References of "Dewals, Benjamin"
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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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See detailFlood risk management and reservoir operation
Dewals, Benjamin ULg

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

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See detailA unified approach for sediment routing over partially non-erodible bottoms and wetting-drying areas
Rulot, François ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Proceedings of the 34th IAHR World Congress (2011)

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See detailAdvanced topics in sediment transport modelling: non-alluvial beds and hyperconcentrated flows
Dewals, Benjamin ULg; Rulot, François ULg; Erpicum, Sébastien ULg et al

in Ginsberg, Silvia Susana (Ed.) Sediment transport (2011)

In this chapter, we first present an original two-phase flow model for the water-sediment mixture, acting as a unified basis for all our subsequent developments. Next, we focus on two topics in which we ... [more ▼]

In this chapter, we first present an original two-phase flow model for the water-sediment mixture, acting as a unified basis for all our subsequent developments. Next, we focus on two topics in which we have made original contributions, namely sediment routing on alluvial and non-alluvial beds and modelling of transient hyperconcentrated flows. In both cases, we use our original two-phase flow modelling framework to derive specific governing equations, for which we discuss their mathematical properties, detail appropriate finite volume numerical scheme and demonstrate their validity through a number of test cases. [less ▲]

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See detail2D-Vertical Model for Free Surface Incompressible Flows: Validation and Applications
Detrembleur, Sylvain; Dewals, Benjamin ULg; Pirotton, Michel ULg

in Proc. 34th IAHR World Congress - Balance and Uncertainty (2011)

Efficient design of hydraulic structures such as weirs and bottom outlets requires a detailed description of the complex turbulent flows occurring on these structures. Compared to laboratory experiments ... [more ▼]

Efficient design of hydraulic structures such as weirs and bottom outlets requires a detailed description of the complex turbulent flows occurring on these structures. Compared to laboratory experiments, numerical modeling offers more flexibility and cost-effectiveness to test different designs. The non-hydrostatic 2D-vertical model presented here solves the RANS equations for incompressible flows in the vertical plane. It is based on the projection method for pressure-velocity coupling, while free surface tracking is conducted by means of the level set technique and Sussman’s velocity extension algorithm. It enables to predict accurately the flow pattern in the vertical plane and deals with multiple interfaces (jets, drops…). The solver has been validated for both steady and unsteady free surface flows, based on theoretical and experimental data. The paper will detail the application of the model to a pressurized flow and to a sloshing tank. [less ▲]

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See detailDepth-averaged flowslides model: validation and application to tailings dams and waste dumps failures
Dewals, Benjamin ULg; Archambeau, Pierre ULg; Detrembleur, Sylvain ULg et al

in Chanson, Hubert (Ed.) Proc. of the 34th IAHR World Congress: Balance and Uncertainty: Water in a Changing World (2011)

Flowslides induced by the failure of tailing dams or waste dumps constitute significant industrial hazards. Examples in the past have demonstrated their high potential for casualties and damage ... [more ▼]

Flowslides induced by the failure of tailing dams or waste dumps constitute significant industrial hazards. Examples in the past have demonstrated their high potential for casualties and damage. Geotechnical analyses provide nothing more than the failure criteria. In contrast, once the structure fails, the fluidized material propagates rapidly as a non-Newtonian flow, requiring thus a hydraulic analysis. This paper presents an advanced 2D depth-averaged flow model which accommodates the particular rheology of flowslides, including visco-plasticity and frictional behavior accounting for pore pressure. Based on mass and momentum conservation for the mixture of soil and interstitial fluid, the finite volume model handles flow propagation on dry areas and includes an original treatment of the yield stress in 2D. At a crossroads of geotechnical and hydraulic engineering, the paper depicts the elaboration and validation of a new model readily available for hazard mapping, including extent of affected areas, maximum depths and arrival time. [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 detailAn exact Riemann Solver and Godunov Scheme for Simulating Highly Transient Mixed Flows
Kerger, François ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Journal of Computational & Applied Mathematics (2011), 235

Detailed reference viewed: 114 (24 ULg)