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See detailModélisation spatialement distribuée et physiquement basée d’écoulements hydrologiques et hydrodynamiques pour l’aide à la gestion d’ouvrages hydrauliques
Khuat Duy, Bruno ULg

Doctoral thesis (2011)

La gestion des ressources en eau constitue une préoccupation qui prend une place de plus en plus importante dans nos sociétés. Les événements climatiques extrêmes subis ces dernières années (pluies ... [more ▼]

La gestion des ressources en eau constitue une préoccupation qui prend une place de plus en plus importante dans nos sociétés. Les événements climatiques extrêmes subis ces dernières années (pluies diluviennes mais également sécheresses) montrent toute la nécessité d’une meilleure compréhension des phénomènes en cause afin de mettre en place une gestion efficace des ressources. Ces études passent notamment par le développement de logiciels de simulation basés sur des modèles hydrologiques et hydrodynamiques fiables capables de représenter correctement les phénomènes réels mis en jeu. Cette thèse contribue à la mise en place d’un outil de modélisation spatialement distribuée et physiquement basée d’écoulements hydrologiques et hydrodynamiques, destiné notamment à fournir une aide précieuse pour la gestion d’ouvrages hydrauliques. Chaque composante de modélisation du circuit hydrologique, depuis la pluie jusqu’à l’exutoire de la rivière, est examinée. Des améliorations ou développements plus fondamentaux sont alors proposés pour améliorer la qualité de modélisation. Entre autres, cette thèse aborde en profondeur des sujets tels que la prise en compte de la microtopographie dans la représentation des phénomènes de surface (stockage dans les dépressions, écoulement en ruisselets, relations hauteurs-section-volume…), le calcul de l’infiltration (modèle à fronts multiples, effet de l’occupation du sol…) ou l’écoulement dans la couche hypodermique (écoulement saturé/non saturé, mise en pression…). Les recherches et développements portent également sur l’écoulement dans les axes de concentration (création d’un réseau de rivières cohérent à la fois avec le modèle numérique de terrain et les levés précis sur site, exploitation adéquate des données de section, modélisation efficace des ouvrages en charge ou non…). La modélisation des surfaces imperméables (avec séparation des zones égouttées ou non) est également abordée de façon détaillée, dans le cadre d’une application sur un bassin versant instrumenté de 130 km². Cette application envisage aussi bien la modélisation d’un événement ponctuel que des simulations à long terme. Enfin, l’étude d’un bassin peu instrumenté permet de montrer la large applicabilité et sa capacité à servir de support efficace dans la gestion des rivières et des ouvrages hydrauliques associés. [less ▲]

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See detailModelling of sewer systems as a component of a global hydrological model
Khuat Duy, Bruno ULg; Archambeau, Pierre ULg; Dewals, Benjamin ULg et al

in Proceedings of the 4th International Conference on Advanced Computational Methods in Engineering (2008)

Hydrology often takes an important place in the domain of hydraulic structures management, and is a key component of many hydraulic studies. Modelling the main hydrological processes requires a particular ... [more ▼]

Hydrology often takes an important place in the domain of hydraulic structures management, and is a key component of many hydraulic studies. Modelling the main hydrological processes requires a particular attention in order to deal with problems in an optimal way. Instrumented basins studies has pointed out the considerable impact of the sewer system on the hydrological outputs dynamics on small basins, even poorly urbanized. The current models often take into account the distributed impervious areas by adapting the corresponding surfaces runoff or infiltration coefficients. This approach, which is suited to produce correct runoff volumes, is however unable to represent the real flow outputs dynamics in which important variations can occur with a hourly time step. Modelling this flow component is essential to catch the rapidly-varying flow inputs generated by the runoff on drained impervious areas. An efficient modelling method has therefore been developed to include the sewer system in a global hydrological model (WOLF), using accurate landuse data in vector format and available data on the sewage system. These developments have been successfully tested on the Berwinne basin, Belgium. [less ▲]

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See detailModern techniques for flood risk analysis: quasi-3D simulations in a GIS environment
Archambeau, Pierre ULg; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

in Geophysical Research Abstracts (2005), 7(09348),

Human beings have continuously attempted to adapt their environment to their needs. However, many natural phenomena still remain challenging to control and the populations must undergo sometimes heavily ... [more ▼]

Human beings have continuously attempted to adapt their environment to their needs. However, many natural phenomena still remain challenging to control and the populations must undergo sometimes heavily damaging consequences. It is consequently essential to study these phenomena in order to assess their potential hazards. In particular, the scope of the present paper focus on floods. The intense floods met these last years showed the importance of this phenomenon as well as its many devastating effects. Thanks to recent important breakthroughs, both in the field of conceptual and numerical modelling of complex flows and in the calculation power of computers, it is henceforth possible to study the effects of potential floods on the basis of numerical simulations, with an accuracy never reached beforehand. The Laboratory of Applied Hydrodynamics and Hydraulic Constructions (HACH) of the University of Liege has always made this kind of study one of its core competencies, thanks to • the development of modern and powerful modelling tools (quasi-three dimensional software for flow simulation by finite volume), • the use of a broad range of data enabling a proper representation of the studied fields (topography, occupation of the ground...) • the systematic validation of simulation results. These tools are currently intensively used within the framework of a general study of the flood-prone zones of the Walloon area of Belgium, which corresponds to more than 800 km of rivers. [less ▲]

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See detailModelling suspended load with moment equations and linear concentration profiles
Khuat Duy, Bruno ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Raghay, S.; Ouazar, D.; Benkhaldoun, F. (Eds.) Finite volumes for complex applications (2005)

In numerical simulations, it is always necessary to find an optimum between the simplicity of the model and a good representation of real phenomena. In the field of hydraulic flows simulations, the models ... [more ▼]

In numerical simulations, it is always necessary to find an optimum between the simplicity of the model and a good representation of real phenomena. In the field of hydraulic flows simulations, the models using depth-averaged and moment equations are an interesting compromise between full 3D and simple depth-averaged models. This paper presents the use of a moment equation for suspended load transport. A simple but representative model for the sediment concentration profiles is developed. This original bi-linear concentration profile is compared to the traditional Rouse-profiles and shows a good correspondence despite its great simplicity. Advective and diffusive sediment fluxes are developed analytically and lead to a concise formulation, which is an asset for practical use. A differential equation for the sediment concentration moment is also fully developed, and a special attention is cast to the source term. The finite volume scheme has been chosen to implement the model, because it is particularly well suited for highly advective transport equations, it is conservative and it makes the choice of the upwinding easier. 1D simulations show the capacity of the model to reproduce laboratory experiments described in the literature. [less ▲]

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See detailModelling suspended load transport with linear concentration profiles
Khuat Duy, Bruno ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Proceedings of the 8th International Conference on Fluvial Sedimentology (2005)

In numerical simulations, it is always necessary to find an optimum between the simplicity of the model and a good representation of real phenomena. In the field of hydraulic flows simulations, the models ... [more ▼]

In numerical simulations, it is always necessary to find an optimum between the simplicity of the model and a good representation of real phenomena. In the field of hydraulic flows simulations, the models using depth-averaged and moment equations are an interesting compromise between full 3D and simple depth-averaged models. This paper presents the use of a moment equation for suspended load transport. A simple but representative model for the sediment concentration profiles is developed. This original bi-linear concentration profile is compared to the traditional Rouse-profiles and shows a good correspondence despite its great simplicity. Advective and diffusive sediment fluxes are developed analytically and lead to a concise formulation, which is an asset for practical use. A differential equation for the sediment concentration moment is also fully developed, and a special attention is cast to the source term. The finite volume scheme has been chosen to implement the model, because it is particularly well suited for highly advective transport equations, it is conservative and it makes the choice of the upwinding easier. 1D simulations show the capacity of the model to reproduce laboratory experiments described in the literature. [less ▲]

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See detailNumerical modelling with Wolf2D of the sedimentation problem at the entrance of a lock on the river Meuse
Khuat Duy, Bruno ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Dick, Erik; Hogge, Michel; Van Keer, Roger (Eds.) Proceedings of the 3rd International Conference on Advanced Computational Methods in Engineering (2005)

This paper presents the resolution of a practical hydraulic engineering problem thanks to effective numerical tools. A sedimentation study of the lock of Hun (river Meuse, Belgium) is completed using ... [more ▼]

This paper presents the resolution of a practical hydraulic engineering problem thanks to effective numerical tools. A sedimentation study of the lock of Hun (river Meuse, Belgium) is completed using solid transport models integrated in a finite volume free surface flows solver. The silting of the lock entrance is successfully modelled and various layout modifications of the site are tested to predict their effects and to see to what extent they could improve the actual situation. The analysis of the results shows that a regular dredging of the lock entrance is ineluctable. [less ▲]

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