Le travail présenté concerne le développement d’un cadre d’applications pour le traitement d’écoulements dispersés, tenant compte de l’effet de la coagulation sur la distribution des tailles des particules. Nous explorons également quelques techniques de validation expérimentale. Les modèles sont valables pour un écoulement incompressible et isotherme, avec des particules qui ont un temps de relaxation faible en comparaison à celui du fluide. Pour la phase dispersée, une méthode eulérienne est utilisée, ce qui permet d’extrapoler la vitesse des particules de celle du fluide. La distribution des tailles est modélisée à l’aide du « Direct Quadrature Method of Moments ». Cette approche permet de résoudre des équations de transport pour les poids et les abscisses d’une approximation de la distribution à l’aide des fonctions Dirac delta. L’effet de la coagulation est pris en compte à l’aide d’un noyau de collisions qui utilise la vitesse instantanée du fluide. Toutes les équations de transport sont résolues à l’aide de la méthode des éléments finis. Pour le fluide, les stabilisations « Streamline Upwind » et « Pressure Stabilized Petrov-Galerkin » sont utilisées ensemble avec une stabilisation grad-div. Afin de limiter le temps de calcul pour une simulation directe, une formulation utilisant un traitement explicite des termes d’advection est proposée. Avec l’apparition de gradients élevés, les équations de transport pour les particules nécessitent une stabilisation supplémentaire. Tout le travail est disponible dans le projet de logiciel libre Coolfluid 3, en utilisant un langage spécifique permettant une implémentation directe pour des modèles en éléments finis. Le code qui en résulte ressemble à la forme variationnelle des équations utilisées. Le programme est générique en termes de dimensions spatiales et de type d’éléments. Une première validation utilise des résultats trouvés dans la littérature comme référence. La précision des méthodes est vérifiée à l’aide des vortices Taylor-Green. Pour l’écoulement et les concentrations des particules, une simulation directe d’un canal turbulent est effectuée. Le noyau de coagulation est vérifié à l’aide de particules de différentes tailles qui tombent à travers un vortex Burgers. Finalement, quelques techniques de validation expérimentale sont utilisées dans une cellule d’essai. La technique « Particle Image Velocimetry » est utilisée pour les vitesses du fluide, tandis que la distribution des tailles est mesurée à l’aide du « Phase Doppler Anemometry » et « Multiple Wavelength Light Extinction ». La technique d’extinction de lumière est capable de produire des distributions des tailles qui peuvent être comparées facilement avec les résultats numériques. / The present work deals with the development of a framework for the modeling of dispersed flows, including the effect of coagulation on the particle size distribution. We also explore some techniques for experimental validation. Models are developed for incompressible, isothermal flow containing particles that have a small relaxation time compared to the fluid time scale. For the dispersed phase, an equilibrium Eulerian approach is used, extrapolating the particle velocity from the fluid velocity. The size distribution is modeled using the Direct Quadrature Method of Moments. In practice, this results in solving transport equations for the weights and abscissa of a Dirac delta approximation of the size distribution. To model the effect of coagulation, a collision kernel that makes use of the resolved instantaneous velocity is developed. All transport equations are solved using the Finite Element Method. For the fluid, the Streamline Upwind and Pressure Stabilized Petrov-Galerkin method are used, with additional grad-div stabilization. To decrease the solution time for DNS, a segregated formulation with an explicit advection term is proposed. The particle transport equations require cross-wind diffusion in addition to the streamline upwind stabilization when large gradients occur. All work is available in the open source Coolfluid 3 framework, using an Embedded Domain Specific Language we developed for the implementation of finite element models. The resulting code closely resembles the variational form of the equations and is generic in terms of element type and the number of spatial dimensions. A first validation uses literature results as reference. Correctness and accuracy of the methods are verified using the Taylor-Green vortex flow. For the fluid and particle concentration, direct numerical simulation of a turbulent channel flow is performed. The particle coagulation kernel is tested using particles of different sizes falling through a Burgers vortex. Finally, some experimental validation techniques are used on a small test chamber. Particle image velocimetry is used for the fluid motion, while the size distributions are measured using Phase Doppler Anemometry and Multiple Wavelength Light Extinction. The light extinction technique was found to produce size distributions that could provide valuable reference data for our particle model.

Summer monsoon current (SMC) in the north Indian Ocean (NIO) is an open ocean current that flows eastward and enter into Bay of Bengal (BoB) during southwest monsoon (June–September). South of Sri Lanka, the SMC turns north-eastward instead of following eastward course and feeds into the BoB. Understanding the dynamics of SMC is crucial to understanding the interaction between Arabian sea (AS) and BoB. In the year 2009, the current moved north-eastward, meandered and then finally terminated into the southeast BoB. The northward bend of the current southeast of Sri Lanka has been attributed to the interaction of the eastward SMC with Rossby waves radiated from eastern boundary. An anticyclonic vortex formed right of the north-eastward meandering current which was associated with significantly high speeds. Reasons behind the unusually high speeds of SMC in this region remain unknown. Processes involved in the interaction of eddies with eastward SMC, the meandering of the current and its ultimate termination in southeast BoB are also not understood. Our study investigates the evolution, intensfication and meandering of SMC around Sri Lanka using an Indian Ocean general circulation model (MOM4p1) simulation for the year 2009. The model simulation, when compared with observational data OSCAR, showed good agreement. The study also explores the role of local and remote forcing in modulating the dynamics of SMC in the region. An eddy kinetic energy budget analysis for the region was performed which indicates the region to be a zone of significant eddy activity. Both barotropic, baroclinic instabilities were found to be the dominant mechanisms behind the generation of eddies. Based on eddy energetic analysis, the evolution of SMC was classified into stages i ii of onset, intensification, anticyclonic bend, anticyclonic vortices formation and meandering. Effect of eddies on mean flow were studied with the help of a transformed Eulerian mean (TEM) approach under quasi-geostrophic approximation. Eddy potential vorticity fluxes appearing in the TEM momentum equation and eddy enstrophy decay, divergence of eddy enstrophy advection from eddy enstrophy equation, helped to un-derstand when, where and how the eddies tended to drive the mean flow. Rossby waves and other westward propagating eddies arriving from the east, energise the SMC in June and induce an acceleration tendency on the mean flow through regions associated with upgradient eddy potential vorticity flux. In addition to the eddies, local winds also play a crucial role in driving the mean flow. Wind power, surface mean ocean kinetic energy and available potential energy (APE) were computed, integrated over the region of interest and compared to each other. The effect of local winds appear to be predominant in driving the mean flows as it not only increases the surface mean kinetic energy of the SMC but also raises the isopycnals and builds up large amount of APE in the ocean. Baroclinic instability takes place in late July and early August associated with the release of APE which flattens the isopycnals and thus weakens the SMC. Consequently the SMC meanders in course of time and flows into southeast BoB.

Heart disease is the leading cause of death in the world. Therefore, numerous studies are undertaken to identify indicators which can be applied to discover cardiac dysfunctions at an early age. Among others, the fluid dynamics of the blood flow (hemodymanics) is considered to contain relevant information related to abnormal performance of the heart.This thesis presents a robust framework for numerical simulation of the fluid dynamics of the blood flow in the left ventricle of a human heart and the fluid-structure interaction of the blood and the aortic leaflets.We first describe a patient-specific model for simulating the intraventricular blood flow. The motion of the endocardial wall is extracted from data acquired with medical imaging and we use the incompressible Navier-Stokes equations to model the hemodynamics within the chamber. We set boundary conditions to model the opening and closing of the mitral and aortic valves respectively, and we apply a stabilized Arbitrary Lagrangian-Eulerian (ALE) space-time finite element method to simulate the blood flow. Even though it is difficult to collect in-vivo data for validation, the available data and results from other simulation models indicate that our approach possesses the potential and capability to provide relevant information about the intraventricular blood flow.To further demonstrate the robustness and clinical feasibility of our model, a semi-automatic pathway from 4D cardiac ultrasound imaging to patient-specific simulation of the blood flow in the left ventricle is developed. The outcome is promising and further simulations and analysis of large data sets are planned.In order to enhance our solver by introducing additional features, the fluid solver is extended by embedding different geometrical prototypes of both a native and a mechanical aortic valve in the outflow area of the left ventricle.Both, the contact as well as the fluid-structure interaction, are modeled as a unified continuum problem using conservation laws for mass and momentum. To use this ansatz for simulating the valvular dynamics is unique and has the expedient properties that the whole problem can be described with partial different equations and the same numerical methods for discretization are applicable.All algorithms are implemented in the high performance computing branch of Unicorn, which is part of the open source software framework FEniCS-HPC. The strong advantage of implementing the solvers in an open source software is the accessibility and reproducibility of the results which enhance the prospects of developing a method with clinical relevance. / <p>QC 20171006</p>

[pt] Fluidos são extremamente comuns em nosso mundo e têm papel central em muitos fenômenos naturais. A compreensão de seu comportamento tem importância fundamental em uma vasta gama de aplicações e diversas áreas de pesquisa, da análise de fluxo sanguíneo até o transporte de petróleo, da exploração do fluxo de um rio até a previsão de maremotos, tempestades e furacões. Na simulação de fluidos, a abordagem conhecida como Euleriana é capaz de gerar resultados bastante corretos e precisos, mas as computações envolvidas podem se tornar excessivamente custosas quando há a necessidade de tratar fronteiras curvas e obstáculos com formas complexas. Este trabalho aborda esse problema e apresenta uma técnica Euleriana rápida e direta para simular o escoamento de fluidos em grades estruturadas parametrizadas tridimensionais. O principal objetivo do método é tratar de forma correta e eficiente as interações de fluidos com fronteiras curvas, incluindo paredes externas e obstáculos internos. Para isso, são utilizadas matrizes Jacobianas por célula para relacionar as derivadas de campos escalares e vetoriais nos espaços do mundo e paramétrico, o que permite a resolução das equações de Navier-Stokes diretamente no segundo, onde a discretização do domínio torna-se simplesmente uma grade uniforme. O trabalho parte de um simulador baseado em grades regulares e descreve como adaptá-lo com a aplicação das matrizes Jacobianas em cada passo, incluindo a resolução de equações de Poisson e dos sistemas lineares esparsos associados, utilizando tanto iterações de Jacobi quanto o método do Gradiente Biconjugado Estabilizado. A técnica é implementada na linguagem de programação CUDA e procura explorar ao máximo a arquitetura massivamente paralela das placas gráficas atuais. / [en] Fluids are extremely common in our world and play a central role in many natural phenomena. Understanding their behavior is of great importance to a broad range of applications and several areas of research, from blood flow analysis to oil transportation, from the exploitation of river flows to the prediction of tidal waves, storms and hurricanes. When simulating fluids, the so-called Eulerian approach can generate quite correct and precise results, but the computations involved can become excessively expensive when curved boundaries and obstacles with complex shapes need to be taken into account. This work addresses this problem and presents a fast and straightforward Eulerian technique to simulate fluid flows in three-dimensional parameterized structured grids. The method s primary design goal is the correct and efficient handling of fluid interactions with curved boundary walls and internal obstacles. This is accomplished by the use of per-cell Jacobian matrices to relate field derivatives in the world and parameter spaces, which allows the Navier-Stokes equations to be solved directly in the latter, where the domain discretization becomes a simple uniform grid. The work builds on a regular-grid-based simulator and describes how to apply Jacobian matrices to each step, including the solution of Poisson equations and the related sparse linear systems using both Jacobi iterations and a Biconjugate Gradient Stabilized solver. The technique is implemented efficiently in the CUDA programming language and strives to take full advantage of the massively parallel architecture of today s graphics cards.

Le développement d'outils de simulation efficaces demande d'appréhender à la fois la modélisation physique, la modélisation mathématique et la programmation informatique. Pour chacun de ces points, il est nécessaire de garder à l'esprit l'application visée, en effet le niveau de modélisation à adopter mais également les techniques de programmation à mettre en œuvre vont être différents selon l'utilisation que l'on envisage pour un code de calcul ou un logiciel de simulation.On commence dans ce travail de thèse par s'intéresser au niveau fin pour lequel on résout les équations d'Euler pour calculer un écoulement, on aborde ensuite la question de l'utilisation d'un code de calcul parallèle dans le contexte de la simulation d'un benchmark industriel. Enfin, on traite du niveau macroscopique associé à la simulation d'une installation industrielle complète pour lequel on utilise des relations phénoménologiques basées par exemple sur des corrélations expérimentales.Le premier chapitre traite de la détermination d'une vitesse de grille dans le contexte des méthodes ALE (Arbitrary Langrangian-Eulerian). Dans le chapitre suivant, on s’intéresse aux équations d'Euler compressibles résolues à l'aide de la méthode VFFC (Volumes Finis à Flux Caractéristiques), il s'agit d'introduire un modèle d'interface entre un fluide seul d'une part et un mélange homogène de deux fluides d'autre part, l'un des deux fluides ayant la même loi d'état que celui présent de l'autre côté de l'interface.Le troisième chapitre est consacré à la réalisation de simulations haute performance utilisant le code de calcul FluxIC basé sur la méthode VFFC avec capture d'interfaces, on s'intéresse plus particulièrement au phénomène de sloshing rencontré lors du transport de gaz naturel liquéfié par navire méthanier.Pour finir, le quatrième et dernier chapitre traite de la modélisation au niveau système d'une installation industrielle. On y présentera une approche systémique qui constitue un niveau de modélisation adapté à la simulation d'un grand nombre de composants et de leurs interactions. L'approche qui est présentée permet de concilier la modélisation de phénomènes physiques déterministes avec une modélisation stochastique visant à simuler, par exemple, le comportement de l'installation pour divers régimes de fonctionnement caractéristiques. / The development of efficient simulation tools requires an understanding of physical modeling, mathematical modeling and computer programming. For each of these domains it is necessary to bear in mind the intended application, because the use for a calculation code or simulation software will dictate the level of modeling, and also the programming techniques to be adopted.This dissertation starts with a detailed description applied in the form of fluid flow calculations using the Euler equations. Then simulation of an industrial benchmark is considered using a parallel computational method. Finally, simulation of a complete industrial plant is addressed, where phenomenological relations based on experimental correlations can be used.The first chapter deals with the determination of mesh velocity in the context of ALE (Arbitrary Lagrangian-Eulerian) methods. In the following chapter we focus on the compressible Euler equations solved using the FVCF method (Finite Volume with Characteristic Flux). In this case we consider an interface between a single fluid and a homogeneous two-fluid mixture, where one of the two mixed fluids and the single fluid have the same equation of state.The third chapter is devoted to running high performance simulations using the FluxIC computation code based on the FVCF method with interface capturing. The focus is on sloshing phenomenon encountered during transportation of Liquefied Natural Gas by LNG carriers.The fourth and final chapter deals with modeling of an industrial facility at system level. A systemic approach is presented that provides a level of modeling adapted to the simulation of a large number of components and their interactions. This approach enables users to combine deterministic modeling of physical phenomena with stochastic modeling in order to simulate the behavior of the system for a large set of operating conditions.

Les simulations dépendant du temps sont toujours un challenge dans l'industrie, notamment à cause des problèmes posés par les géométries mobiles en termes de CPU et de précision. Cette thèse présente des contributions à certains aspects des simulations en géométrie mobile. Un algorithme de bouger de maillage fondé sur une déformation de maillage sur un grand pas de temps et des changements de connectivité (swaps) est étudié. Une méthode d'élasticité et une méthode d'interpolation directe sont comparées en 3D, démontrant l'efficacité de l'algorithme. Cet algorithme est couplé à un solver ALE, dont les schémas et l'implémentation en 3D sont décrits en détail. Une interpolation linéaire est utilisée pou traiter les swaps. Des cas de validation montrent que les swaps n'influent pas notablement sur la précision de la solution. Plusieurs examples complexes en 3D démontrent la puissance de cette approche, pour des mouvement imposés ou pour des problèmes d'Interaction Fluide-Structure. L'adaptation de maillage anisotrope a démontré son efficacité pour améliorer la précision des calculs stationnaires pour un coût raisonnable. On considère l'extension de ces méthodes aux problèmes instationnaires, en mettant à jour l'algorithme de point fixe précédent grâce à une ananlyse de l'erreur espace-temps fondée sur le modèle de maillage continu. Une parallélisation efficace permet de réaliser des simulations adaptatives instationnaires avec une précision inégalée. Cet algorithme est étendu au cas des géométries mobiles en corrigeant la métrique optimale instationnaire. Finalement, plusieurs exemples 3D de simulations adaptatives en géométries mobiles démontrent l'efficacité de l'approche. / Time dependent simulations are still a challenge for industry, notably due to problems raised by moving boundaries, both in terms of CPU cost and accuracy. This thesis presents contributions to several aspects of simulations with moving meshes. A moving-mesh algorithm based on a large deformation time step and connectivity changes (swaps) is studied. An elasticity method and an Inverse Distance Weighted interpolation method are compared on many 3D examples, demonstrating the efficiency of the algorithm in handling large geometry displacement without remeshing. This algorithm is coupled with an Arbitrary-Lagrangian-Eulerian (ALE) solver, whose schemes and implementation in 3D are described in details. A linear interpolation scheme is used to handle swaps. Validation test cases showed that the use of swaps does not impact notably the accuracy of the solution, while several other complex 3D examples demonstrate the capabilities of the approach both with imposed motion and Fluid-Structure Interaction problems. Metric-based mesh adaptation has proved its efficiency in improving the accuracy of steady simulation at a reasonable cost. We consider the extension of these methods to unsteady problems, updating the previous fixed-point algorithm thanks to a new space-time error analysis based on the continuous mesh model. An efficient p-thread parallelization enables running 3D unsteady adaptative simulations with a new level of accuracy. This algorithm is extended to moving mesh problems, notably by correcting the optimal unsteady metric. Finally several 3D examples of adaptative moving mesh simulations are exhibited, that prove our concept by improving notably the accuracy of the solution for a reasonable time cost.

<div>Aluminum 6061 is extensively used in industry and welding and additive manufacturing (AM) of Al6061 offer flexibility in manufacturing. Solid-state welding and AM processes can overcome the shortcomings of fusion-based processes, such as porosity and hot cracking. In this thesis, friction stir welding and friction stir additive manufacturing, which are both based on the concepts of friction stir processing (solid-state), were studied. The welding parameters for a sound weld during friction stir welding of Al6061-T6 alloy were determined based on the experimental and numerical analysis. Formation of tunnel defects and cavity defects was also studied. A Coupled Eulerian-Lagrangian (CEL) finite element model was established to analyze the process, where the workpiece was modeled as an Eulerian body, and the tool as Lagrangian. The model was validated by conducting experiments and correlating the force measured by a three-axis dynamometer. The experimentally validated simulation model was used to find an optimum parameter set for the sound weld case.</div><div>To demonstrate the friction stir additive manufacturing process, a 40 mm × 8 mm × 8 mm (L×B×H) material was fabricated by adding five 1.6 mm thick plates. A similar coupled Eulerian-Lagrangian based finite element model was used to predict the effects of sound process parameters, such as the tool’s rotational speed and the translational speed. The temperature predicted by the model was used to predict the microhardness distribution in the sample and to further elucidate the hardness change in the weld zone, which showed a good agreement with the experimental results. The microstructure of the samples was analyzed, and the mechanical properties of the additive manufactured samples were characterized and compared with those of other AM techniques via tensile tests and tensile shear tests.</div>

The on-line condition monitoring of turbomachinery blades is of utmost importance to ensure the long term health and availability of such machines and as such has been an area of study since the late 1960s. As a result a number of on-line blade vibration measurement techniques are available, each with its own associated advantages and shortcomings. In general, on-blade sensor measurement techniques suffer from sensor lifespan, whereas non-contact techniques usually have measurement bandwidth limitations. One non-contact measurement technique that yields improvements in the area of measurement bandwidth is laser Doppler vibrometry. This thesis presents results and findings from utilizing laser Doppler vibrometry in an Eulerian fashion (i.e. a fixed reference frame) to measure on-line blade vibrations in axial-flow turbomachinery. With this measurement approach, the laser beam is focussed at a fixed point in space and measurements are available for the periods during which each blade sweeps through the beam. The characteristics of the measurement technique are studied analytically with an Euler-Bernoulli cantilever beam and experimental verification is performed. An approach for the numerical simulation of the measurement technique is then presented. Associated with the presented measurement technique are the short periods during which each blade is exposed to the laser beam. This characteristic yields traditional frequency domain signal processing techniques unsuitable for providing useful blade health indicators. To obtain frequency domain information from such short signals, it is necessary to employ non-standard signal processing techniques such as non-harmonic Fourier analysis. Results from experimental testing on a single-blade test rotor at a single rotor speed are presented in the form of phase angle trends obtained with non-harmonic Fourier analysis. Considering the maximum of absolute unwrapped phase angle trends around various reference frequencies, good indicators of blade health deterioration were obtained. These indicators were verified numerically. To extend the application of this condition monitoring approach, measurements were repeated on a five-blade test rotor at four different rotor speeds. Various damage cases were considered as well as different ELDV measurement positions. Using statistical parameters of the abovementioned indicators as well as time domain parameters, it is shown that with this condition monitoring approach, blade damage can successfully be identified and quantified with the aid of artificial neural networks. / Thesis (PhD)--University of Pretoria, 2010. / Mechanical and Aeronautical Engineering / unrestricted

Die künstliche Grundwasserabsenkung stellt eine wichtige Maßnahme für die Entwässerung von Baugruben und bergbaulich genutzten Flächen dar. Eine erfolgreiche und zielgerichtete Absenkung des Grundwasserspiegels setzt ein zweckmäßiges Design und die richtige Auswahl der genutzten Absenkungstechniken voraus. Dabei sind insbesondere die Dimension des abzusenkenden Bereichs, die Untergrundbeschaffenheit sowie zu erfüllende umweltschutzrechtliche Regelungen zu berücksichtigen. Zur Grundwasserabsenkung kommen üblicherweise verschiedene Ausführungen und Anordnungen von Pumpbrunnen zum Einsatz. Konventionelle Pumpbrunnen, welche für Absenkungsmaßnahmen eingesetzt werden, entnehmen Grundwasser aus dem Aquifer. Durch das fortwährende Abpumpen von in der Regel erheblichen Wassermengen können jedoch Umweltprobleme entstehen, und es ist mit zusätzlichen Entsorgungskosten für die Ableitung des geförderten Wassers zu rechnen. Im Gegensatz hierzu stellen vertikale Zirkulationsbrunnen (VCW) einen innovativen Ansatz dar, der eine lokale Grundwasserabsenkung ohne Nettowasserentnahme aus dem Aquifer erlaubt. Ein VCW kann als ein Einbohrlochsystem aufgefasst werden, bei dem im oberen Bereich eines Brunnens Wasser entnommen und dieses in einem separaten, weiter unten installierten Brunnenbereich wieder injiziert wird. Die erfolgreiche Anwendung dieser neuen Grundwasserabsenkungstechnik erfordert die genaue Kenntnis der Faktoren, welche für die Grundwasserströmungsverhältnisse relevant sind und somit die Absenkung bestimmen. Traditionelle Berechnungsansätze vernachlässigen oft vertikale Grundwasserbewegungen und sind deshalb für die Beschreibung der komplexen Strömungsverhältnisse in unmittelbarer Nähe eines VCW nicht geeignet. Aus diesem Grund steht die systematische Untersuchung der Grundwasserströmung unter Berücksichtigung vertikaler Strömungskomponenten im Hauptfokus dieser Arbeit. Die Untersuchungen beschäftigen sich in erster Linie mit der Entwicklung einer geeigneten Simulationsmethode, mit der Evaluierung des Einflusses relevanter hydrogeologischer Parameter sowie mit der Durchführung und Auswertung von Pumpversuchen an einem Feldstandort. Die hier vorgestellte neue Simulationsmethode koppelt den sogenannten Arbitrary‐Lagrangian‐Eulerian‐(ALE)‐Algorithmus mit der Grundwasserströmungsgleichung. Die Simulationsergebnisse werden mit mehreren analytischen Lösungen verglichen und verifiziert. Das entwickelte numerische Modell berücksichtigt auch Vertikalströmungen und eignet sich somit zur Simulation der Grundwasserströmung in der Nähe von VCW. Folglich kann nun die Lage des Grundwasserspiegels, vor allem für ungespannte Grundwasserleiter, präzise berechnet werden. Nach erfolgter Kalibrierung des numerischen Modells anhand von Felddaten wurde eine Sensitivitätsanalyse relevanter Parameter im Hinblick auf die erzielte Absenkung und deren Auswirkungen auf die Grundwasserströmungssituation durchgeführt. Die dabei erhaltenen Ergebnisse zeigen, dass die Grundwasserabsenkung proportional zur Pumprate, indirekt proportional zur hydraulischen Leitfähigkeit und fast unabhängig von der Anisotropie des Grundwasserleiters um den VCW ist. Des Weiteren zeigte sich, dass die Lage des oberen Entnahmepunktes einen größeren Einfluss auf die Absenkung als die Lage des darunter liegenden Injektionspunktes hat. Die Größe des von der Grundwasserzirkulation beeinflussten Bereiches hängt dagegen neben dem Abstand dieser beiden Punkte hauptsächlich auch von der Anisotropie des Aquifermaterials ab. Um den Einfluss der Hydrostratigraphie auf die Grundwasserströmung zu untersuchen, wurden die Eigenschaften der einzelnen Schichten genau charakterisiert. Hierfür wurden Direct‐Push‐, Pump‐, Injektions‐ sowie Zirkulationsversuche an einem Feldstandort durchgeführt. Zudem wurden Bohrkerne entnommen und mithilfe von Siebanalysen vertikale Korngrößenverteilungsprofile im Labor bestimmt. Die eingesetzten experimentellen Methoden stellen in Kombination mit numerischen Simulationsrechnungen eine gute Basis dar, um die Rolle der Schichtstruktur im Aquifer besser beurteilen zu können. Die Untersuchungen leisten somit einen wichtigen Beitrag für das zukünftige Design und den Betrieb von VCW für Grundwasserabsenkungszwecke in ungespannten Grundwasserleitern. Zudem zeigt die hier vorliegende Arbeit das große Potential dieser neuen Grundwasserabsenkungstechnik als vielversprechende Alternative zu konventionellen Absenkungsverfahren auf.

Dans l’industrie pharmaceutique, la granulation sèche par compactage à rouleaux est un procédé d’agglomération de poudres en granulés pour améliorer les propriétés d’écoulement nécessaire pour le procédé de compression en matrice. Comprendre le procédé de compactage à rouleaux et optimiser l’efficacité de production est limitée par l’utilisation de l’approche expérimentale à cause du coût élevé des poudres, le temps des essais et la complexité du procédé. Dans ce travail, une méthode d’éléments finis en 3D, est développée dans le but d’identifier les paramètres critiques du matériau et du procédé pour le contrôle de la qualité de la production. Le modèle de comportement de Drucker-Prager Cap est utilisé pour décrire le comportement en compression de poudres et sa calibration est déterminée à partir des essais standard. Pour surmonter la complexité liée à l’existence de deux mécanismes différents, l’alimentation en poudre par une vis sans fin et le compactage entre les rouleaux, une nouvelle méthode d’interfaçage entre la méthode des éléments discrets (DEM) employée pour décrire l’écoulement dans l’alimentation et la méthode des éléments finis (FEM) utilisée pour le compactage entre les rouleaux est développée. Enfin, pour une modélisation de compactage de rouleaux plus réaliste, prenant en compte la variation de l’entrefer entre les rouleaux, une nouvelle approche de couplage Euler-Lagrange est proposée. Les résultats de simulations par éléments finis montrent clairement l’effet des différents paramètres du procédé sur les distributions de pression et de densité dans la zone de compactage. En outre, les résultats montrent que l'utilisation de plaques de confinement de la poudre entre les rouleaux, développe une distribution de pression et de densité non homogène dans le compact, avec une densité plus élevée au centre et plus faible aux bords. D'autre part, l’utilisation de rouleaux dont l’un est surmonté d’une jante de confinement, a montré une distribution de propriétés globalement plus uniforme sur la largeur du compact avec des valeurs légèrement plus élevées aux bords qu’au centre. La méthodologie combinant les méthodes DEM & FEM montre clairement une corrélation directe entre la vitesse des particules entraînées par la vis dans la zone d’alimentation et la pression du rouleau. Tous les deux oscillent avec la même période. Cela se traduit par un compact anisotrope avec un profile de densité variant de manière sinusoïdale le long de sa largeur. Afin d'étudier la capacité du modèle à prédire les propriétés des compacts produits par compactage à rouleaux, les prédictions par simulations numériques sont comparées aux données de la littérature et validées par des mesures spécifiques. / In the pharmaceutical industry, dry granulation by roll compaction is a process of size enlargement of powder into granules with good flowability for subsequent die compaction process. Understanding the roll compaction process and optimizing manufacturing efficiency is limited using the experimental approach due to the high cost of powder, time-consuming and the complexity of the process. In this work, a 3D Finite Element Method (FEM) model was developed to identify the critical material properties, roll press designs and process parameters controlling the quality of the product. The Drucker-Prager Cap (DPC) model was used to describe the powder compaction behavior and was determined based on standard calibration method. To overcome the complexity involving two different mechanisms of powder feeding by the screw and powder compaction between rolls, a novel combined approach of Discrete Element Method (DEM), used to predict the granular material flow in the feed zone and the Finite Elements Method (FEM) employed for roll compaction, was developed. Lastly, for a more realistic roll compaction modelling, allowing the fluctuation of the gap between rolls, a Coupled-Eulerian Lagrangian (CEL) approach was developed. FEM simulation results clearly show the effect of different process parameters on roll pressure and density distribution in the compaction zone of powder between the rolls. Moreover, results show that using a cheek-plates sealing system causes a nonuniform roll pressure and density distribution with the highest values in the middle and the lowest at the edges. On the other hand, the resultant pressure and density distributions with the rimmed-roll obtained higher values in the edges than in the middle and overall a more uniform distribution. The combined DEM-FEM methodology clearly shows a direct correlation between the particle velocity driven by the screw conveyor to the feed zone and the roll pressure, both oscillating in the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its length. To validate the results, the simulations are compared with literature and experimentally measured values in order to assess the ability of the model to predict the properties of the produced ribbons.