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Etudes théorique et sur modèles numériques et physiques du déversoir à dépression - 3ième rapport intermédiaire - Thème 1: Etudes du coefficient de débit et des pressions sur le coursier des Creager pour des charges amont largement supérieures à la charge de dimensionnement Peltier, Yann ; Erpicum, Sébastien ; Pirotton, Michel et al Report (2014) Detailed reference viewed: 21 (2 ULg)Geometric parameters influence on Piano Key Weir hydraulic performances Erpicum, Sébastien ; Archambeau, Pierre ; Pirotton, Michel et al in Chanson, Hubert; Toombes, Luke (Eds.) Hydraulic Structures and Society – Engineering Challenges (2014, June) The Piano Key Weir is a recent evolution of the traditional labyrinth weir. Thanks to a reduced foot print, this nonlinear weir can be placed on the top of gravity dams. The Piano Key Weir geometry ... [more ▼] The Piano Key Weir is a recent evolution of the traditional labyrinth weir. Thanks to a reduced foot print, this nonlinear weir can be placed on the top of gravity dams. The Piano Key Weir geometry involves a large number of geometric parameters. Several experimental studies have been carried out to investigate the main geometric parameters influencing the weir hydraulic efficiency and to define their optimal value. In this paper, the experimental data gathered at the University of Liege are re-examined to show how the weir height, the keys widths and the overhangs positions influence, for a given crest length magnification ratio, the weir discharge capacity. The theoretical rating curve of a standard linear weir is considered for comparison. The analysis highlights that the keys widths and overhangs lengths ratios influence significantly the Piano Key Weir efficiency, but less than the weir height. Considering the above mentioned results, a cost efficient design proposed in the literature is also proved to be close to the hydraulic optimum. [less ▲] Detailed reference viewed: 40 (2 ULg)Meandering flows in rectangular shallow reservoirs Peltier, Yann ; Erpicum, Sébastien ; Dewals, Benjamin Report (2014) During this research, previously unexplored meandering flows in free-surface rectangular shallow reservoirs were investigated theoretically, experimentally and numerically. For the first time, a complete ... [more ▼] During this research, previously unexplored meandering flows in free-surface rectangular shallow reservoirs were investigated theoretically, experimentally and numerically. For the first time, a complete description of the hydrodynamics of the meandering flows was obtained from laboratory experiments. An innovative procedure for the characterisation of the physics of the flow was developed based on several techniques, including Large Scale Particle Image Velocimetry (LSPIV), Proper Orthogonal Decomposition (POD) and a new topology algorithm. This research provides new insights into these fascinating meandering flows, of high practical relevance in civil and environmental engineering. Six papers were written and, so far, five of them have been accepted for publication (two in international journals and three in peer-reviewed international conference proceedings). [less ▲] Detailed reference viewed: 31 (13 ULg)Meandering jets in shallow rectangular reservoirs: POD analysis and identification of coherent structures Peltier, Yann ; Erpicum, Sébastien ; Archambeau, Pierre et al in Experiments in Fluids (2014), 55 The effect of the shallowness on meandering jets in a shallow rectangular reservoir is investigated. Four meandering flows were investigated in an experimental shallow rectangular reservoir. Their ... [more ▼] The effect of the shallowness on meandering jets in a shallow rectangular reservoir is investigated. Four meandering flows were investigated in an experimental shallow rectangular reservoir. Their boundary conditions were chosen to cover a large range of friction numbers (defined with the sudden expansion width). Due to the unsteady characteristics of the flows, a Proper Orthogonal Decomposition of the fluctu-ating part of the surface velocity fields measured using LSPIV was used for discriminating the flow struc-tures responsible for the meandering of the jet. Less than 1 % of the calculated POD modes significantly contribute to the meandering of the jet and two types of instability are in competition in such a flow con-figuration. The sinuous mode is the dominant mode in the flow and it induces the meandering of the flow, while the varicose mode is a source of local mixing and weakly participates to the flow. The fluctuating velocity fields were then reconstructed using the POD modes corresponding to 80% of the total mean fluctuating kinetic energy and the coherent structures were identified using the residual vorticity, their centres being localised using a topology algorithm. The trajectories of the structures centres emphasize that at high friction number the coherent structures are small and laterally paired in the near, middle and far fields of the jet, while with decreasing friction number the structures merge into large horizontal vortices in the far-field of the jet, their trajectories showing more variability in space and time. The analysis of the stability regime finally reveals that the sinuous mode is convectively unstable and may become absolutely unstable at the end of the reservoir when the friction number is small. [less ▲] Detailed reference viewed: 80 (30 ULg)Landuse change and future flood risk: the influence of micro-scale spatial patterns (FloodLand) - 1st progress report Dewals, Benjamin ; Bruwier, Martin ; El Saeid Mustafa, Ahmed Mohamed et al Report (2014) The goal of the project FloodLand is to investigate the complex interactions between landuse change and future flood risk. Landuse change is assumed to be mainly driven by population growth and socio ... [more ▼] The goal of the project FloodLand is to investigate the complex interactions between landuse change and future flood risk. Landuse change is assumed to be mainly driven by population growth and socio-economic factors. It affects future flood risk by altering catchment hydrology as well as vulnerability in the floodplains; but the feedback effect of (the perception of) changes in flood hazard on landuse evolution is also considered. The research is based on a chain of modelling tools, which represent parts of the natural and human systems, including: landuse change modelling, transportation modelling as an onset for the estimation of indirect flood damage, continuous hydrological modelling (forced by precipitation and temperature data disturbed according to climate change scenarios), as well as efficient hydraulic modelling of inundation flow in the floodplains. Besides reproducing a broad spectrum of processes, the modelling approach spans over multiple scales, from the regional or catchment level down to the floodplain and building levels. This distinctive feature is reflected both within the individual models and through their combination involving fine-scale detailed analyses (or data) embedded within coarser models at a broader level. [less ▲] Detailed reference viewed: 38 (20 ULg)Modèle réduit hydraulique de l’ouvrage de rejet de la station d’épuration de la vallée du Hain Erpicum, Sébastien ; Thiebaux, Benjamin ; Archambeau, Pierre et al Report (2014) Detailed reference viewed: 28 (3 ULg)Contributions to transnational flood risk management in the Meuse basin Dewals, Benjamin ; Erpicum, Sébastien ; Archambeau, Pierre et al in European Symposium on Flood Frequency Estimation and Implications for Risk Management (2014, March) Experience in transboundary river basins emphasizes the need for more cooperative transnational water management. In this respect, the Interreg IVB project AMICE aims at developing a shared adaptation ... [more ▼] Experience in transboundary river basins emphasizes the need for more cooperative transnational water management. In this respect, the Interreg IVB project AMICE aims at developing a shared adaptation strategy of the basin of the river Meuse to the hydrological impacts of climate change. The basin covers parts of France, Belgium, Germany and the Netherlands. The project combines scientific research with innovative natural and structural water retention measures, as well as enhanced transnational crisis management. In this framework, common climate and hydrological scenarios were derived for the time horizons 2021-2050 and 2071-2100. A “coordinated” procedure was set up to conduct the first hydraulic modelling of the entire river Meuse, from its spring to its mouth. For the considered climate scenarios, the increases in future flood levels were found about twice higher in the central part of the Meuse basin compared to the upper and lower parts. This distinctive spatial pattern results from the morphology of the valley. The characteristics of the hydraulic models used for this “coordinated” analysis differed significantly from one region to the other (e.g., 1D vs. 2D, steady vs. unsteady). Therefore, a more refined analysis was undertaken on a 100 km long stretch of the Meuse, crossing the border between Belgium and the Netherlands, using very similar (“harmonized”) models for the whole computation (2D unsteady models). As a result, the influence of using different interconnected models could be appreciated. The results of hydraulic modelling were used to conduct damage assessment based on a common methodology throughout the Meuse basin and combined with landuse change scenarios in the floodplains (change in vulnerability of the floodplains). In turn, several adaptation measures were tested, including upstream water retention, dredging as well as upgrade of flood defences and mobile weirs. Hydrological and hydraulic modelling was also performed for a sub-basin of the river Meuse, partly controlled by two large reservoirs. A detailed model of the operation rules of these reservoirs was implemented. This enabled to investigate the impact of the considered climate change scenarios on the performance of these multi-purpose reservoirs as well as to investigate possible enhancements in the operation rules, which may serve as adaptation measures to compensate for the detrimental effects of climate change. [less ▲] Detailed reference viewed: 36 (3 ULg)Experimental investigation of meandering jets in shallow reservoirs Peltier, Yann ; Erpicum, Sébastien ; Archambeau, Pierre et al in Environmental Fluid Mechanics (2014) Meandering flows in rectangular shallow reservoirs were experimentally investi- gated. The characteristic frequency, the longitudinal wave length and the mean lateral exten- sion of the meandering jet ... [more ▼] Meandering flows in rectangular shallow reservoirs were experimentally investi- gated. The characteristic frequency, the longitudinal wave length and the mean lateral exten- sion of the meandering jet were extracted from the first paired modes, obtained by a proper orthogonal decomposition of the surface velocity field measured by large scale PIV. The depth-normalised characteristic lengths and the Strouhal number were then compared to the main dimensionless numbers characterizing the experiments: Froude number, friction num- ber and reservoir shape factor. The normalised wave length and mean lateral extension of the meandering jet are neither correlated with the Froude number nor with the reservoir shape factor; but a clear relationship is found with the friction number. Similarly, the Strouhal num- ber is found proportional to a negative power of the friction number. In contrast, the Froude number and the reservoir shape factor enable to predict the occurrence of a meandering flow pattern: meandering jets occur for Froude number greater than 0.21 and for a shape factor smaller than 6.2. [less ▲] Detailed reference viewed: 60 (23 ULg)Réalisation et test d’un modèle réduit d’hydrolienne Erpicum, Sébastien ; Pirotton, Michel ; Dewals, Benjamin et al Report (2014) Detailed reference viewed: 32 (13 ULg)Etudes théorique et sur modèles numériques et physiques du déversoir à dépression - 2nd rapport intermédiaire - Description de la plateforme d'essau et validation de l'instrumentation Peltier, Yann ; ; Erpicum, Sébastien et al Report (2014) Detailed reference viewed: 17 (1 ULg)Barrage des Essarts (Grande Rhue) – Pré-dimensionnement de solutions du type « déversoir en labyrinthe » Erpicum, Sébastien ; Pirotton, Michel ; Dewals, Benjamin et al Report (2014) Detailed reference viewed: 66 (0 ULg)Mathematical formulations of shallow water models with porosity for urban flood modeling Bruwier, Martin ; Erpicum, Sébastien ; Archambeau, Pierre et al in ICHE 2014 : 11th International Conference on Hydroscience & Engineering (2014) Due to climate change and other environmental changes such as growing urbanization, floods are expected to become more frequent and severe in the future. However, the magnitude of these changes remains ... [more ▼] Due to climate change and other environmental changes such as growing urbanization, floods are expected to become more frequent and severe in the future. However, the magnitude of these changes remains highly uncertain. This calls generally for the analysis of a high number of scenarios and, therefore, many runs of the numerical models are necessary. Simultaneously, high-resolution topographic data have become widely available. Consequently, the present need is mainly for high performance computational models which take full benefit of the available detailed data, combining thus accuracy and high efficiency. One way to meet this challenge is the development of subgrid models. Within each computational cell of a subgrid model, the topography is represented by porosity parameters. The existing approaches for the derivation of the shallow water equations (SWE) with porosity differ in the mathematical formulations obtained, in the assumptions, in the applicability range of the models as well as in the definitions of the porosities (depthdependent/depth-independent, isotropic/anisotropic). In this paper, we review and compare the different formulations, highlight their respective limitations and criticaly analyse the major assumptions. [less ▲] Detailed reference viewed: 49 (15 ULg)Dealing with sediment transport over partly non-erodible bottoms ; Dewals, Benjamin ; Archambeau, Pierre et al in Tullis, Blake; JJanssen, Robert (Eds.) Conference proceedings of 4th IJREWHS (2014) In depth-averaged flow and morphodynamic models using a finite volume discretization based on explicit time integration, a specific difficulty can arise during a computation: the computed sediment level ... [more ▼] In depth-averaged flow and morphodynamic models using a finite volume discretization based on explicit time integration, a specific difficulty can arise during a computation: the computed sediment level can become lower than the level of a non-erodible bottom. The original developments presented in this paper enable correction of the non-physical sediment levels. The method, based on iterative limitation of the outward fluxes, is perfectly mass conservative and remains computationally efficient. The resulting model has been validated with several 1D benchmarks leading to configurations with sediment transport over a nonerodible bottom. Two interesting experimental benchmarks are highlighted in this paper to show the efficiency of numerical simulations. In these benchmarks, the computation time has been verified not to increase by more than 15% when using the new method. [less ▲] Detailed reference viewed: 11 (0 ULg)Escouloubre Piano Key weir: prototype versus scale models Erpicum, Sébastien ; Silvestri, Aurélien ; Dewals, Benjamin et al in Erpicum, Sébastien; Laugier, Frédéric; Pfister, Michael (Eds.) et al Labyrinth and Piano Key Weirs II - PKW 2013 (2014) A 1.77 m high piano key weir in operation on the Escouloubre balance basin enabled the observation of real size flows for discharges ranging from 1.2 to 10 m³/s, corresponding to upstream heads ranging ... [more ▼] A 1.77 m high piano key weir in operation on the Escouloubre balance basin enabled the observation of real size flows for discharges ranging from 1.2 to 10 m³/s, corresponding to upstream heads ranging from 11 to 48 cm. These observations are depicted and compared to the results gained on three physical models of the weir, built and operated considering a Froude similitude and geometric scale factors of, respectively, 1:7, 1:15 and 1:25. The study highlights the scale effects which may affect piano key weirs scale model studies and provides criteria to limit them. In particular, the results analysis shows that the scale models succeed in representing the flow conditions on the weir when the model upstream head is higher than 60 mm, and succeed in predicting the weir discharge capacity when the model upstream head is higher than 30 mm. [less ▲] Detailed reference viewed: 78 (1 ULg)Comparative analysis of the energy dissipation on a stepped spillway downstream of a Piano Key Weir Silvestri, Aurélien ; Archambeau, Pierre ; Pirotton, Michel et al in Erpicum, Sébastien; Laugier, Frédéric; Pfister, Michael (Eds.) et al Labyrinth and Piano Key Weirs II - PKW 2013 (2014) A systematic experimental study has been carried out to compare the residual energy at the toe of a stepped spillway of varied length considering a classical ogee-crested weir (OCW) or two different piano ... [more ▼] A systematic experimental study has been carried out to compare the residual energy at the toe of a stepped spillway of varied length considering a classical ogee-crested weir (OCW) or two different piano key weirs (PKW) at the top of the structure. Four spillway lengths have been considered on a wide range of discharge. An indirect method has been used to compute the residual flow energy at the spillway toe from water depth measurements in a horizontal channel downstream. The results indicate that uniform flow conditions, i.e. flow energy at the spillway toe independent of the spillway length, are reached on significantly shorter spillways downstream of a PKW than downstream of an OCW. However, the uniform flow energy at constant discharge on the spillway is found to vary depending on the weir type. In particular, it is smaller downstream of the OCW than downstream of the PKWs. [less ▲] Detailed reference viewed: 86 (9 ULg)An analytical approach for Piano Key weir hydraulic design ; Dewals, Benjamin ; Archambeau, Pierre et al in Erpicum, Sébastien; Laugier, Frédéric; Pfister, Michael (Eds.) et al Labyrinth and Piano Key weirs II - PKW 2013 (2014) A hydraulic design equation for Piano Key Weirs is set up using the results of a large experimental parametric study. Comparison of the analytical formulation with experi-mental data from various physical ... [more ▼] A hydraulic design equation for Piano Key Weirs is set up using the results of a large experimental parametric study. Comparison of the analytical formulation with experi-mental data from various physical modeling studies, considering idealized as well as real projects Piano Key Weirs configurations, shows a 15% accuracy in unit discharge prediction on a large range of geometric parameters values. Comparison of the proposed formulation to two other recently proposed equations highlights the importance to consider such analytical approaches inside the range of parameter values for which they have been validated. [less ▲] Detailed reference viewed: 56 (2 ULg)Climate-proofing of large reservoirs in Belgium by the development of enhanced operation rules Bruwier, Martin ; Dewals, Benjamin ; Erpicum, Sébastien et al in 3rd IAHR Europe Congress (2014) Available climate change scenarios project drier summers and more humid winters for Belgium. This study addresses the impacts of those changes on the management of two multi-purpose reservoirs located in ... [more ▼] Available climate change scenarios project drier summers and more humid winters for Belgium. This study addresses the impacts of those changes on the management of two multi-purpose reservoirs located in the Vesdre basin, and the search of enhanced operation rules to mitigate those changes. For this purpose, an integrated model is used, including a hydrological model of the Vesdre watershed, a hydraulic model of this river, a model of the dam complex operation rules and a flood risk model. Performance indicators of the dams are defined, representing drinking water production, damages due to floods, hydropower production and low-flow enrichment. First, a sensitivity analysis of the main parameters of the dam operation rules on the performance indicators is achieved. Afterwards, for two extreme climate scenarios at the time horizons 2021-2050 and 2071-2100, impacts of climate change on the reservoir performances are determined. Then, the results of the sensitivity analysis are used to indicate if climate change impacts may be mitigated by means of enhanced operation rules. [less ▲] Detailed reference viewed: 72 (37 ULg)Experimental parametric study and design of Piano Key Weirs ; Pirotton, Michel ; Archambeau, Pierre et al in Journal of Hydraulic Research (2014), 52(3), 326-335 Piano Key Weirs are an effective solution for dam rehabilitation as well as new dam projects with a high level of hydraulic constraints. In order to improve the efficiency of their design, an experimental ... [more ▼] Piano Key Weirs are an effective solution for dam rehabilitation as well as new dam projects with a high level of hydraulic constraints. In order to improve the efficiency of their design, an experimental study of the influence of the main geometric parameters has been performed. Thirty one configurations were tested for a wide range of discharges. The results of the study show the influence of the weir height, the keys widths and the overhangs lengths on the discharge capacity and flow characteristics. Based on hydraulic considerations, optimum values of the main geometric ratios are provided. An analytical formulation is developed to predict the discharge capacity of the weir as a function of its geometry. It shows an accuracy of 10% compared to the experimental results of this study and from other sources. [less ▲] Detailed reference viewed: 61 (8 ULg)MAT_LSPIV 4.0: User Manual Peltier, Yann ; Dewals, Benjamin ; Erpicum, Sébastien et al Software (2014) Detailed reference viewed: 68 (14 ULg)Meandering jets in shallow rectangular reservoir Peltier, Yann ; Erpicum, Sébastien ; Archambeau, Pierre et al in 7th International Conference in River Hydraulics, River Flow 2014 (2014) In this article, meandering flows in a shallow rectangular reservoir are experimentally and numerically investigated. Two experiments were performed in a smooth shallow horizontal flume and the surface ... [more ▼] In this article, meandering flows in a shallow rectangular reservoir are experimentally and numerically investigated. Two experiments were performed in a smooth shallow horizontal flume and the surface velocity fields were measured by Large-Scale PIV (LSPIV). The flow conditions were chosen in such a way that the friction regime of both flows was different. These flows were then modelled using the academic code WOLF2D, which solves the 2D shallow water equations and uses a depth-averaged k- model for modelling turbulence. The main characteristics of the measured and simulated flows were finally extracted from a Proper Orthogonal Decomposition (POD) of the surface velocity fields and depth-averaged velocity fields respectively and were compared. When the mean fluctuating kinetic energy of the considered POD mode is greater than 1×10-5 m²/s², the numerical modelling and the experiments are in good agreement whatever the friction regime of the flow. [less ▲] Detailed reference viewed: 29 (11 ULg) |
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