 2,000 urban patterns with identical hydraulic boundary conditions. To run such a large amount of simulations, the computational efficiency of the hydraulic model was improved by using an anisotropic porosity model. This model computes on relatively coarse computational cells, but preserves information from the detailed topographic data through porosity parameters. Relationships between urban characteristics and the computed inundation water depths have been based on multiple linear regressions. Finally, a simple mechanistic model based on two district-scale porosity parameters, combining several urban characteristics, is shown to capture satisfactorily the influence of urban characteristics on inundation water depths. The findings of this study give guidelines for more flood-resilient urban planning. [less ▲]

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See detailRésilience urbaine et risque d’inondation : apports du numérique et de l’expérimental
Dewals, Benjamin ULiege; Erpicum, Sébastien ULiege; Archambeau, Pierre ULiege et al

Scientific conference (2017, December 07)

L’urbanisation croissante et l’intensification des extrêmes hydrologiques accentuent l’importance de la gestion du risque d’inondation. Différents mesures en matière d’aménagement du territoire peuvent ... [more ▼]

L’urbanisation croissante et l’intensification des extrêmes hydrologiques accentuent l’importance de la gestion du risque d’inondation. Différents mesures en matière d’aménagement du territoire peuvent contribuer à maîtriser la vulnérabilité accrue des zones construites, mais leurs effets sont rarement quantifiés de manière objective. Nous montrerons des exemples d’analyse prospective de l’évolution du risque d’inondation pour différents scénarios d’urbanisation. Les nouvelles constructions affectent non seulement la vulnérabilité dans les plaines inondables, mais également les écoulements d’inondation. Une analyse systématique de l’impact hydrologique de choix en matière d’aménagement de la ville sera présentée. Des implications pratiques en matière de résilience des tissus urbains seront mises en évidence. Nous soulignerons également la complémentarité entre modélisation numérique et expérimentale sur cette thématique, ainsi que l’importance des incertitudes qui affectent de façon contrastée les différentes étapes de la modélisation et présentent une hétérogénéité spatiale à ne pas négliger. [less ▲]

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See detailProtection contre l’affouillement du barrage de Poses-Amfreville : études sur modèles réduit et numérique
Sixdenier, Jean Philippe; Shaiek, Salah; Erpicum, Sébastien ULiege et al

in Loudière, Daniel (Ed.) Hydraulique des barrages et des digues (2017, December)

The worrying development of a scouring downstream of the Poses dam decided Voies Navigables de France to carry on tests on experimental and numerical hydraulic models in order to design a suitable ... [more ▼]

The worrying development of a scouring downstream of the Poses dam decided Voies Navigables de France to carry on tests on experimental and numerical hydraulic models in order to design a suitable protection solution. In a first step, the study enabled to identify the operation situations for which scouring risk was the most important. Second, a rip rap protection made of 3-6 t blocks on a length of 30 m downstream of the dam has proved to be able to resist the whole realistic flow solicitations. [less ▲]

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See detailExperimental investigation of fluvial dike breaching due to flow overtopping
El Kadi Abderrezzak, Kamal; Rifai, Ismail; Erpicum, Sébastien ULiege et al

Conference (2017, December)

The failure of fluvial dikes (levees) often leads to devastating floods that cause loss of life and damages to public infrastructure. Overtopping flows have been recognized as one of the most frequent ... [more ▼]

The failure of fluvial dikes (levees) often leads to devastating floods that cause loss of life and damages to public infrastructure. Overtopping flows have been recognized as one of the most frequent cause of dike erosion and breaching. Fluvial dike breaching is different from frontal dike (embankments) breaching, because of specific geometry and boundary conditions. The current knowledge on the physical processes underpinning fluvial dike failure due to overtopping remains limited. In addition, there is a lack of a continuous monitoring of the 3D breach formation, limiting the analysis of the key mechanisms governing the breach development and the validation of conceptual or physically-based models. Laboratory tests on breach growth in homogeneous, non-cohesive sandy fluvial dikes due to flow overtopping have been performed. Two experimental setups have been constructed, permitting the investigation of various hydraulic and geometric parameters. Each experimental setup includes a main channel, separated from a floodplain by a dike. A rectangular initial notch is cut in the crest to initiate dike breaching. The breach development is monitored continuously using a specific developed laser profilometry technique. The observations have shown that the breach develops in two stages: first the breach deepens and widens with the breach centerline being gradually shifted toward the downstream side of the main channel. This behavior underlines the influence of the flow momentum component parallel to the dike crest. Second, the dike geometry upstream of the breach stops evolving and the breach widening continues only toward the downstream side of the main channel. The breach evolution has been found strongly affected by the flow conditions (i.e. inflow discharge in the main channel, downstream boundary condition) and floodplain confinement. The findings of this work shed light on key mechanisms of fluvial dike breaching, which differ substantially from those of dam breaching. These specific features need to be incorporated in flood risk analyses involving fluvial dike breach and failure. In addition, a well-documented, reliable data set, with a continuous high resolution monitoring of the 3D breach evolution under various flow conditions, has been gathered, which can be used for validating numerical models. [less ▲]

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See detailTo which extend inundations are influenced by urban patterns?
Bruwier, Martin ULiege; Archambeau, Pierre ULiege; Erpicum, Sébastien ULiege et al

Conference (2017, November 17)

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See detailAvailable tools for the quantification of the evolution of future flood risk in Wallonia
Bruwier, Martin ULiege; Archambeau, Pierre ULiege; Pirotton, Michel ULiege et al

Conference given outside the academic context (2017)

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See detailInfluence de la géométrie du quadrant amont et comportement hydraulique sous forte charge des seuils profilés standard
Erpicum, Sébastien ULiege; Pirotton, Michel ULiege; Blancher, Benoit et al

in Loudière, Daniel (Ed.) Hydraulique des barrages et des digues (2017, November)

In order to study the variation of the hydraulic characteristics of ogee-crested weirs for upstream heads higher than the design head, several profiles have been tested on an experimental facility ... [more ▼]

In order to study the variation of the hydraulic characteristics of ogee-crested weirs for upstream heads higher than the design head, several profiles have been tested on an experimental facility specifically designed and instrumented. These profiles have been defined regarding the real profiles of spillways of dams operated by EDF as well as the most used geometry of the literature. The experimental tests have been supplemented by numerical modeling, whose results were found to be very similar. The analysis shows that the discharge coefficient increases with the upstream head until head ratios around 5.5. This evolution follows very well the power equations from the literature. For higher head ratios, the discharge coefficient abruptly decreases from a value around 0.6 to a value around 0.55. This decrease corresponds to the apparition between the main flow and the weir of a low velocity area (the lower nappe does no more correspond to the weir profile). The analysis also shows a significant reduction of the discharge coefficient (around 10%) if the upstream quadrant design head is higher than 2 times the design head of the downstream quadrant. On the contrary, no modification of the discharge coefficient is measured if the upstream quadrant design head is smaller than the downstream quadrant one. [less ▲]

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See detailNos cours d'eau, une source d'énergie renouvelable passée, présente et future
Erpicum, Sébastien ULiege

Conference given outside the academic context (2017)

L’exploitation de l’énergie hydraulique, verte & renouvelable, a façonné au fil des siècles nombre de nos cours d’eau. Dans le contexte actuel de décentralisation de la production électrique ... [more ▼]

L’exploitation de l’énergie hydraulique, verte & renouvelable, a façonné au fil des siècles nombre de nos cours d’eau. Dans le contexte actuel de décentralisation de la production électrique & d’exploitation des sources non polluantes, l’hydroélectricité trouve un regain d’intérêt qui peut souvent s’accompagner de la remise en valeur d’un patrimoine bâti d’exception. La conférence détaillera ces points & les illustrera par de nombreux exemples. Parmi ceux-ci, la turbine hydroélectrique récemment mise en service au centre de Comblain-au-Pont, avec l’aide de la Région Wallonne, pour assurer l’autonomie énergétique de la Maison communale. [less ▲]

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See detailNUMERICAL STUDY OF TURBULENT OSCILLATIONS AROUND A CYLINDER: RANS CAPABILITIES AND SENSITIVITY ANALYSIS
Valero Huerta, Daniel ULiege; Bung, Daniel B.; Erpicum, Sébastien ULiege et al

in Proceedings of the 37th IAHR World Congress (2017, August)

Numerical modelling is commonly used in a large range of environmental fluid mechanics applications. It has become widely accepted and, with increasing computer power, the employed models are increasing ... [more ▼]

Numerical modelling is commonly used in a large range of environmental fluid mechanics applications. It has become widely accepted and, with increasing computer power, the employed models are increasing also in complexity. Reynolds Averaged Navier-Stokes (RANS) equations are the preferred approach for 3D problems, being especially suited for the computation of the mean flow. However, little is known about RANS performance for the fluctuating quantities; being reasonable to expect an impairment in the accuracy. In this study, a simple geometry (cylindrical pier) is subject to different numerical settings in order to assess their effect on the development of the physically based flow instabilities. Mesh refinement has shown to enhance the perturbation growth rate while maximum CFL value has not produced any effect. RNG k-ϵ and k-ω have shown to be more dissipative than k-ϵ. Some advection schemes seem to increase the spurious perturbation converging to the physically based ones. Finally, introducing an experimentally based perturbation at the inlet has proven to speed up the process. [less ▲]

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See detailPhysical modeling of overtopping induced fluvial dike failure: effects of the channel flow and floodplain innundation
Rifai, Ismail; Erpicum, Sébastien ULiege; Archambeau, Pierre ULiege et al

Conference (2017, August)

Fluvial dikes have been constructed as flood defense structures, but their failure may lead to casualties and major damages in the protected areas. Flow overtopping is listed as the main cause of dike ... [more ▼]

Fluvial dikes have been constructed as flood defense structures, but their failure may lead to casualties and major damages in the protected areas. Flow overtopping is listed as the main cause of dike failure. An accurate assessment of the breach evolution is a prerequisite to a sound flood risk assessment and management. in contrast, the current knowledge of the physical processes involved in fluvial dike failure by overtopping remains highly fragmented. This paper presents experimental tests on the breaching of homogenous sand-dikes in a fluvial configuration, i.e. the flow is parallel to the longitudinal dike axis. Overtopping is initiated over a pilot notch at the dike crest. Experiments are performed for different inflow discharges in the main channel and under different levels of floodplain confinement. The transient evolution of the dike geometry is monitored using a laser profilometry technique. The detailed reconstruction of the breach formation and expansion provides key insights into the mechanisms involved in the failure of fluvial dikes. Results show that the breach development differs highly from experiments disregarding the flow parallel to the dike axis (i.e. frontal configuration) as in the fluvial configuration the breach develops mainly in the flow direction and the floodplain water level strongly conditions the breach horizontal and vertical extent. [less ▲]

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See detailInfluence of urban patterns on flooding
Bruwier, Martin ULiege; Mustafa, Ahmed; Aliaga, Daniel et al

in E-proceedings of the 37th IAHR World Congress (2017, August)

The goal of this paper is to identify the respective influence of different characteristics of urban patterns on urban flooding. A set of 2,290 alternate urban patterns was generated randomly using an ... [more ▼]

The goal of this paper is to identify the respective influence of different characteristics of urban patterns on urban flooding. A set of 2,290 alternate urban patterns was generated randomly using an urban generator tool providing the geometry of buildings and their relative location to the ground, over a square area of 1 km². Steady 2-D hydraulic computations were performed for these 2,290 different urban patterns with identical hydraulic boundary conditions. The computational time was reduced by using an anisotropic porosity model. This model uses relatively coarse computational cells; but preserves information from the detailed topographic data through the use of porosity parameters. Based on the computed maps of waterdepths for the 2,290 urban patterns, a sensitivity analysis based on a multiple linear regression was performed to outline the most influential urban characteristics. [less ▲]

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See detailModèles de porosité pour les inondations urbaines
Dewals, Benjamin ULiege; Bruwier, Martin ULiege; El Saeid Mustafa, Ahmed Mohamed ULiege et al

Scientific conference (2017, July 25)

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See detailOn the transition between symmetric and asymmetric flow in rectangular shallow reservoirs - a case of maximum energy dissipation?
Westhoff, Martijn; Erpicum, Sébastien ULiege; Archambeau, Pierre ULiege et al

Conference (2017, June 28)

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern. Short rectangular reservoirs reveal a straight jet from inlet to outlet with ... [more ▼]

Shallow reservoirs are often used as sediment traps or storage basins, in which sedimentation depends on the flow pattern. Short rectangular reservoirs reveal a straight jet from inlet to outlet with identical recirculation zones on both sides. In longer reservoirs, the main jet reattaches to the side of the reservoir leading to small and large recirculation zones. Previous studies have found an empirical geometric relation describing the switch between these two flow patterns. In this study, we demonstrate, with a simple analytical model, that this switch coincides with a maximization of energy dissipation in the shear layer between the main jet and recirculation zones: Short reservoirs dissipate more energy when the flow pattern is symmetric, while longer reservoirs dissipate more energy with an asymmetric pattern. This approach enables the prediction of the flow patterns without detailed knowledge of small scale processes, potentially useful in the early phase of reservoir design. [less ▲]

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See detailOn the transition between symmetric ans asymmetric flow in rectangular shallow reservoirs - a case of maximum energy dissipation?
Westhoff, M.C.; Erpicum, Sébastien ULiege; Archambeau, Pierre ULiege et al

Conference (2017, June)

Shallow reservoirs are often used in hydraulic engineering as sediment traps or storage basins. For short rectangular reservoirs, the main jet flows straight from the inlet to the outlet with on both sides ... [more ▼]

Shallow reservoirs are often used in hydraulic engineering as sediment traps or storage basins. For short rectangular reservoirs, the main jet flows straight from the inlet to the outlet with on both sides symmetric recirculation zones. In longer reservoirs, however, the main jet reattaches to the side of the reservoir leading to a small and a large recirculation zone. Previous studies have found an empirical geometric relation describing the switch between these two flow pattems. In this study, we demonstrate with a simple analytical model, that this switch in flow pattem coincides with a maximization of energy dissipation in the shear layer between the main jet and the recirculation zones. We show that for short reservoir lengths, energy dissipation is higher in the case of a symmetric fiow pattern, while for longer reservoir the energy dissipation is higher for asymmetric flow pattems. The simulated switch between the two flow patterns appears to be very close to the empirical relation. The strength of this approach lies in the fact that no detailed knowledge of small scale processes is needed, which may prove useful at an early stage of reservoir design. [less ▲]

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