References of "Erpicum, Sébastien"
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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 detailHydromorphological restauration of Alpine rivers
Rulot, François ULg; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

Conference (2011, November)

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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 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 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 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 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 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 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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