Tesis sobre el tema "Maillage à pas variable"
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Tissafi, Bouchra. "Résolution couplée des équations de l'électromagnétisme et du transport en 3D pour des applications THz : modélisation et optimisation du photo-commutateur". Paris 11, 2010. http://www.theses.fr/2010PA112313.
Texto completoThis thesis investigates the three-dimensional modelling of Maxwell equations coupled with Boltzmann equation in THz devices. This work is part of the search for new optoelectronic devices operating at THz frequency. The modelled device in this thesis is a metal-semiconductor-metal photoconductive switch (PCS) fabricated on InP which is fully compatible with the technology of telecom circuits. This thesis deals with three important topics: 1/ The dévelopment of IEF-made code "Maxtra3D" that coupled equations of electromagnetism and Transport (model drift-diffusion and hydrodynamic model). Thus, to confirm the relevance of our modelling choices, we compare our software based on the FDTD method with variable mesh with two other software: IRCOM software that is based on FDTD method with constant mesh and LGEP software based on finite element method. 2/ Evaluation of loss origins in the coplanar waveguide that provides the environment for the generation and propagation of the THz wave. 3 / Parametric study and optimization of PCS. Other PCS geometries were modelled as part of this optimization
Bals, Gilbert. "Analyse experimentale et theorique du fonctionnement d'une eolienne a pas variable". Poitiers, 1987. http://www.theses.fr/1987POIT2118.
Texto completoBals, Gilbert. "Analyse expérimentale et théorique du fonctionnement d'une éolienne à pas variable". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37602564g.
Texto completoSofiane, Yamina. "Contribution à l'étude et à la modélisation d'un moteur à reluctance variable à double saillance de type pas-à-pas". Lille 1, 2001. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2001/50376-2001-313.pdf.
Texto completoCe modèle étant basé sur des hypothèses simplificatrices, l'amélioration de la précision nécessite l'utilisation d'approches numériques. Le modèle bidimensionnel, basé sur la méthode des éléments finis (MEF-2D), est alors appliqué à l'étude de notre structure avec et sans couplage circuit. Le convertisseur statique, ainsi que la commande, sont également pris en compte pour l'étude du système complet. D'autre part, un modèle analytique non linéaire, utilisant la notion d'inductance saturée, est introduit pour effectuer la même étude. Les résultats, obtenus par les deux approches, sont comparés. Pour tenir compte des effets d'extrémités, une modélisation 3D a été effectuée en magnétostatique. Les inductances, qui prennent, d'une manière globale, les effets des têtes de bobines, sont alors approximées et introduites dans le modèle 2D. Ce dernier modèle est ensuite utilisé pour étudier le dispositif. Les résultats, issus des trois modèles sont comparés à des essais expérimentaux réalisés sur un prototype de MRV à l'université de Dresde en Allemagne. Enfin, dans le but d'améliorer la précision, nous avons utilisé une méthode analytique, couplée à chacun des trois modèles proposés, pour quantifier les pertes fer de la structure pour différents régimes de fonctionnement
NGUYEN, QUANG HAN. "Controle actif du bruit en conduit developpement et implantation d'un algorithme a pas variable". Toulouse 3, 1999. http://www.theses.fr/1999TOU30077.
Texto completoDuval, Simon. "Lasers à fibre femtoseconde utilisant une paire de réseaux de Bragg à pas variable". Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/25831.
Texto completoIn this master’s thesis, we present a new type of femtosecond fiber ring laser that uses a pair of chirped fiber Bragg gratings with opposite dispersion. The presence of such elements in a ring cavity reveals a new mode locking regime where a femtosecond pulse evolving in one section of the cavity is locally transformed into a highly chirped picosecond pulse that propagates in the remaining part of the cavity. The section in which the highly chirped pulse propagates acts essentially as an all-fiber linear dispersive delay line. This portion can thus be modified in order to change the net cavity dispersion or the repetition rate of the laser without significantly increasing the nonlinear effects in the cavity. This erbium-doped fiber laser that generates sub-100 fs pulses in any dispersion regime can potentially produce highenergy ultrashort pulses (> 20 nJ; < 50 fs). This source appears to be a practical all-fiber alternative to femtosecond solid-state lasers.
Lachaud, Jacques-Olivier. "Extraction de surfaces à partir d'images tridimensionnelles : approche discrète et approche par modèle déformable". Phd thesis, Université Joseph Fourier (Grenoble), 1998. http://tel.archives-ouvertes.fr/tel-00004892.
Texto completoRodríguez, Jerónimo. "Raffinement de Maillage Spatio-Temporel pour les Équations de l'Élastodynamique". Phd thesis, Université Paris Dauphine - Paris IX, 2004. http://tel.archives-ouvertes.fr/tel-00012034.
Texto completoOlivier, Géraldine. "Adaptation de maillage anisotrope par prescription de champ de métriques appliquée aux simulations instationnaires en géométrie mobile". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00739406.
Texto completoDelisle, Simard Alexandre. "Étude de sauts de phase distribués sur un réseau de Bragg à pas linéairement variable". Thesis, Université Laval, 2009. http://www.theses.ulaval.ca/2009/26524/26524.pdf.
Texto completoSimard, Alexandre D. "Étude de sauts de phase distribués sur un réseau de Bragg à pas linéairement variable". Master's thesis, Université Laval, 2009. http://hdl.handle.net/20.500.11794/21112.
Texto completoGauci, Éléonore. "Adaptation de maillage orientée fonctionnelle et basée sur une métrique pour des simulations aérodynamiques en géométrie variable". Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4227/document.
Texto completoWhen dealing with CFD problems, mesh adaptation is interesting for its ability to approach the asymptotic convergence and to obtain an accurate prediction for complex flows at a lower cost. Anisotropic mesh adaptation method reduces the number of degrees of freedom required to reach a given solution accuracy, thus impact favorably the CPU time. Moreover, it reduces the numerical scheme dissipation by automatically taking into account the anisotropy of the physical phenomena inside the mesh. Two main approaches exist in the literature. Feature-based mesh adaptation which is mainly deduced from an interpolation error estimate using the Hessian of the chosen sensor controls the interpolation error of the sensor over the whole computational domain. Such approach is easy to set-up and has a wide range of application, but it does not take into account the considered PDE used to solve the problem. On the other hand, goal-oriented mesh adaptation, which focuses on a scalar output function, takes into consideration both the solution and the PDE in the error estimation thanks to the adjoint state. But, the design of such error estimate is much more complicated. This thesis presents the results obtained with different CFD methods : the Arbitrary Lagrangian Eulerian (ALE) flow solvers with explicit and implicit schemes are presented and coupled to the moving mesh process, the feature-based unsteady mesh adaptation for moving geometries takes into account the changes of connectivites during the whole simulation, the adjoint state is extended to moving geometries problems and goal-oriented unsteady mesh adaptation for moving meshes is derived from an a priori error estimate. Several numerical examples are considered in the aeronautics sector and the field of civil security
Chen, Fengwei. "Contributions à l'identification de modèles à temps continu à partir de données échantillonnées à pas variable". Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0149/document.
Texto completoThe output of a system is always corrupted by additive noise, therefore it is more practical to develop estimation algorithms that are capable of handling noisy data. The effect of white additive noise has been widely studied, while a colored additive noise attracts less attention, especially for a continuous-time (CT) noise. Sampling issues of CT stochastic processes are reviewed in this thesis, several sampling schemes are presented. Estimation of a CT stochastic process is studied. An expectation-maximization-based (EM) method to CT autoregressive/autoregressive moving average model is developed, which gives accurate estimation over a large range of sampling interval. Estimation of CT Box-Jenkins models is also considered in this thesis, in which the noise part is modeled to improve the performance of plant model estimation. The proposed method for CT Box-Jenkins model identification is in a two-step and iterative framework. Two-step means the plant and noise models are estimated in a separate and alternate way, where in estimating each of them, the other is assumed to be fixed. More specifically, the plant is estimated by refined instrumental variable (RIV) method while the noise is estimated by EM algorithm. Iterative means that the proposed method repeats the estimation procedure several times until a optimal estimate is found. Many practical systems have inherent time-delay. The problem of identifying delayed systems are of great importance for analysis, prediction or control design. The presence of a unknown time-delay greatly complicates the parameter estimation problem, essentially because the model are not linear with respect to the time-delay. An approach to continuous-time model identification of time-delay systems, combining a numerical search algorithm for the delay with the RIV method for the dynamic has been developed in this thesis. In the proposed algorithm, the system parameters and time-delay are estimated reciprocally in a bootstrap manner. The time-delay is estimated by an adaptive gradient-based method, whereas the system parameters are estimated by the RIV method. Since numerical method is used in this algorithm, the bootstrap method is likely to converge to local optima, therefore a low-pass filter has been used to enlarge the convergence region for the time-delay. The performance of the proposed algorithms are evaluated by numerical examples
Ben, Saad Kamel. "Modélisation et commande d'un moteur pas à pas tubulaire à reluctance variable et à quatre phases : approches conventionnelles par logique floue et par réseaux de neurones artificiels". Ecole Centrale de Lille, 2005. http://www.theses.fr/2005ECLI0001.
Texto completoNguyen, Quang Long. "Adaptation dynamique de maillage pour les écoulements diphasiques en conduites pétrolières : Application à la simulation des phénomènes de terrain slugging et severe slugging". Paris 6, 2009. https://tel.archives-ouvertes.fr/tel-01583888.
Texto completoWu, Xunqi. "Etude de cavités optiques formées de miroirs de Bragg à réseaux à pas variable : application aux filtres et lasers". Phd thesis, Supélec, 2012. http://tel.archives-ouvertes.fr/tel-00817846.
Texto completoBozorgui, Shirin. "Modelisation des lasers semiconducteurs a reflecteur de bragg (dbr) : analyse des effets thermiques et du reseau a pas variable". Paris 11, 1997. http://www.theses.fr/1997PA112316.
Texto completoElmo, Marc. "Etude du mélange en turbulence isotrope par fonctions densité de probabilité et interprétation géométrique". Ecully, Ecole centrale de Lyon, 2000. http://www.theses.fr/2000ECDL0024.
Texto completoUnderstanding of turbulent mixing is of large interest for the description of many practical problems such as dispersion of a passive scalar or turbulent reactive flows. The probabilistic description of a scalar mixed in a turbulent flow is well suited to account for a chemical reaction. Indeed the probability density function (p. D. F. ) approach allows to account for a chemical reaction term in a closed form. Unfortunately the equation governing the p. D. F. Remains unclosed since the effect of turbulent mixing appears through the conditional scalar dissipation which is unknown and needs to be modelled. The aim of this study is to investigate the behavior of a passive scalar in isotropic turbulence. Direct Numerical Simulations (D. N. S. ) and Large Eddy Simulations (L. E. S. ) are performed. A new technique of injection of scalar fluctuations is developed. This method of injection allows to obtain statistically stationary states associated with different levels of mixing. Moreover this technique gives the control of the integral scalar length scale. The situations of mixing obtained with this forcing technique are essentially analyzed in terms of p. D. F. And conditional scalar dissipation which are the key quantifies of this study. Analysis of the spectra indicates the role played by the different scales involved in the mixing process. A geometrical interpretation of the mechanisms of mixing is proposed by an investigation of the behavior of iso-scalar surfaces. The influence of the rate of injection and of the ratio of the integral length scale of the scalar and of the integral length scale of the velocity is studied. Some conclusions have also been reached about the influence of the Reynolds number and of the Schmidt number. The last part of the study is devoted to the subgrid modeling. The issue of the contribution of the small scales to the statistics of the scalar has been investigated
Sirbu, Marina. "Couplage des équations de Maxwell avec l'équation de Boltzmann en 3D : appliqué à la modélisation d'un photocommutateur THz". Paris 11, 2005. http://www.theses.fr/2005PA112255.
Texto completoThis PhD thesis presents the coupling between the Boltzmann transport equations and the electromagnetic field equations in a photoconductive switch generating THz signals. First, the transport equations are solved in the drift diffusion approximation. Then, a more complex resolution is made with a Monte Carlo based model. The photoconductive switch is located is coplanar wave guide whose dimensions are comparables with the existents structures. The numerical constraints come from the time dependant resolution, the necessarily space mesh, the simulation domain dimensions, boundary conditions and non linearity introduced by the time and space coefficients variation. The 3D equation system is solved with the variable space step FDTD (Finite Difference Time Domain) method, which allows a sufficiently refined mesh inside the switch. We have studied the photoconductive switch response when a femto second optic excitation is applied. We have shown the electromagnetic field implication in the device response origin. We also made a parametric analysis identifying the main parameters controlling the electromagnetic THz pulse. There is a good agreement between the modelling results and the experimental data. The Monte Carlo method allows taking into account the inertial effects between the electromagnetic field variation and the carrier response. This method is still in developing phase, but we have obtained good preliminary results
Rabih, Amine. "Calcul et optimisation des machines hybrides à double excitation axiale : dimensionnement et choix des aimants permanents". Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPL013N.
Texto completoLe, Thi Huyen Cham. "Robust variable kinematics plate finite elements for composite structures". Thesis, Paris 10, 2019. http://faraway.parisnanterre.fr/login?url=http://bdr.parisnanterre.fr/theses/intranet/2019/2019PA100053/2019PA100053.pdf.
Texto completoThe aim of this work is the development of two classes of new four-node and eightnode quadrilateral finite elements implemented into the commercial finite element (FE) code Abaqus for composite plates. Variable kinematics plate models are formulated in the framework of Carrera’s Unified Formulation (CUF), which encompasses Equivalent Single Layer (ESL) as well as Layer-Wise (LW) models, with the variables that are defined by polynomials up to 4th order along the thickness direction z. The two classes refer to two variational formulations that are employed to derive the finite elements matrices, namely the Principle of Virtual Displacement (PVD) and Reissner’s Mixed Variational Theorem (RMVT). Thanks to the static condensation technique, a Hybrid formulation based on the RMVT is derived. For the purpose of eliminating the shear locking pathology, two field compatible approximations for only the z−constant transverse shear strain terms, referred to as QC4 and CL8 interpolations, are extended to all variable kinematics CUF plate elements. Moreover, the QC4S and CL8S interpolations, are also introduced for the transverse shear stress field within RMVT-based and Hybrid mixed-based elements. Numerical results in comparison with those available in literature show that the proposed FEs are efficient for modeling a robust finite elements
Crétois, Emmanuelle. "Utilisation de la méthode des pas aléatoires en estimation dans les processus ponctuels". Rouen, 1994. http://www.theses.fr/1994ROUE5022.
Texto completoLaux, Sébastien. "Vers l'élaboration d'un matériau holographique de dimension centimétrique pour l'enregistrement de réseaux de phase en volume à pas variable (réseaux de Bragg chirpés) : Application à l'étirement d'impulsions laser ultra-courtes". Phd thesis, Ecole Polytechnique X, 2010. http://pastel.archives-ouvertes.fr/pastel-00503043.
Texto completoChalayer, Rénald. "Méthodes de projection pour des écoulements à seuil, incompressibles et à densité variable". Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC089.
Texto completoThis thesis deal with the use of projection methods for incompressible viscoplastic flows with a variable density. This manuscript is organized following three main lines. The first part is devoted to the mathematical model, the time-discretization of the model and the analysis of the numerical scheme. To construct the numerical scheme, on one side we adapt a time-stepping method already used for newtonian flows to viscoplastic flows and on the other side, we use a projection formulation of the stress tensor to solve the coupling between the velocity and the plastic part of the stress tensor in the momentum equation with an Uzawa-like method. Stability and error analysis of the numerical scheme are provided and a first-order estimate of the time error is derived for the velocity field, the density, the viscosity and the yield stress. The second part is devoted to the space discretization and the implementation of the scheme. A second-order cell-centred finite volume scheme on staggered grids is applied for the spatial discretization. The implementation of the numerical scheme has been performed using a Fortran 90 code and using the PetsC and MPI library The last part of the manuscript is devoted to numerical simulations. In the Rayleigh-Taylor instability configuration, we perform simulations by varying the yield stress, and describing the evolution of the interface and the localization of the rigid zones. In the dambreak configuration, we use Stick-Slip boundary conditions and we compare our results to the existing literature
Thévenot, Vincent. "Contribution à la maîtrise des phénomènes vibratoires en usinage de parois minces : Application à l'usinage de pales aéronautiques". Phd thesis, Toulouse, INPT, 2005. http://oatao.univ-toulouse.fr/7081/1/thevenot1.pdf.
Texto completoThévenot, Vincent. "Contribution à la maîtrise des phénomènes vibratoires en usinage de parois minces : application à l'usinage de pales aéronautiques". Phd thesis, Toulouse, INPT, 2005. https://hal.science/tel-04417279v1.
Texto completoThe evolution of machines, cutting tools and CAM softwares permitted to increase the performances of machining process. The use of high spindle speed leads to vibratory problems of cutting which damage the surface quality. The stability lobes theory permits to determine cutting conditions which guarantee a high chip flow without vibrations. This theory is applied to machining of thin walled structure. We show that the dynamic characteristics of the workpiece depend on the tool position. The passage of the tool on the node and the antinode, the material removal, and the contact between the tool and the workpiece are responsible of these variations. We introduce a third dimension in the stability lobes, the position of the tool. These different approaches are experimentaly validated on test workpieces
Dad, Cherifa. "Méthodologie et algorithmes pour la distribution large échelle de co-simulations de systèmes complexes : application aux réseaux électriques intelligents (Smart Grids)". Electronic Thesis or Diss., CentraleSupélec, 2018. http://www.theses.fr/2018CSUP0004.
Texto completoThe emergence of Smart Grids is causing profound changes in the electricity distribution business. Indeed, these networks are seeing new uses (electric vehicles, air conditioning) and new decentralized producers (photovoltaic, wind), which make it more difficult to ensure a balance between electricity supply and demand, and imposes to introduce a form of distributed intelligence between their different components. Considering its complexity and the extent of its implementation, it is necessary to co-simulate it in order to validate its performances. In the RISEGrid institute, CentraleSupélec and EDF R&D have developed a co-simulation platform based on the FMI2 (Functional Mock-up Interface) standard called DACCOSIM, permitting to design and develop Smart Grids. The key components of this platform are represented as gray boxes called FMUs (Functional Mock-up Unit). In addition, simulators of the physical systems of Smart Grids can make backtracking when an inaccuracy is suspected in FMU computations, unlike discrete simulators (control units) that often can only advance in time. In order these different simulators collaborate, we designed a hybrid solution that takes into account the constraints of all the components, and precisely identifies the types of the events that system is facing. This study has led to a FMI standard change proposal. Moreover, it is difficult to rapidly design an efficient Smart Grid simulation, especially when the problem has a national or even a regional scale.To fill this gap,we have focused on the most computationally intensive part, which is the simulation of physical devices. We have therefore proposed methodologies, approaches and algorithms to quickly and efficiently distribute these different FMUs on distributed architectures. The implementation of these algorithms has already allowed simulating large-scale business cases on a multi-core PC cluster. The integration of these methods into DACCOSIM will enable EDF engineers to design « large scale Smart Grids » which will be more resistant to breakdowns
Hamiaz, Adnane. "Étude d'une méthode volumes finis pour la résolution d'un modèle non linéaire d'un couplage Maxwell/plasma dans le domaine temporel". Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1711/.
Texto completoThis thesis presents the study of an efficient numerical method to solve the Maxwell equations coupled with a fluid plasma model. The document is split into five chapters where we introduce the formulation of the physical model, a mathematical study to demonstrate the existence and uniqueness of a solution for the problem, numerical approximations of the equations, simulations and validations on 3D and 2D examples and a prospective work on a finite volume method with adaptative mesh for the 1D case. The accent is continuously put on the choice of the most efficient numerical approximation to solve the coupled problem. In this work, we exhibit the drawbacks of the finite difference method usually employed in this context. To overcome these drawbacks, we propose a method based upon a finite volume scheme which allows the capability to use local refinements. Then, to increase the gain in time CPU and memory storage, we introduce a local time-stepping scheme
Martin, Alexis. "Conception et étude d'antennes actives optiquement transparentes : de la VHF jusqu'au millimétrique". Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S126/document.
Texto completoWithin the development of the Internet of Things (IoT) and the increase of the wireless communications, antennas are even more present on everyday life. However, antenna implementation is a real challenge, from a technological point of view (antenna integration into the devices) and from a psychological point of view (acceptability by the general public). Within this framework, the development of optically transparent antennas on new surfaces (glass windows, smartphone screens . . . ) is of great interest to improve the network coverage and to assist the general public in acceptability thanks to the low visual impact of such printed antennas. The present work deals with the design, the fabrication and the characterization of optically transparent and active antennas. The transparent and conducting material used is a micrometric mesh metal film specifically developed, associating high electrical conductivity and high optical transparency. A first optically transparent and miniature FM antenna based on a MESFET transistor with micrometric size has been designed and fabricated. Frequency agile antennas operating in X-band (~10 GHz), based on a beam-lead varactor (agility ~10%) and on a ferroelectric material agility ~2%), have been developed and characterized. An optically transparent and passive antenna has been studied in V-band (~60 GHz). At last, optics (1540 nm) / microwave (1.4 GHz) transition has been performed based on the transmission of a laser beam through the transparent antenna. For all prototypes, an optical transparency level higher than 80% coupled with a sheet resistance value lower than 0.1 ohm/sq have been used
Nadau, Lionel. "Schémas numériques instationnaires pour des écoulements multiphasiques multiconstituants dans des bassins sédimentaires". Phd thesis, Université de Pau et des Pays de l'Adour, 2003. http://tel.archives-ouvertes.fr/tel-00003624.
Texto completoLebaillif, David. "Fissuration en fatigue des structures mécano-soudées soumises à un environnement mécanique complexe". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2006. http://tel.archives-ouvertes.fr/tel-00695047.
Texto completoGauden, Damien. "Etude et réalisation de composants passifs accordables pour les systèmes de télécommunication hauts débits". Rennes 1, 2003. http://www.theses.fr/2003REN1E001.
Texto completoDudouit, Yohann. "Spatio-temporal refinement using a discontinuous Galerkin approach for elastodynamic in a high performance computing framework". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0248/document.
Texto completoThis thesis studies local mesh refinement both in time and space for the second order elastodynamic equation in a high performance computing context. The objective is to develop numerical methods to treat small heterogeneities that have global impact on wave propagation. We use an internal penalty discontinuous Galerkin finite element approach for its flexibity and parallelization capabilities. The elasto-acoustic finite element formulation we discuss is elasto-acoustic in order to handle local acoustic heterogeneities. We also propose an optimized penalty term more suited to the elastodynamic equation that results in better CFL condition. We improve a second order PML formulation with an original time discretization that results in a more stable formulation. Using the p-adaptivity and nonconforming mesh capabilities of discontinuous Galerkin methods combined with a local time stepping method, we greatly reduce the high computational cost of local refinements. These methods have been implemented in C++, using template metaprogramming, in a distributed memory (MPI) and shared memory (OpenMP) parallel code. Finally, we show the potential of our methods on validation test cases and on more realistic test cases with medium including hydrofractures
Djebarri, Sofiane. "Contribution à la modélisation et à la conception optimale de génératrices à aimants permanents pour hydroliennes". Thesis, Brest, 2015. http://www.theses.fr/2015BRES0012/document.
Texto completoThe improvements of marine current turbines drive train are key features to ensure safe operation and to make tidal energy resource cost-attractive. In this context, eliminating mechanical systems that demand high-level of maintenance can be an interesting way to improve the global behavior of tidal turbines. For that purposes, the presented studies focus on design methodologies and concepts of direct-driven generators associated with fixed-pitch turbines. The proposed designs are based on multiphysics models of the generator that are integrated in an optimization process taking into account the drive train environment. For these reasons, several models have been integrated into a global design strategy in order to find solutions that improve marine current turbines performances. This strategy is based on the use of an optimization process that combines electromagnetic model, thermal model, turbine performances model, and tidal resource velocity profile. This methodology integrates also an efficient control strategy based on a maximum power point tracking (MPPT) approach at low tidal speed and a flux-weakening power limitation control at high tidal speed. This control at high tidal velocities is in this work achieved by considering only the generator electrical control without using blade pitching systems. The obtained results highlight trends that could lead to an improvement of the design and they help designers to set relevant technological choices in order to ensure significant cost reduction and highly improve the reliability of marine current turbines
Weber, Bruno. "Optimisation de code Galerkin discontinu sur ordinateur hybride : application à la simulation numérique en électromagnétisme". Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAD046/document.
Texto completoIn this thesis, we present the evolutions made to the Discontinuous Galerkin solver Teta-CLAC – resulting from the IRMA-AxesSim collaboration – during the HOROCH project (2015-2018). This solver allows to solve the Maxwell equations in 3D and in parallel on a large amount of OpenCL accelerators. The goal of the HOROCH project was to perform large-scale simulations on a complete digital human body model. This model is composed of 24 million hexahedral cells in order to perform calculations in the frequency band of connected objects going from 1 to 3 GHz (Bluetooth). The applications are numerous: telephony and accessories, sport (connected shirts), medicine (probes: capsules, patches), etc. The changes thus made include, among others: optimization of OpenCL kernels for CPUs in order to make the best use of hybrid architectures; StarPU runtime experimentation; the design of an integration scheme using local time steps; and many optimizations allowing the solver to process simulations of several millions of cells
Vu, Do Huy Cuong. "Méthodes numériques pour les écoulements et le transport en milieu poreux". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112348/document.
Texto completoThis thesis bears on the modelling of groundwater flow and transport in porous media; we perform numerical simulations by means of finite volume methods and prove convergence results. In Chapter 1, we first apply a semi-implicit standard finite volume method and then the generalized finite volume method SUSHI for the numerical simulation of density driven flows in porous media; we solve a nonlinear convection-diffusion parabolic equation for the concentration coupled with an elliptic equation for the pressure. We apply the standard finite volume method to compute the solutions of a problem involving a rotating interface between salt and fresh water and of Henry's problem. We then apply the SUSHI scheme to the same problems as well as to a three dimensional saltpool problem. We use adaptive meshes, based upon square volume elements in space dimension two and cubic volume elements in space dimension three. In Chapter 2, we apply the generalized finite volume method SUSHI to the discretization of Richards equation, an elliptic-parabolic equation modeling groundwater flow, where the diffusion term can be anisotropic and heterogeneous. This class of locally conservative methods can be applied to a wide range of unstructured possibly non-matching polyhedral meshes in arbitrary space dimension. As is needed for Richards equation, the time discretization is fully implicit. We obtain a convergence result based upon a priori estimates and the application of the Fréchet-Kolmogorov compactness theorem. We implement the scheme and present numerical tests. In Chapter 3, we study a gradient scheme for the Signorini problem. Gradient schemes are nonconforming methods written in discrete variational formulation which are based on independent approximations of the functions and the gradients. We prove the existence and uniqueness of the discrete solution as well as its convergence to the weak solution of the Signorini problem. Finally we introduce a numerical scheme based upon the SUSHI discretization and present numerical results. In Chapter 4, we apply a semi-implicit scheme in time together with a generalized finite volume method for the numerical solution of density driven flows in porous media; it comes to solve nonlinear convection-diffusion parabolic equations for the solute and temperature transport as well as for the pressure. We compute the solutions for a specific problem which describes the advance of a warm fresh water front coupled to heat transfer in a confined aquifer which is initially charged with cold salt water. We use adaptive meshes, based upon square volume elements in space dimension two
Rodríguez, Garcia Jerónimo. "Raffinement de maillage spatio-temporel pour les équations de l'élastodynamique". Phd thesis, 2004. http://pastel.archives-ouvertes.fr/pastel-00002379.
Texto completoLaux, Sébastien. "Vers l'élaboration d'un matériau holographique de dimension centimétrique pour l'enregistrement de réseaux de phase en volume à pas variable (réseaux de Bragg chirpés) : Application à l'étirement d'impulsions laser ultra-courtes". Phd thesis, 2009. http://pastel.archives-ouvertes.fr/pastel-00005685/en/.
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