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Can meandering flows in shallow rectangular reservoir be modelled with the 2D shallow water equations? Peltier, Yann ; Erpicum, Sébastien ; Archambeau, Pierre et al in Journal of Hydraulic Engineering (2015) In this article, the ability of the 2D shallow water equations to model meandering flows in shallow rectangular reservoirs is discussed. Four meandering flows, of various shallowness, were modelled using ... [more ▼] In this article, the ability of the 2D shallow water equations to model meandering flows in shallow rectangular reservoirs is discussed. Four meandering flows, of various shallowness, were modelled using the academic flow model WOLF 2D, which includes a depth-averaged k- model accounting for the horizontal and vertical turbulent length-scales. The bottom friction was modelled with the Colebrook-White formula and different roughness heights were considered. A Proper Orthogonal Decomposition (POD) was applied to the simulation results to extract the behaviour of the main structures responsible for the meandering flow. The same POD analysis was also performed for the reference experimental flow fields, obtained by Large-Scale Particle Image Velocimetry. The first two POD modes obtained from the numerical simulations assuming a smooth bottom are in good agreement with the experimental modes in terms of energy, as well as temporal and spatial variations, whatever the shallowness. In contrast, the remaining simulated modes are not well rendered. The effect of an increased roughness height in the simulations is finally discussed. It leads to an improved reproduction of the first two modes and of the following modes, except when significant viscous effects govern in the flow. [less ▲] Detailed reference viewed: 94 (42 ULg)Se barricader : une solution insuffisante face à l'eau ; Archambeau, Pierre ; Erpicum, Sébastien et al Article for general public (2014) Detailed reference viewed: 23 (4 ULg)Integrated catchment analysis in the Meuse basin for assessing water resources and future flood risk Dewals, Benjamin ; Archambeau, Pierre ; Bruwier, Martin et al Conference (2014, November 12) Detailed reference viewed: 21 (5 ULg)Potential damping of extreme floods in the river Meuse (Phase I): 1st progress report Bruwier, Martin ; Archambeau, Pierre ; Erpicum, Sébastien et al Report (2014) Detailed reference viewed: 22 (7 ULg)Prediction of mean and turbulent kinetic energy in rectangular shallow reservoirs ; Erpicum, Sébastien ; Archambeau, Pierre et al in Engineering Applications of Computational Fluid Mechanics (2014), 8(4), Shallow rectangular reservoirs are common structures in urban hydraulics and river engineering. Despite their simple geometry, complex symmetric and asymmetric flow fields develop in such reservoirs ... [more ▼] Shallow rectangular reservoirs are common structures in urban hydraulics and river engineering. Despite their simple geometry, complex symmetric and asymmetric flow fields develop in such reservoirs, depending on their expansion ratio and length-to-width ratio. The original contribution of this study is the analysis of the kinetic energy content of the mean flow, based on UVP velocity measurements carried throughout the reservoir in eleven different geometric configurations. A new relationship is derived between the specific mean kinetic energy and the reservoir shape factor. For most considered geometric configurations, leading to four different flow patterns, the experimentally observed flow fields and mean kinetic energy contents are successfully reproduced by an operational numerical model based on the depth-averaged flow equations and a two-length-scale k-e turbulence closure. The analysis also highlights the better performance of this depth-averaged k-e model compared to an algebraic turbulence model. Finally, the turbulent kinetic energy in the reservoir is derived from the experimental measurements and the corresponding numerical predictions based on the k-e model agree satisfactorily in the main jet but not in the recirculation zones. [less ▲] Detailed reference viewed: 56 (7 ULg)Hydrological and hydraulic modelling in environmental and civil engineering Dewals, Benjamin ; Erpicum, Sébastien ; Archambeau, Pierre et al Conference (2014, October 06) Detailed reference viewed: 32 (9 ULg)Landuse change and future flood risk: the influence of micro-scale spatial patterns (FloodLand) - 2nd 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: 85 (38 ULg)Velocity and turbulence measurements for assessing the stability of riverbeds: a comparison between UVP and ADVP Duma, Diana ; Erpicum, Sébastien ; Archambeau, Pierre et al in 11th International Conference on Hydroscience & Engineering - "Hydro-Engineering for Environmental Challenges" (2014, October) Maintaining the overall stability of active riverbeds requires a deep understanding of the complex interactions between turbulent flow forces and forces stabilizing the riverbed. Standard approaches do ... [more ▼] Maintaining the overall stability of active riverbeds requires a deep understanding of the complex interactions between turbulent flow forces and forces stabilizing the riverbed. Standard approaches do not properly take into account the turbulence fluctuations in non-uniform flows, while these are of primary importance in the mechanisms determining the stability of stones. In a new approach, the flow forces are quantified by means of parameters combining explicitly the velocity and turbulence distributions over a certain water depth above the riverbed. In this paper, as an onset for using these newly developed bed stability parameters, we report on new experimental measurements of velocity and turbulent kinetic energy based on acoustic methods, whereas all previous uses at the new bed stability parameters relied on Laser PIV Techniques. For quasi-uniform and non-uniform flow conditions, velocity measurements were conducted with two complementary devices: an ultrasonic velocimeter probe (UVP) and an acoustic Doppler velocimeter profiler (ADVP). The results are compared and discussed in detail. A general consistency between the two types of measurements is obtained, while some discrepancies are highlighted close to the bed and tentative explanations are given. [less ▲] Detailed reference viewed: 59 (12 ULg)Towards enhanced estimates of future water demand in the Meuse basin Dewals, Benjamin ; Archambeau, Pierre ; Erpicum, Sébastien et al Conference (2014, September 18) Detailed reference viewed: 8 (2 ULg)Flow and turbulence characterization as an onset for assessing the stability of gravel beds Duma, Diana ; Erpicum, Sébastien ; Archambeau, Pierre et al in 7th International Conference on Fluvial Hydraulics (2014, September) The flow characteristics, such as velocity profiles and turbulence intensities, are of high practical relevance in the assessment of riverbed stability. So far, the Shields diagram remains the most widely ... [more ▼] The flow characteristics, such as velocity profiles and turbulence intensities, are of high practical relevance in the assessment of riverbed stability. So far, the Shields diagram remains the most widely accepted approach for defining the initiation of sediment motion. However, it faces a number of shortcomings. In principle, it is only valid for uniform flow conditions and, under non-uniform flow conditions, it fails to account properly for the influence of turbulence in sediment entrainment. In this paper, we focus on a more detailed description of quasi-uniform and non-uniform flow characteristics in the vicinity of the critical flow conditions for inception of motion of gravel beds. Laboratory experiments were designed, involving two configurations. First, the entire bottom of the flume was paved with stones of uniform diameter (8 or 15 mm), leading to quasi-uniform flow conditions. Second, the flume bottom was smooth upstream of the zone of measurement while the downstream part was covered with gravels, leading to a sudden smooth-to-rough transition. The flow velocity was obtained by acoustic measurements and the turbulence intensity was calculated for both configurations. By fitting the velocity profile to a modified logarithmic law, the shear velocity was estimated. Standard approaches for predicting the threshold of motion, initially developed for uniform flows, were compared to other methods, based on depth-averaged turbulence kinetic energy, recently proposed in literature for non-uniform flow conditions. [less ▲] Detailed reference viewed: 65 (6 ULg)Towards enhanced estimates of future water demand in the Meuse basin: literature review ; Bruwier, Martin ; Archambeau, Pierre et al Report (2014) With respect to water management in the Meuse basin, the hydrological consequences of climate change have been taken into account in several studies so far; but this is not the case of many other ... [more ▼] With respect to water management in the Meuse basin, the hydrological consequences of climate change have been taken into account in several studies so far; but this is not the case of many other environmental and socio-economic changes, including trends in future water demand. The objective of this report is to serve as an onset for the development of a first approach to estimate at a relatively large-scale future water demand in the Meuse basin. Based on a review of recent literature, this report discusses the key drivers which influence water demand, with the aim of identifying the most suitable methods to implement in a subsequence more detailed analysis, as well as to highlight the data needs. [less ▲] Detailed reference viewed: 36 (14 ULg)La Meuse au fil des crues ; Dewals, Benjamin ; Archambeau, Pierre et al Article for general public (2014) Detailed reference viewed: 24 (5 ULg)Comparison between Experimental and SPH Models over a Sharp-crested Weir Lodomez, Maurine ; Erpicum, Sébastien ; Dewals, Benjamin et al Scientific conference (2014, August 28) In this paper the numerical simulations of a free surface flow over a sharp-crested weir are presented and compared to experimental results. The numerical model implemented consists of the meshless ... [more ▼] In this paper the numerical simulations of a free surface flow over a sharp-crested weir are presented and compared to experimental results. The numerical model implemented consists of the meshless Smoothed Particle Hydrodynamics (SPH) method which uses Navier-Stokes equations and the Tait equation of state for water. This numerical method has been developed in the framework of a master thesis and aimed to define the characteristics of the free jet. The validation of the results was performed through the analysis of the pressure field and the comparison of the numerical free surface profiles with experimental measurements conducted in the Hydraulic Laboratory of the University of Liège (ULg). A good qualitative agreement has been obtained. [less ▲] Detailed reference viewed: 34 (10 ULg)How to simulate quickly and efficiently a flow over a spillway ? Goffin, Louis ; Erpicum, Sébastien ; Dewals, Benjamin et al Conference (2014, August) Flows over hydraulic structures, such as weirs or spillways, can be modelled using different techniques. New models such as SPH or PFEM are becoming more and more popular. These models are particle and/or ... [more ▼] Flows over hydraulic structures, such as weirs or spillways, can be modelled using different techniques. New models such as SPH or PFEM are becoming more and more popular. These models are particle and/or meshless and consequently require a lot of computational power. Other methods such as VOF also require a lot of computational time. In the frame of 2-D vertical flows, other techniques use much less computation time. For irrotationnal flows, solving the Laplace equation can be done very efficiently. The difficulty of this method lies in the definition of boundary conditions. The free-surface, which is naturally determined when using Lagrangian methods, needs a heavy iterative solving due to its non-linear nature when expressed in the frame of the Laplace equation. This paper will present an original technique that allows a quicker and easier determination of the free-surface. An irregular mesh for boundaries is used and discussed. The method is validated with analytical solutions and experimental measurements. [less ▲] Detailed reference viewed: 62 (22 ULg)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 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: 36 (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: 23 (3 ULg) |
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