References of "Pirotton, Michel"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailEnergy conservation properties of Ritter solution for idealized dam break flow
Dewals, Benjamin ULg; Bruwier, Martin ULg; Erpicum, Sébastien ULg et al

in Journal of Hydraulic Research (in press)

We examine different aspects of energy conservation in the case of the analytical solution of Ritter for idealized dam break flow in a horizontal frictionless and dry channel. We detail the application of ... [more ▼]

We examine different aspects of energy conservation in the case of the analytical solution of Ritter for idealized dam break flow in a horizontal frictionless and dry channel. We detail the application of the unsteady Bernoulli equation in this case and highlight that the inertial effects cancel out when averaged over the whole flow region. We also show that the potential and kinetic contributions to the total mechanical energy in the flow region have a distinct and constant relative importance: potential energy accounts for 60 %, and kinetic energy for 40 % of the total mechanical energy. These properties of Ritter solution are rarely emphasized while they may be of practical relevance, particularly for the verification of numerical schemes with respect to their ability to ensure energy conservation. [less ▲]

Detailed reference viewed: 50 (27 ULg)
Full Text
Peer Reviewed
See detailEvaluation et gestion des scenarii de dysfonctionnement des barrages-réservoirs en Belgique
Liégeois, Benoît; Pirotton, Michel ULg; Dewals, Benjamin ULg et al

in Sûreté des barrages et enjeux (2016, November)

Belgium has fifteen structures included in the list of large dams of the International Committee on Large Dams. Six are managed by Engie Company, the other nine are owned by the Walloon regional public ... [more ▼]

Belgium has fifteen structures included in the list of large dams of the International Committee on Large Dams. Six are managed by Engie Company, the other nine are owned by the Walloon regional public authority. The Belgian legislator has never enacted specific rules for large dams. However, managers have always been concerned with this issue. They developed procedures and methods that were subject to exchanges of experience with their counterparts, in particular through the Belgian Committee on Large Dams. In this ongoing research of security, the impact of multiple failure scenarios (dam break, quick emptying …) on the people and the environment downstream of dams is a particular focal point. An impact study has been conducted for the main plants. This study is based on a deterministic numerical method. The methodology, the assumptions regarding the failure mode or emptying and the lessons learned from the analyses are presented. These results are an important step in the assessment and the management of risks. Indeed, regulations were recently enacted for the management and the coordination of any activity likely to seriously impact public safety during crisis periods. These rules apply therefore for large dams. In this context, managers have established an emergency plan for each structure. This paper provides a broad overview on the issues of the evaluation and the management of dysfunction risks of Belgian dams, as well as on approaches and collaborations initiated between the private managers and public authority. [less ▲]

Detailed reference viewed: 6 (1 ULg)
Full Text
Peer Reviewed
See detailMonitoring topography of laboratory fluvial dike models subjected to breaching based on a laser profilometry technique
Rifai, Ismail ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in International Symposium on River Sedimentation: Stuttgart 19th-22d september 2016 (2016, September)

Detailed reference viewed: 31 (14 ULg)
Full Text
Peer Reviewed
See detailSensitivity of the breaching process in the case of overtopping induced fluvial dike failure
Rifai, Ismail ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in River Flow 2016 Proceedings (2016, July)

Fluvial dikes are common structures constructed for flow channelization, prevention of river bed lateral migration and for flood protection purposes. Their aging increases their vulnerability to extreme ... [more ▼]

Fluvial dikes are common structures constructed for flow channelization, prevention of river bed lateral migration and for flood protection purposes. Their aging increases their vulnerability to extreme hydro-logical events, and subsequently may cause their failure. Many laboratory studies of overtopping induced dike failure were conducted, dealing mainly on normal configurations (i.e. dam break configuration) without ac-counting for the influence of a parallel flow. The fluvial dike breaching process remains, therefore, insuffi-ciently studied. A simplified model assuming a parameterized evolution of the breach geometry has been de-veloped to evaluate the fluvial breaching process. Results showed a sensitivity of the breaching process to the main channel configuration and to the flow conditions. Also, the evolution mode that was prescribed for the breach cross-section strongly influences the breaching duration and the sediment discharge [less ▲]

Detailed reference viewed: 23 (7 ULg)
Full Text
Peer Reviewed
See detailNappe Vibration Mitigation Techniques for Free-overfall Structrures
Lodomez, Maurine ULg; Crookston, Brian M.; Tullis, Blake P. et al

in Full Proceedings: Hydraulic Structures and Water System Management (2016, June 27)

Nappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow hydraulic structures operating at low heads, such as fountains, crest gates, and weirs. This ... [more ▼]

Nappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow hydraulic structures operating at low heads, such as fountains, crest gates, and weirs. This phenomenon is visually characterized by oscillations in the thin nappe cascading downstream of the control structure. These oscillations can produce a significant level of noise and acoustic pressure waves, which can increase the environmental and societal impacts of the hydraulic structure. As a result, a detailed investigation has been undertaken to identify practical and effective mitigation solutions for free-overfall structures where nappe vibration may be of concern. Research is being performed with a prototype-scale linear weir (weir length of 3.5 m and fall height of 3 m) located at the Engineering Hydraulics laboratory of the University of Liège, to assess the effectiveness of various crest modifications and any corresponding impacts to hydraulic efficiency (i.e., flow rate). The test matrix includes the optimization (position and spacing of elements) of three mitigation solutions which are projecting bolts, deflectors and step. In addition, a high-speed camera and audio equipment have been used to evaluate effectiveness of the configurations in reducing nappe vibration. Finally, this practical study has identified countermeasures suitable for retrofits and new construction, easy to construct, durable, hydraulically efficient, and with minimal potential for debris collection. [less ▲]

Detailed reference viewed: 13 (4 ULg)
Full Text
Peer Reviewed
See detailDistribution of uncertainties at the municipality level for flood risk modelling along the river Meuse: implications for policy-making
Pirotton, Michel ULg; Stilmant, Frédéric; Erpicum, Sébastien ULg et al

Conference (2016, April)

Flood risk modelling has been conducted for the whole course of the river Meuse in Belgium. Major cities, such as Liege (200,000 inh.) and Namur (l 10,000 inh.), are located in the floodplains of river ... [more ▼]

Flood risk modelling has been conducted for the whole course of the river Meuse in Belgium. Major cities, such as Liege (200,000 inh.) and Namur (l 10,000 inh.), are located in the floodplains of river Meuse. Particular attention has been paid to uncertainty analysis and its implications for decision-making. The modelling chain contains flood frequency analysis, detailed 2D hydraulic computations, damage modelling and risk calculation. The relative importance of each source of uncertainty to the overall results uncertainty has been estimated by considering several alternate options for each step of the analysis; different distributions were considered in the flood frequency analysis; the influence of modelling assumptions and boundary conditions (e.g., steady vs. unsteady) were taken into account for the hydraulic computation; two different landuse classifications and two sets ofdamage functions were used; the number of exceedance probabilities involved in the risk calculation (by integration of the risk-curves) was varied. In addition, the sensitivity of the results with respect to increases in flood discharges \vas assessed. The considered increases are consistent with a "wet" climate change scenario for the time horizons 202l~2050 and 2071-2100 (Detrembleur et al., 2015). The results of hazard computation differ significantly between the upper and lower parts of the course of river Meuse in Belgium. In the former, inundation extents grow gradually as the considered flood discharge is increased (i.e. the exceedance probability is reduced), while in the downstream part, protection structures (mainly concrete walls) prevent inundation for flood discharges corresponding to exccedance probabilities of 0.01 and above (in the present climate). For higher discharges, large inundation extents are obtained in the floodplains. The highest values of risk (mean annual damage) are obtained in the municipalities which undergo relatively frequent flooding (upper part of the river), as well as in those of the downstream part of the Meuse in which flow depths in the urbanized floodplains are particularly high when inundation occurs. This is the case of the city of Liege, as a result of a subsidence process following former mining activities. For a given climate scenario, the uncertainty ranges affecting flood risk estimates are significant; but not so much that the results for the different municipalities would overlap substantially. Therefore, these uncertainties do not hamper prioritization in terms of allocation of risk reduction measures at the municipality level. In the present climate, the uncertainties arising from flood frequency analysis have a negligible influence in the upper part of the river, while they have a considerable impact on risk modelling in the lower part, where a threshold effect was observed due to the flood protection structures (sudden transition from no inundation to massive flooding when a threshold discharge is exceeded). Varying the number of exceedance probabilities in the integration of the risk curve has different effects for different municipalities; but it does not change the ranking of the municipalities in terms of flood risk. For the other scenarios, damage estimation contributes most to the overall uncertainties. As shown by this study, the magnitude of the uncertainty and its main origin vary in space and in time. This emphasizes the paramount importance of conducting distributed uncertainty analyses. In the considered study area, prioritization of risk reduction means can be reliably performed despite the modelling uncertainties. [less ▲]

Detailed reference viewed: 27 (4 ULg)
Full Text
Peer Reviewed
See detailThe contribution of air-fluidization to the mobility of rapid flowslides
Stilmant, Frédéric; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

Conference (2016, April)

Air-fluidization can be the origin of the long runout of gravitational flows involving fine particles such as ash. An excessive air pore pressure dramatically reduces the friction angle of the material as ... [more ▼]

Air-fluidization can be the origin of the long runout of gravitational flows involving fine particles such as ash. An excessive air pore pressure dramatically reduces the friction angle of the material as long as this pressure has not been dissipated, which occurs during the flow. This phenomenon can be modelled thanks to the 2D depth-averaged equations of mass and momentum conservation and an additional transport equation for basal pore pressure evolu- tion (Iverson and Denlinger, 2001). ln this contribution, we discuss the application of this model in relation to recent experimental results on air- fluidized flows by Roche et al. (2008) and Roche (2012). The experimental results were used to set a priori the value of the diffusion coefficient in the model, taking into account the diference of scale between the experiments and real-world applications. We also compare the model predictions against detailed observations of a well-documented historical event, the collapse of a fly-ash heap in Belgium (Stilmant et al., 2015). In particular, we analyse the influence of the different components of the model on the results (pore pressure dissipation vs. pore pressure generation). The diffusion coefficient which characterizes the dissipation of air pore pressure is found sufficiently low for maintaining a fluidized flow over hundreds of meters. The study concludes that an air-tluidization theory is consistent with the field observations. These findings are particularly interesting as they seem not in line with the mainstream acceptation in landslide modelling that air generally plays a secondary role (e.g., Legros, 2002). [less ▲]

Detailed reference viewed: 19 (1 ULg)
Full Text
Peer Reviewed
See detailContribution of future urbanisation expansion to flood risk changes
Bruwier, Martin ULg; Mustafa, Ahmed; Archambeau, Pierre ULg et al

Conference (2016, April)

The flood risk is expected to increase in the future due to climate change and urban development. Climate change modifies flood hazard and urban development influences exposure and vulnerability to floods ... [more ▼]

The flood risk is expected to increase in the future due to climate change and urban development. Climate change modifies flood hazard and urban development influences exposure and vulnerability to floods. While the influence of climate change on flood risk has been studied widely, the impact of urban development also needs to be considered in a sustainable flood risk management approach. The main goal of this study is the determination of the sensitivity of future flood risk to different urban devel~ opment scenarios at a relatively short-time horizon in the River Meuse basin in Wallonia (Belgium). From the different scenarios, the expected impact of urban development on flood risk is assessed. Three urban expansion scenarios are developed up to 2030 based on a coupled cellular automata (CA) and agent-based (AB) urban expansion model: (i) business-as-usual, (ii) restrictive and (m) extreme expansion scenarios. The main factor controlling these scenarios is the future urban land demand. Each urban expansion scenario is developed by considering or not high and/or medium flood hazard zones as a constraint for urban development. To assess the model's performance, it is calibrated for the Meuse River valley (Belgium) to simulate urban expansion between i990 and 2000. Calibration results are then assessed by comparing the 2000 simulated land-use map and the actual 2000 land-use map. The flood damage estimation for each urban expansion scenario is determined for five flood discharges by overlaying the inundation map resulting from a hydraulic computation and tlte urban expansion map and by using damage curves and specific prices. The hydraulic model Wolt‘2D has been extensively validated by comparisons between observations and computational results during flood event .This study focuses only on mobile and immobile prices for urban lands, which are associated to the most severe damages caused by floods along the River Meuse. These findings of this study offers tools to drive urban expansion based on numerous policies visions to mitigate future flood risk along the Meuse River. In particular, we assess the impacts on future flood risk of the prohibition of urban development in high and/or medium flood hazard zones. [less ▲]

Detailed reference viewed: 63 (11 ULg)
Peer Reviewed
See detailWhen the same hydraulics conditions lead to different depositional patterns: case of an idealised delta
Peltier, Yann; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Geophysical Research Abstracts (2016, April)

Deltas are complex hydrosystems and ecosystems resulting from the interactions of a river system with a water body almost at rest. Anthropogenic factors (hydropower, flood management, development in the ... [more ▼]

Deltas are complex hydrosystems and ecosystems resulting from the interactions of a river system with a water body almost at rest. Anthropogenic factors (hydropower, flood management, development in the floodplains) lead to dramatic changes in sediment transport in the rivers and in sediment management practice. From continuous, the sediment transport becomes increasingly intermittent, with long periods of deficit in the sediment supply and short periods characterized by large supplies. Understanding how these intermittencies in the sediment supply affect the delta morphodynamics is of paramount importance for predicting the possible evolution and functioning of deltas. Deltas can reasonably be idealised as a reservoir, with an inlet channel representing the river and the sud- den enlargement of the reservoir representing the water body at rest. Using such an ideal configuration enables the assessment of the influence of individual geometric and hydraulic parameters on the depositional patterns responsible for the morphodynamic evolution of the delta. Recent literature has shown that for very similar hydraulic boundary conditions, two very different types of flow fields may develop (“straight jet” vs. “meandering jet”), leading to totally different depositional patterns. In turn, these distinct depositional patterns affect the flow itself through a two-way coupling between the hydrodynamics and the morphodynamics of the deposits. These complex processes will be discussed in the proposed presentation, based on the results of over 160 experimental tests and corresponding numerical simulations. [less ▲]

Detailed reference viewed: 28 (2 ULg)
Full Text
Peer Reviewed
See detailEffective soil hydraulic conductivity predicted with the maximum power principle
Westhoff, Martijn ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2016, April)

Drainage of water in soils happens for a large extent through preferential flowpaths, but these subsurface flowpaths are extremely difficult to observe or parameterize in hydrological models. To ... [more ▼]

Drainage of water in soils happens for a large extent through preferential flowpaths, but these subsurface flowpaths are extremely difficult to observe or parameterize in hydrological models. To potentially overcome this problem, thermodynamic optimality principles have been suggested to predict effective parametrization of these (sub-grid) structures, such as the maximum entropy production principle or the equivalent maximum power principle. These principles have been successfully applied to predict heat transfer from the Equator to the Poles, or turbulent heat fluxes between the surface and the atmosphere. In these examples, the effective flux adapts itself to its boundary condition by adapting its effective conductance through the creation of e.g. convection cells. However, flow through porous media, such as soils, can only quickly adapt its effective flow conductance by creation of preferential flowpaths, but it is unknown if this is guided by the aim to create maximum power. Here we show experimentally that this is indeed the case: In the lab, we created a hydrological analogue to the atmospheric model dealing with heat transport between Equator and poles. The experimental setup consists of two freely draining reservoirs connected with each other by a confined aquifer. By adding water to only one reservoir, a potential difference will build up until a steady state is reached. From the steady state potential difference and the observed flow through the aquifer, and effective hydraulic conductance can be determined. This observed conductance does correspond to the one maximizing power of the flux through the confined aquifer. Although this experiment is done in an idealized setting, it opens doors for better parameterizing hydrological models. Furthermore, it shows that hydraulic properties of soils are not static, but they change with changing boundary conditions. A potential limitation to the principle is that it only applies to steady state conditions. Therefore the rate of adaptation of hydraulic properties should be faster than the rate of change in boundary conditions. [less ▲]

Detailed reference viewed: 16 (6 ULg)
Full Text
See detailImpacts of urban expansion on future flood damage: A case study in the River Meuse basin, Belgium
Mustafa, Ahmed; Bruwier, Martin ULg; Teller, Jacques ULg et al

in Erpicum, Sébastien; Dewals, Benjamin; Archambeau, Pierre (Eds.) et al Sustainable Hydraulics in the Era of Global Change: Advances in Water Engineering and Research (2016)

Detailed reference viewed: 35 (15 ULg)
Full Text
Peer Reviewed
See detailHydrodynamics of long-duration urban floods: experiments and numerical modelling
Arrault; Finaud-Guyot, Pascal; Archambeau, Pierre ULg et al

in Natural Hazards & Earth System Sciences (2016), 16

Flood risk in urbanized areas raises increasing concerns as a result of demographic and climate changes. Hydraulic modelling is a key component of urban flood risk analysis. Yet, detailed validation data ... [more ▼]

Flood risk in urbanized areas raises increasing concerns as a result of demographic and climate changes. Hydraulic modelling is a key component of urban flood risk analysis. Yet, detailed validation data are still lacking for comprehensively validating hydraulic modelling of inundation flow in urbanized floodplains. ln this study, we present an experimental model of inundation flow in a typical European urban district and we compare the experimental observations with predictions by a shallow-water numerical model. The setup is 5 ll\X Sm and involves seven streets along each direction, leading to 49 intersections. Different inflow discharges and flow partitions were tested. The performance ofthe numerical model is assessed and the upscaling ofthe experimental observations to the field is discussed. [less ▲]

Detailed reference viewed: 57 (19 ULg)
Full Text
Peer Reviewed
See detailTowards a New Design Equation for Piano Key Weirs Discharge Capacity
Bashiri Atrabi, Hamid ULg; Dewals, Benjamin ULg; Pirotton, Michel ULg et al

in Proc. of the 6th International Symposium on Hydraulic Structures (2016)

Piano Key weirs are Labyrinth like weirs which can be placed on the top of gravity dams. They represent a powerful solution to increase the discharge capacity of existing dam spillways. For proper design ... [more ▼]

Piano Key weirs are Labyrinth like weirs which can be placed on the top of gravity dams. They represent a powerful solution to increase the discharge capacity of existing dam spillways. For proper design it is necessary to accurately predict this discharge capacity. In this research, artificial neural network, multiple linear and nonlinear regressions are used to set up a new design equation for the discharge capacity of Piano Key weirs. The effect of each parameter on the discharge capacity of Piano Key weirs is tested in these models. Several non-dimensional parameters are used to define a functional relationship between the inputs and output. These parameters are built from the geometric dimensions of the structure such as weir height, inlet and outlet keys width, overhangs length, water head and side crest length. Previous experimental data, which were collected at the experimental laboratory of the research group Hydraulics in Environmental and Civil Engineering (HECE), University of Liege, are used for training and testing patterns of the models. Root mean square errors (RMSE) and coefficient of determination (R2) are used as comparing criteria for the evaluation of the models. The models’ results are compared with experimental results and other existing equations. [less ▲]

Detailed reference viewed: 43 (13 ULg)
Full Text
See detailErosion and sedimentation in a hydropower project: assessing impacts and opportunities
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

in Schüttrumpf, Holger (Ed.) Offene Gewässer: Strahlwirkung, Fischaufstieg, Fischabstieg, Sedimente, Schadstoffe (2016)

Detailed reference viewed: 23 (2 ULg)
Full Text
Peer Reviewed
See detailHydrodynamic instabilities in shallow reservoirs: implications for sediment management
Peltier, Yann; de Cuyper, Anaïs; Erpicum, Sébastien ULg et al

Conference (2016)

Detailed reference viewed: 24 (1 ULg)
Full Text
Peer Reviewed
See detailDiscretization of the divergence formulation of the bed slope term in the shallow-water equations and consequences in terms of energy balance
Bruwier, Martin ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Applied Mathematical Modelling (2016)

In this research, the influence on energy balance of the discretization scheme of the divergence formulation of the bed slope term in the shallow-water equations is analysed theoretically (for a single ... [more ▼]

In this research, the influence on energy balance of the discretization scheme of the divergence formulation of the bed slope term in the shallow-water equations is analysed theoretically (for a single topographic step) and based on two numerical tests. Different values of the main parameter controlling the discretization scheme of the divergence formulation are analysed to identify the formulation which minimizes the energy variation resulting from the discretization. For a wide range of ambient Froude numbers and relative step heights, the theoretical value of the control parameter minimizing the energy variation falls within a very narrow range, which can reasonably be approximated by a single “optimal” value. This is a result of high practical relevance for the design of accurate numerical schemes, as confirmed by the results of the numerical tests. [less ▲]

Detailed reference viewed: 38 (12 ULg)