References of "Dewals, Benjamin"
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See detailSemi-explicit modelling of watersheds with urban drainage systems
Dewals, Benjamin ULg; Archambeau, Pierre ULg; Khuat Duy, Bruno et al

in Engineering Applications of Computational Fluid Mechanics (2012), 6(1), 46-57

A trade-off methodology has been developed to account for impervious surfaces and drainage effects accurately, without the need for modelling the entire drainage network in detail. Undrained impervious ... [more ▼]

A trade-off methodology has been developed to account for impervious surfaces and drainage effects accurately, without the need for modelling the entire drainage network in detail. Undrained impervious areas have been distinguished from drained ones. Rain falling on the former has been discharged as overland flow, whereas flow on the later has been routed separately using “virtual pipes”, which enable a simplified process-oriented modelling of the drainage network. [less ▲]

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See detailQuantifying flood damages for climate-change adaptation on a transnational river basin
Fournier, Maïté; Sinaba, Benjamin; Dewals, Benjamin ULg et al

in Schüttrumpf (Ed.) Floods: a permanent challenge! (2012)

The Meuse river basin is shared by five countries. Climate change in the future decades could either lead to a dryer or a wetter situation. In order to build an adaptation strategy that would cope with ... [more ▼]

The Meuse river basin is shared by five countries. Climate change in the future decades could either lead to a dryer or a wetter situation. In order to build an adaptation strategy that would cope with both scenarios and that is agreed at the international level, water experts have set-up the AMICE project. Quantifying the flood damages is an important part of this project. It required much negotiation at every intermediary step, from the definition of climate scenarios, to the hydraulic modeling and the agreement on damage functions. [less ▲]

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See detailOn the advantage of using risk curves to assess flood protection measures
Dewals, Benjamin ULg; Detrembleur, Sylvain ULg; Archambeau, Pierre ULg et al

in Mambretti, Stefano (Ed.) Environmental Risk (2012)

Modern flood management approaches require the quantification of flood risk, accounting for the hazard component (flood frequency and inundation intensity) as well as the vulnerability of the floodplains ... [more ▼]

Modern flood management approaches require the quantification of flood risk, accounting for the hazard component (flood frequency and inundation intensity) as well as the vulnerability of the floodplains (exposure, value and susceptibility). In this chapter, we present a detailed flood risk model, in which flow computation, monetary valuation of the assets and damage calculation are conducted at the scale of individual buildings or facilities. To avoid the shortcoming of focusing on economic damage, psycho-social impacts of floods are also included in the analysis. The model has been applied to evaluate three flood protection measures on a river reach in the Meuse basin (Belgium). The resulting risk curves show that such a micro-scale risk analysis provides important insights into the relative influence of the different flood protection measures. This could neither be evaluated through a more standard hydraulic analysis nor through the quantification of flood risk by only a single number. [less ▲]

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See detailConsidering non-alluvial layers in morphodynamic modelling
Rulot, François ULg; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

Conference (2011, November)

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See detailHydromorphological restoration of Alpine rivers
Rulot, François ULg; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

Conference (2011, November)

More and more efforts are undertaken to restore rivers in a state close to their natural conditions in order to meet the Water Framework Directive requirement. This directive commits EU member states to ... [more ▼]

More and more efforts are undertaken to restore rivers in a state close to their natural conditions in order to meet the Water Framework Directive requirement. This directive commits EU member states to achieve a good ecological status of all their water bodies. It became thus very important to develop river restoration such as fish passages, bank renaturation, natural bars or meanders. Another important component of river restoration schemes is the decommissioning of man-made structures. These interventions can have significant impact on the river hydrology, hydraulics and morphology, such as bed degradation or aggradation, bank failures. Predicting these impacts of restoration schemes on the river, especially for large scale projects, should rely on detailed numerical studies. To achieve this goal, we develop a methodology to analyse different scenarios of river restoration based on several criteria related to flow, sediment transport and environment. This method is applied to the case of a French alpine river in which five hydropower plants will be replaced by a unique underground hydropower plant on the same section of river. [less ▲]

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See detailDam break flow modelling with uncertainty analysis
Dewals, Benjamin ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

Conference (2011, November)

The failure of a large dam may result in catastrophic floods in the downstream valley. However, past experience has revealed that loss of life and damage can be drastically reduced if crisis management is ... [more ▼]

The failure of a large dam may result in catastrophic floods in the downstream valley. However, past experience has revealed that loss of life and damage can be drastically reduced if crisis management is planned in advanced, including early-warning systems, organized communication and structural measures. This requires a fairly good knowledge of the inundation characteristics likely to be induced in case of a failure. Predictions of flood waves induced by dam failure are affected by a considerable level of uncertainty. Due to the extreme nature of such events, numerical models can hardly be calibrated and validated. Flow resistance parameterizations are designed for ranges of flow properties which significantly differ from those occurring during dam break flows. Large amounts of debris may also be transported by the flow and the details of the failure scenario remain usually unknown, such as sequence of dislodgement of dam wall fragments or breach formation time (e.g., Dewals et al. 2011). Nonetheless, most dam break flow studies so far have been conducted without systematic uncertainty nor sensitivity analyses. This is partly due to the high computational cost of the multidimensional flow models used to simulate dam break flows on natural topography. We present here the simulation of a real dam break flow with a systematic analysis of the uncertainty resulting from the roughness coefficient, the failure hydrograph and topographic data. The flow simulations have been conducted with the model WOLF 2D developed at the University of Liege. It solves the fully dynamic shallow-water equations based on a finite volume scheme and a self-developed flux-vector splitting (Erpicum et al. 2010a; Erpicum et al. 2010b). Monte-Carlo simulations have been used to perform the uncertainty analysis. The two-dimensional flow model is computationally too costly to perform a high number of repeated runs, as needed for Monte Carlo simulations. Therefore, a “reduced complexity model” has been set up, in the form of multidimensional Hermite polynomials. The method developed by Isukapalli et al. (Isukapalli et al. 2004) indicates the number of simulations of the complete model needed to calibrate the polynomials, as well as the parameter values to be used in these calibration runs. The methodology has been tested for a real dam break which occurred in Spain in 1982 (Alcrudo and Mulet 2007) and for which a number of observations are available (mainly maximum water depths at different locations in a town). The presentation will show the applicability and efficiency of the methodology, which is readily available for real-world analyses. Such uncertainty analysis for dam break flows disclose crucial information for practical risk management. In particular, they reveal that the uncertainty ranges on maximum water depth and time of arrival of the front are not symmetric (overestimation vs. underestimation) and very unevenly distributed in space. [less ▲]

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See detailDike-break induced flows: a simplified model
Stilmant, Frédéric ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

Conference (2011, November)

A simplified model for the prediction of the steady-state outflow through a breach in an inland dike is presented. It consists in the application of the mass and momentum conservation principles to a ... [more ▼]

A simplified model for the prediction of the steady-state outflow through a breach in an inland dike is presented. It consists in the application of the mass and momentum conservation principles to a macroscopic control volume. A proper definition of the shape of the control volume enables to take into account the main characteristics of the flow and thus to compensate for the extreme simplification of the space discretisation of the model. At the breach, a relation derived from the shallow-water equations is used to determine the directions of the flow. Developments have been guided by numerical simulations and results have been compared to experimental data. Both the precision and the application domain of the simplified model are found satisfactory. [less ▲]

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See detailModelling of the Unsaturated Flow in Porous Media; Handling of the 3D Behaviour with uncoupled 1DV/2DH Richards Equations
Paulus, Raphaël ULg; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

in Proceedings of the 5th International Confrence on Advanced Computational Methods in Engineering (2011, November)

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See detailFlow and sedimentation in shallow reservoirs
Dewals, Benjamin ULg

Scientific conference (2011, October 03)

Les recherches présentées ici portent sur la prédiction de la sédimentation dans des bassins rectangulaires peu profonds. Ceux-ci sont fréquemment utilisés en hydraulique urbaine et constituent une ... [more ▼]

Les recherches présentées ici portent sur la prédiction de la sédimentation dans des bassins rectangulaires peu profonds. Ceux-ci sont fréquemment utilisés en hydraulique urbaine et constituent une idéalisation pertinente de multiples configurations plus complexes. Des campagnes expérimentales complémentaires ont été menées de concert à l’Université de Liège ainsi que dans d’autres laboratoires européens. Ces modélisations physiques, réalisées sur fond fixe et mobile, ont été complétées par des simulations numériques tant hydrodynamiques qu’hydrosédimentaires. Les analyses ont d’emblée révélé la complexité des écoulements dans de tels bassins, qui présentent des recirculations asymétriques malgré la symétrie hydraulique et géométrique du dispositif. La typologie des écoulements est caractérisée par plusieurs transitions, de type « bifurcations », entre écoulement symétrique et écoulement dévié. Ce faisant, nous avons abouti à une unification des critères de prédiction du type d’écoulement pour des nombres de Reynolds élevés, la formulation proposée s’appliquant à l’ensemble des résultats expérimentaux connus dans la littérature. L’étude des dépôts et du taux de rétention des sédiments dans les bassins a démontré la corrélation forte entre ces paramètres et la configuration de l’écoulement, ce qui confirme a posteriori l’importance de critères prédictifs du type d’écoulement. Ces recherches ont finalement permis d’identifier des recommandations pratiques, destinées soit à éviter les instabilités d’écoulement lors du design de bassins ou, a contrario, à exploiter pleinement ces instabilités afin de maximiser l’efficacité du bassin (stockage ou décantation). [less ▲]

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See detailFlood risk analysis in the Meuse river basin
Gouverneur, Ludovic ULg; Dewals, Benjamin ULg; Detrembleur, Sylvain ULg et al

in Urban Flood Risk Management (2011, September 21)

The goal of the study presented in the paper consists in understanding the vulnerability of economic systems to a modification of the hydrology due to climate change in the Meuse river basin. The latter ... [more ▼]

The goal of the study presented in the paper consists in understanding the vulnerability of economic systems to a modification of the hydrology due to climate change in the Meuse river basin. The latter extends over several regions in four different countries. A transnational approach is thus necessary to keep consistency throughout the international catchment. In this paper, we begin by illustrating how a strong collaboration between scientists and water authorities of the different parts of the basin has lead to a consistent approach for conducting flood risk analysis. Hazard modeling was conducted to get flood maps in the whole basin, considering various climate scenarios. In Wallonia, accurate hydraulic simulations were performed with the fully dynamic flow model WOLF2D entirely developed at the University of Liege (Erpicum et al., 2010). The outcomes of this inundation modeling constitute suitable inputs for the subsequent exposure analysis. The latter has been performed at a meso-scale using land use maps (CORINE) and geographic database (PLI), aggregated into a set of five damage categories. Recently developed damage functions, which are the key part of the vulnerability analysis, has been chosen in relation with the damage categories indentified in the exposure analysis. To determine the value of the assets, a monetary approach has been employed, with the purpose of assessing prices per square meter for each damage category. In this paper, the focus is set on comparing several approaches to calculate the specific price of the residential damage category in Wallonia, and to compare with an existing micro-scale approach (Ernst et al., 2010). [less ▲]

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See detail1D unified mathematical model for environmental flow applied to steady aerated mixed flows
Kerger, François; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

in Advances in Engineering Software (2011), 42(9), 660-670

Hydraulic models available in literature are unsuccessful in simulating accurately and efficiently environmental flows characterized by the presence of both air–water interactions and free-surface ... [more ▼]

Hydraulic models available in literature are unsuccessful in simulating accurately and efficiently environmental flows characterized by the presence of both air–water interactions and free-surface/pressurized transitions (aka mixed flows). The purpose of this paper is thus to fill this knowledge gap by developing a unified one-dimensional mathematical model describing free-surface, pressurized and mixed flows with air–water interactions. This work is part of a general research project which aims at establishing a unified mathematical model suitable to describe the vast majority of flows likely to appear in civil and environmental engineering (pure water flows, sediment transport, pollutant transport, aerated flows. . .). In order to tackle this problem, our original methodology consists in both time- and spaceaveraging the Local Instant Formulation, which includes field equations for each phase taken separately and jump conditions, over a flow cross-section involving a free-surface. Subsequently, applicability of the model is extended to pressurized flows as well. The first key result is an original 1D homogeneous Equilibrium Model which describes two-phase free-surface flows. It is proven to be fundamentally multiphase, to take into account scale heterogeneities of environmental flow and to be very easy to solve. Next, applicability of this free-surface model is extended to pressurized flows by using the classical Preissmann slot concept. A second key result here is the introduction of an original negative Preissmann slot to simulate sub-atmospheric pressurized flows. The model is then closed by using constitutive equations suitable for air–water flows. Finally, this mathematical model is discretised by means of a finite volume scheme and validated by comparison with experimental results from a physical model in the case of a steady flow in a large scale gallery. [less ▲]

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See detailTransnational harmonisation of hydraulic models
Dewals, Benjamin ULg

Scientific conference (2011, June 20)

The AMICE project covers the whole river basin of river Meuse, which extends over parts of France, Belgium, The Netherlands, Germany as well as a small portion of Luxembourg. The goal of the project ... [more ▼]

The AMICE project covers the whole river basin of river Meuse, which extends over parts of France, Belgium, The Netherlands, Germany as well as a small portion of Luxembourg. The goal of the project consists in the development of a basin-wide coordinated strategy to cope with hydrological impacts of climate change, including floods and low flows. As this strategy is intended to be truly integrated at the scale of the international basin of river Meuse, the modelling tools used (e.g., hydraulic modelling, impact assessment, risk management) are also required to be consistent throughout the basin. However, so far, there are as many models and data sets as regions. Each region has developed its own climate scenarios, rainfall-runoff models and hydrological time series as well as its own procedures for hydraulic modelling and risk modelling. This calls definitely for a transnational harmonization effort, as presented here. [less ▲]

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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 detailA Fast Universal Solver for 1D Continuous and Discontinuous Steady Flows in Rivers and Pipes
Kerger, François ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in International Journal for Numerical Methods in Fluids (2011), 66(1), 3343

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See detailNumerical investigation of flow patterns in rectangular shallow reservoirs
Dufresne, Matthieu; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

in Engineering Applications of Computational Fluid Mechanics (2011), 5(2), 247-258

The present work gives findings profitable for the person who wants to evaluate an asymmetric detach-reattach flow. In this study, the capability of a two-dimensional shallow-water numerical model to ... [more ▼]

The present work gives findings profitable for the person who wants to evaluate an asymmetric detach-reattach flow. In this study, the capability of a two-dimensional shallow-water numerical model to simulate the symmetric and asymmetric flows that can take place in rectangular shallow reservoirs varying the lateral expansion ratio and the dimensionless length is investigated. For a large lateral expansion ratio, the use of two protocols of simulation highlighted a high sensitivity of the simulated flow pattern to the initial condition. Comparison between simulated results and experimental data showed a good agreement for the critical shape parameter (combination of the lateral expansion ratio and the dimensionless length) between symmetric and asymmetric flows. A good agreement was also found for the value of the shorter reattachment length of asymmetric flows. For small lateral expansion ratios, the agreement was not so good. The model was used for even larger lateral expansion ratios in order to numerically extend the experimental dataset. This predictive work showed that the shape parameter, whose expression was only based on experiments carried out for small lateral expansion ratios, was also relevant for larger values. Moreover, the predicted values of the shorter reattachment length were also consistent with a regression only based on experimental results. [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 detailIntegrated Two-phase Drift-flux Models for Modeling Sediment Transport
Kerger, François ULg; Dewals, Benjamin ULg

in Proceedings of the Symposium on Two-phase Modelling for Sediment Dynamics in Geophysical Flows (2011, April)

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See detailFlood risk analysis and design of flood mitigation measures
Dewals, Benjamin ULg

in Contribution to the news of Belgian television RTBF (2011)

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