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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Discontinuous Galerkin Methods for Parabolic Partial Differential Equations with Random Input Data

Liu, Kun 16 September 2013 (has links)
This thesis discusses and develops one approach to solve parabolic partial differential equations with random input data. The stochastic problem is firstly transformed into a parametrized one by using finite dimensional noise assumption and the truncated Karhunen-Loeve expansion. The approach, Monte Carlo discontinuous Galerkin (MCDG) method, randomly generates $M$ realizations of uncertain coefficients and approximates the expected value of the solution by averaging M numerical solutions. This approach is applied to two numerical examples. The first example is a two-dimensional parabolic partial differential equation with random convection term and the second example is a benchmark problem coupling flow and transport equations. I first apply polynomial kernel principal component analysis of second order to generate M realizations of random permeability fields. They are used to obtain M realizations of random convection term computed from solving the flow equation. Using this approach, I solve the transport equation M times corresponding to M velocity realizations. The MCDG solution spreads toward the whole domain from the initial location and the contaminant does not leave the initial location completely as time elapses. The results show that MCDG solution is realistic, because it takes the uncertainty in velocity fields into consideration. Besides, in order to correct overshoot and undershoot solutions caused by the high level of oscillation in random velocity realizations, I solve the transport equation on meshes of finer resolution than of the permeability, and use a slope limiter as well as lower and upper bound constraints to address this difficulty. Finally, future work is proposed.
122

Numerical Solution of Multiscale Electromagnetic Systems

TOBON, LUIS E. January 2013 (has links)
<p>The Discontinuous Galerkin time domain (DGTD) method is promising in modeling of realistic multiscale electromagnetic systems. This method defines the basic concept for implementing the communication between multiple domains with different scales.</p><p>Constructing a DGTD system consists of several careful choices: (a) governing equations; (b) element shape and corresponding basis functions for the spatial discretization of each subdomain; (c) numerical fluxes onto interfaces to bond all subdomains together; and (d) time stepping scheme based on properties of a discretized</p><p>system. This work present the advances in each one of these steps.</p><p> </p><p>First, a unified framework based on the theory of differential forms and the finite element method is used to analyze the discretization of the Maxwell's equations. Based on this study, field intensities (<bold>E</bold> and <bold>H</bold>) are associated to 1-forms and curl-conforming basis functions; flux densities (<bold>D</bold> and <bold>B</bold>) are associated to 2-forms and divergence-conforming basis functions; and the constitutive relations are defined by Hodge operators.</p><p>A different approach is the study of numerical dispersion. Semidiscrete analysis is the traditional method, but for high order elements modal analysis is prefered. From these analyses, we conclude that a correct discretization of fields belonging to different p-form (e.g., <bold>E</bold> and <bold>B</bold>) uses basis functions with same order of interpolation; however, different order of interpolation must be used if two fields belong to the same p-form (e.g., <bold>E</bold> and <bold>H</bold>). An alternative method to evaluate numerical dispersion based on evaluation of dispersive Hodge operators is also presented. Both dispersion analyses are equivalent and reveal same fundamental results. Eigenvalues, eigenvector and transient results are studied to verify accuracy and computational costs of different schemes. </p><p>Two different approaches are used for implementing the DG Method. The first is based on <bold>E</bold> and <bold>H</bold> fields, which use curl-conforming basis functions with different order of interpolation. In this case, the Riemman solver shows the best performance to treat interfaces between subdomains. A new spectral prismatic element, useful for modeling of layer structures, is also implemented for this approach. Furthermore, a new efficient and very accurate time integration method for sequential subdomains is implemented.</p><p>The second approach for solving multidomain cases is based on <bold>E</bold> and <bold>B</bold> fields, which use curl- and divergence-conforming basis functions, respectively, with same order of interpolation. In this way, higher accuracy and lower memory consumption are obtained with respect to the first approach based on <bold>E</bold> and <bold>H</bold> fields. The centered flux is used to treat interfaces with non-conforming meshes, and both explicit Runge-Kutta method and implicit Crank-Nicholson method are implemented for time integration. </p><p>Numerical examples and realistic cases are presented to verify that the proposed methods are non-spurious and efficient DGTD schemes.</p> / Dissertation
123

Direct Numerical Simulation of Compressible and Incompressible Wall Bounded Turbulent Flows with Pressure Gradients

Wei, Liang 22 December 2009 (has links)
This thesis is focused on direct numerical simulation (DNS) of compressible and incompressible fully developed and developing turbulent flows between isothermal walls using a discontinuous Galerkin method (DGM). Three cases (Ma = 0.2, 0.7 and 1.5) of DNS of turbulent channel flows between isothermal walls with Re ~ 2800, based on bulk velocity and half channel width, have been carried out. It is found that a power law seems to scale mean streamwise velocity with Ma slightly better than the more usual log-law. Inner and outer scaling of second-order and higher-order statistics have been analyzed. The linkage between the pressure gradient and vorticity flux on the wall has been theoretically derived and confirmed and they are highly correlated very close to the wall. The correlation coefficients are influenced by Ma, and viscosity when Ma is high. The near-wall spanwise streak spacing increases with Ma. Isosurfaces of the second invariant of the velocity gradient tensor are more sparsely distributed and elongated as Ma increases. DNS of turbulent isothermal-wall bounded flow subjected to favourable and adverse pressure gradient (FPG, APG) at Ma ~ 0.2 and Reref ~ 428000, based on the inlet bulk velocity and the streamwise length of the bottom wall, is also investigated. The FPG/APG is obtained by imposing a concave/convex curvature on the top wall of a plane channel. The flows on the bottom and top walls are tripped turbulent and laminar boundary layers, respectively. It is observed that the first and second order statistics are strongly influenced by the pressure gradients. The cross-correlation coefficients of the pressure gradients and vorticity flux remain constant across the FPG/APG regions of the flat wall. High correlations between the streamwise/wallnormal pressure gradient and the spanwise vorticity are found near the separation region close to the curved top wall. The angle of inclined hairpin structure to streamwise direction of the bottom wall is smaller (flatter) in the FPG region than the APG region. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2009-12-21 13:59:53.084
124

Unstetige Galerkin-Diskretisierung niedriger Ordnung in einem atmosphärischen Multiskalenmodell / Low-order discontinuous Galerkin discretization in an atmospheric multi-scale model

Orgis, Thomas January 2013 (has links)
Die Dynamik der Atmosphäre der Erde umfasst einen Bereich von mikrophysikalischer Turbulenz über konvektive Prozesse und Wolkenbildung bis zu planetaren Wellenmustern. Für Wettervorhersage und zur Betrachtung des Klimas über Jahrzehnte und Jahrhunderte ist diese Gegenstand der Modellierung mit numerischen Verfahren. Mit voranschreitender Entwicklung der Rechentechnik sind Neuentwicklungen der dynamischen Kerne von Klimamodellen, die mit der feiner werdenden Auflösung auch entsprechende Prozesse auflösen können, notwendig. Der dynamische Kern eines Modells besteht in der Umsetzung (Diskretisierung) der grundlegenden dynamischen Gleichungen für die Entwicklung von Masse, Energie und Impuls, so dass sie mit Computern numerisch gelöst werden können. Die vorliegende Arbeit untersucht die Eignung eines unstetigen Galerkin-Verfahrens niedriger Ordnung für atmosphärische Anwendungen. Diese Eignung für Gleichungen mit Wirkungen von externen Kräften wie Erdanziehungskraft und Corioliskraft ist aus der Theorie nicht selbstverständlich. Es werden nötige Anpassungen beschrieben, die das Verfahren stabilisieren, ohne sogenannte „slope limiter” einzusetzen. Für das unmodifizierte Verfahren wird belegt, dass es nicht geeignet ist, atmosphärische Gleichgewichte stabil darzustellen. Das entwickelte stabilisierte Modell reproduziert eine Reihe von Standard-Testfällen der atmosphärischen Dynamik mit Euler- und Flachwassergleichungen in einem weiten Bereich von räumlichen und zeitlichen Skalen. Die Lösung der thermischen Windgleichung entlang der mit den Isobaren identischen charakteristischen Kurven liefert atmosphärische Gleichgewichtszustände mit durch vorgegebenem Grundstrom einstellbarer Neigung zu(barotropen und baroklinen)Instabilitäten, die für die Entwicklung von Zyklonen wesentlich sind. Im Gegensatz zu früheren Arbeiten sind diese Zustände direkt im z-System(Höhe in Metern)definiert und müssen nicht aus Druckkoordinaten übertragen werden.Mit diesen Zuständen, sowohl als Referenzzustand, von dem lediglich die Abweichungen numerisch betrachtet werden, und insbesondere auch als Startzustand, der einer kleinen Störung unterliegt, werden verschiedene Studien der Simulation von barotroper und barokliner Instabilität durchgeführt. Hervorzuheben ist dabei die durch die Formulierung von Grundströmen mit einstellbarer Baroklinität ermöglichte simulationsgestützte Studie des Grades der baroklinen Instabilität verschiedener Wellenlängen in Abhängigkeit von statischer Stabilität und vertikalem Windgradient als Entsprechung zu Stabilitätskarten aus theoretischen Betrachtungen in der Literatur. / The dynamics of the Earth’s atmosphere encompass a range from microphysical turbulence over convective processes and cloud formation up to planetary wave patterns. For weather forecasting and the investigation of climate over decades and centuries, these are subject to modelling with numerical methods. With progressing development of computer technology, re-development of the dynamical cores of climate models is in order to properly handle processes covered by the increasing resolution. The dynamical core of a model consists of the adaptation(discretization)of the basic equations for the dynamics of mass, energy and momentum for solving them numerically employing computers. The presented work investigates the applicability of a low-order Discontinuous Galerkin (DG) method for atmospheric applications. With equations that include external forces like gravitation and the Coriolis force, that is not given by theory. Necessary changes for stabilizing the method without resorting to slope limiters are presented. For the unmodified method, the basic inability to properly keep atmospheric balances is demonstrated. The developed stabilized model reproduces a set of standard test cases in a wide range of spatial and temporal scales. The solution of the termal wind equation along its characteristics curves, those being identical to the isobars, produces balanced atmospheric states with tunable (barotropic and baroclinic) instability via a prescribed zonal wind field. The constructed instability directly relates to the generation of cyclones. In contrast to earlier works, these balanced states are directly given in the z system (height in meters), without need for elaborate conversion from pressure coordinates. With these constructed states, both as reference state, the deviations from which being considered numerically, and as especially as initial condition subject to a small perturbation, several studies of barotropic and baroclinic instability are conducted via simulations. Particularily, the construction of steady states with configurable zonal flows of certain baroclinity facilitates a simulation-based study of baroclinic instability of differing wavelengths, depending on static stability and vertical wind gradient, in correspondence with stability maps from theoretical considerations in the literature.
125

Das unstetige Galerkin-Verfahren in der Nanooptik

Hille, Andreas 08 March 2013 (has links) (PDF)
Die Nanooptik beschäftigt sich mit der Wechselwirkung von Licht mit Materie, deren charakteristische Dimension im Nanometer Bereich liegt. Insbesondere wenn die Materie aus Metall besteht, zeigen sich interessante, wellenlängenabhängige Unterschiede in der Stärke der Wechselwirkung. Die Ursache dafür sind die kollektiven Moden der quasifreien Ladungsträger, die Plasmonen. Obgleich sich experimentelle Methoden in den letzten Jahren stetig verbessert haben, ist es nach wie vor nur mit erheblichem Aufwand möglich, sich Einblicke in die mikroskopischen Zusammenhänge zu verschaffen. Eine Ergänzung zu den Experimenten bieten theoretische Modelle. Auf Grund der sich mit der Zeit stetig verbesserten Leistung der Rechentechnik, kommen dabei zunehmend numerische Verfahren zum Einsatz. Eines dieser Verfahren ist das Unstetige Galerkin Verfahren, welches in dieser Arbeit auf folgende Fragestellungen der plasmonischen Nanooptik angewandt wurde: • Bei dem unstetigen Galerkin Verfahren werden die zu simulierenden Körper üblicherweise mittels Dreiecke und Tetraeder approximiert. Da die Geometrie der metallischen Systeme einen entscheidenden Einfluss auf die Wechselwirkung hat, wurde untersucht, inwieweit sich durch Einsatz von Elementen mit gekrümmten Flächen die Genauigkeit oder die Geschwindigkeit der Simulation steigern lässt. Es konnte gezeigt werden, dass runde Elemente die Genauigkeit bei gleicher Diskretisierung um bis zu zwei Größenordnungen steigern oder die Rechenzeit bei gleicher Genauigkeit auf ein Sechstel verkürzen können. • Bestrahlt man Metallnanopartikel mit intensiven Laserpulsen, so strahlen diese nicht nur bei der Frequenz des eingestrahlten Lichtes, sondern auch bei der doppelten Frequenz ab. Dieses Phänomen der Frequenzverdopplung (SHG, engl.: „Second-Harmonic-Generation“) ist unter anderem von der Form der Partikel und der Wellenlänge des Pulses abhängig. Da durchstimmbare gepulste Laser sehr teuer sind, wurde untersucht, ob sich mit Hilfe der linearen Partikelspektren Vorhersagen über die Stärke der Frequenzverdopplung machen lassen. Dabei wurde festgestellt, dass die Effizienz der Frequenzverdopplung zunimmt, wenn man die linearen Resonanzen der Partikel auf die SHG- oder Anregungswellenlänge abstimmt. Schafft man es, das plasmonische System so einzustellen, dass sowohl die Anregungswellenlänge, wie auch die SHG- Wellenlänge auf einer linearen Resonanz liegen, so kann die Effizienz der SHG weiter gesteigert werden. / Nanooptics is a discipline dealing with the interaction of light with matter where its characteristic dimensions are defined to be in the range of nanometers. In particular, if the matter consists of metal, i.e. conductive material, interesting wavelength dependent phenomena can be observed, which scale with the strength of the interaction. These phenomena are caused by the formation of collective modes between quasi-free charge carriers resulting in so called plasmons. Although improved experimental methods have evolved over the last few years, insight into the microscopic relationship between light and matter is only achievable with high effort. Supplemental information to experimental findings can be drawn from theoretical models. Due to the constantly improving computational power, numerical methods are progressively more employed. One of these methods is the discontinuous Galerkin method, which was applied to the following problems in plasmonic nanooptics: • Within the discontinuous Galerkin method the simulated objects are usually approximated by triangles or tetrahedrons. Since the geometry of conductive systems has a major impact on the interaction between light and matter, the usability of elements with curved surfaces for the discretisation of the space has been investigated with respect to accuracy and speed of the simulation. In this work, it could be shown that curved elements improve the simulations precision up to two orders of magnitude with the same amount of discretisation compared to linear elements. Related to speed, it has been found that the computational time is reduced by a factor of 6 with a comparable simulation accuracy. • By irradiating metallic nanoparticles with high power laser pulses these particles do not only emit light of the same frequency as the incident electromagnetic wave, but also with the doubled frequency (SHG, second harmonic generation). Among other things, this phenomenon of frequency doubling mainly depends on the geometry of the particle and the wavelength of the pulse. Since tunable pulsed laser sources are very expensive, it has been theoretically investigated if the strength of the frequency doubling can be deduced from the particles linear spectra. By this, it has been discovered that the efficiency of frequency doubling can be improved by adjusting the linear resonances of the particle to the SHG or excitation wavelength. The SHG efficiency can be increased even further, if the plasmonic system is tuned to a point where both the excitation and the SHG wavelength correspond to a linear resonance of the nanoparticle.
126

Wavelet-based multiscale simulation of incompressible flows / Simulation multi-échelle pour les écoulements incompressibles basée sur les ondelettes

Pinto, Brijesh 29 June 2017 (has links)
Cette thèse se concentre sur le développement d'une méthode précise et efficace pour la simulation des grandes échelles (LES) des écoulements turbulents. Une approche de la LES basée sur la méthode variationnelle multi-échelles (VMS) est considérée. La VMS applique aux équations de la dynamique des fluides une séparation d'échelles a priori sans recours à des hypothèses sur les conditions aux limites ou sur l'uniformité du maillage. Afin d'assurer effectivement une séparation d'échelles dans l'espace des nombres d'onde associé, nous choisissons d'utiliser les ondelettes de deuxième génération (SGW), une base polynomiale qui présente des propriétés de localisation spatiale-fréquence optimales. A partir de la séparation d'échelles ainsi réalisée, l'action du modèle sous-maille est limitée à un intervalle de nombres d'onde proche de la coupure spectrale. Cette approche VMS-LES basée sur les ondelettes est désignée par WAVVMS-LES. Elle est incorporée dans un solveur d'ordre élevé pour la simulation des écoulements incompressibles sur la base d'une méthode de Galerkin discontinue (DG-FEM) stabilisée pour la pression. La méthode est évaluée par réalisation de LES sur des maillages fortement sous-résolus pour le cas test du tourbillon de Taylor-Green 3D à deux nombres de Reynolds différents. / This thesis focuses on the development of an accurate and efficient method for performing Large-Eddy Simulation (LES) of turbulent flows. An LES approach based upon the Variational Multiscale (VMS) method is considered. VMS produces an a priori scale-separation of the governing equations, in a manner which makes no assumptions on the boundary conditions and mesh uniformity. In order to ensure that scale-separation in wavenumber is achieved, we have chosen to make use of the Second Generation Wavelets (SGW), a polynomial basis which exhibits optimal space-frequency localisation properties. Once scale-separation has been achieved, the action of the subgrid model is restricted to the wavenumber band closest to the cutoff. We call this approach wavelet-based VMS-LES (WAV-VMS-LES). This approach has been incorporated within the framework of a high-order incompressible flow solver based upon pressure-stabilised discontinuous Galerkin FEM (DG-FEM). The method has been assessed by performing highly under-resolved LES upon the 3D Taylor-Green Vortex test case at two different Reynolds numbers.
127

Finite element methods for threads and plates with real-time applications

Larsson, Karl January 2010 (has links)
Thin and slender structures are widely occurring both in nature and in human creations. Clever geometries of thin structures can produce strong constructions while using a minimal amount of material. Computer modeling and analysis of thin and slender structures has its own set of problems stemming from assumptions made when deriving the equations modeling their behavior from the theory of continuum mechanics. In this thesis we consider two kinds of thin elastic structures; threads and plates. Real-time simulation of threads are of interest in various types of virtual simulations such as surgery simulation for instance. In the first paper of this thesis we develop a thread model for use in interactive applications. By viewing the thread as a continuum rather than a truly one dimensional object existing in three dimensional space we derive a thread model that naturally handles both bending, torsion and inertial effects. We apply a corotational framework to simulate large deformation in real-time. On the fly adaptive resolution is used to minimize corotational artifacts. Plates are flat elastic structures only allowing deflection in the normal direction. In the second paper in this thesis we propose a family of finite elements for approximating solutions to the Kirchhoff-Love plate equation using a continuous piecewise linear deflection field. We reconstruct a discontinuous piecewise quadratic deflection field which is applied in a discontinuous Galerkin method. Given a criterion on the reconstruction operator we prove a priori estimates in energy and L2 norms. Numerical results for the method using three possible reconstructions are presented.
128

Une nouvelle formulation Galerkin discontinue pour équations de Maxwell en temps, a priori et a posteriori erreur estimation. / A new Galerkin Discontinuous Formulation for time dependent Maxwell's Equations, a priori and a posteriori Error estimate.

Riaz, Azba 04 April 2016 (has links)
Dans la première partie de cette thèse, nous avons considéré les équations de Maxwell en temps et construit une formulation discontinue de Galerkin (DG). On a montré que cette formulation est bien posée et ensuite on a établi des estimateurs a priori pour cette formulation. On a obtenu des résultats numériques pour valider les estimateurs a priori obtenus théoriquement. Dans la deuxième partie de cette thèse, des estimateurs d'erreur a posteriori de cette formulation sont établis, pour le cas semi-discret et pour le système complètement discrétisé. Dans la troisième partie de cette thèse, on considére les équations de Maxwell en régime harmonique. On a développé une formulation discontinue de Galerkin mixte. On a établi des estimations d'erreur a posteriori pour cette formulation. / In the first part of this thesis, we have considered the time-dependent Maxwell's equations in second-order form and constructed discontinuous Galerkin (DG) formulation. We have established a priori error estimates for this formulation and carried out the numerical analysis to confirm our theoretical results. In the second part of this thesis, we have established a posteriori error estimates of this formulation for both semi discrete and fully discrete case. In the third part of the thesis we have considered the time-harmonic Maxwell's equations and we have developed mixed discontinuous Galerkin formulation. We showed the well posedness of this formulation and have established a posteriori error estimates.
129

Methods for solving discontinuous-Galerkin finite element equations with application to neutron transport / Méthodes de résolution d'équations aux éléments finis Galerkin discontinus et application à la neutronique

Murphy, Steven 26 August 2015 (has links)
Cette thèse traite des méthodes d’éléments finis Galerkin discontinus d’ordre élevé pour la résolution d’équations aux dérivées partielles, avec un intérêt particulier pour l’équation de transport des neutrons. Nous nous intéressons tout d’abord à une méthode de pré-traitement de matrices creuses par blocs, qu’on retrouve dans les méthodes Galerkin discontinues, avant factorisation par un solveur multifrontal. Des expériences numériques conduites sur de grandes matrices bi- et tri-dimensionnelles montrent que cette méthode de pré-traitement permet une réduction significative du ’fill-in’, par rapport aux méthodes n’exploitant pas la structure par blocs. Ensuite, nous proposons une méthode d’éléments finis Galerkin discontinus, employant des éléments d’ordre élevé en espace comme en angle, pour résoudre l’équation de transport des neutrons. Nous considérons des solveurs parallèles basés sur les sous-espaces de Krylov à la fois pour des problèmes ’source’ et des problèmes aux valeur propre multiplicatif. Dans cet algorithme, l’erreur est décomposée par projection(s) afin d’équilibrer les contraintes numériques entre les parties spatiales et angulaires du domaine de calcul. Enfin, un algorithme HP-adaptatif est présenté ; les résultats obtenus démontrent une nette supériorité par rapport aux algorithmes h-adaptatifs, à la fois en terme de réduction de coût de calcul et d’amélioration de la précision. Les valeurs propres et effectivités sont présentées pour un panel de cas test industriels. Une estimation précise de l’erreur (avec effectivité de 1) est atteinte pour un ensemble de problèmes aux domaines inhomogènes et de formes irrégulières ainsi que des groupes d’énergie multiples. Nous montrons numériquement que l’algorithme HP-adaptatif atteint une convergence exponentielle par rapport au nombre de degrés de liberté de l’espace éléments finis. / We consider high order discontinuous-Galerkin finite element methods for partial differential equations, with a focus on the neutron transport equation. We begin by examining a method for preprocessing block-sparse matrices, of the type that arise from discontinuous-Galerkin methods, prior to factorisation by a multifrontal solver. Numerical experiments on large two and three dimensional matrices show that this pre-processing method achieves a significant reduction in fill-in, when compared to methods that fail to exploit block structures. A discontinuous-Galerkin finite element method for the neutron transport equation is derived that employs high order finite elements in both space and angle. Parallel Krylov subspace based solvers are considered for both source problems and $k_{eff}$-eigenvalue problems. An a-posteriori error estimator is derived and implemented as part of an h-adaptive mesh refinement algorithm for neutron transport $k_{eff}$-eigenvalue problems. This algorithm employs a projection-based error splitting in order to balance the computational requirements between the spatial and angular parts of the computational domain. An hp-adaptive algorithm is presented and results are collected that demonstrate greatly improved efficiency compared to the h-adaptive algorithm, both in terms of reduced computational expense and enhanced accuracy. Computed eigenvalues and effectivities are presented for a variety of challenging industrial benchmarks. Accurate error estimation (with effectivities of 1) is demonstrated for a collection of problems with inhomogeneous, irregularly shaped spatial domains as well as multiple energy groups. Numerical results are presented showing that the hp-refinement algorithm can achieve exponential convergence with respect to the number of degrees of freedom in the finite element space
130

Hybridation de méthodes numériques pour l'étude de la susceptibilité électromagnétique de circuits planaires / Hybridization of numerical methods to study electromagnetic susceptibility of planar circuits

Girard, Caroline 18 December 2014 (has links)
L'étude de la susceptibilité électromagnétique de circuits électroniques nécessite l'utilisation d'un outil de simulation rapide, précis et suffisamment flexible pour intégrer les dernières innovations technologiques. La méthode itérative basée sur le concept d'onde (notée WCIP pour Wave Concept Iterative Procedure) initialement proposée par H. Baudrand est particulièrement adaptée pour la modélisation numérique de circuits multicouches à plusieurs niveaux de métallisation. Pour ce type de circuits, elle se révèle être l'une des méthodes qui utilise le plus petit nombre d'inconnues pour atteindre une précision donnée. Néanmoins, la WCIP n'est pas adaptée à la prise en compte des diélectriques inhomogènes et des trous d'interconnexion. L'objectif de la thèse est de s'affranchir de ces limitations par un couplage avec des méthodes numériques volumiques. En premier lieu, l'hybridation a été mise en œuvre avec une méthode basée sur la théorie des lignes de transmission pour des raisons de correspondance de maillages. Par la suite, le couplage avec une technique d'éléments finis de type Galerkin Discontinu (notée GD) Hybridée permet d'atteindre des objectifs de précision et de rapidité car GD apporte une flexibilité dans la discrétisation. En effet, c'est une méthode d'éléments finis non conforme qui permet notamment de faire varier d'un élément à l'autre l'ordre polynomial d'approximation. On a ainsi développé une nouvelle méthode numérique hybride couplant la WCIP avec des méthodes volumiques qui offrent plus de souplesse pour la prise en compte des milieux complexes. Enfin, une stratégie de résolution par décomposition de domaines est également abordée à la fin du manuscrit. / Electromagnetic susceptibility study of electronic circuits requires the use of a simulation tool which is fast, accurate and flexible enough to incorporate the latest technological innovations. The Wave Concept Iterative Procedure (WCIP) initially proposed by H. Baudrand is particularly adapted for numerical modeling of multilayered circuits with multilevel metallization. For this kind of circuits, it turns out to be one of the methods that uses the smallest number of unknowns to reach a given accuracy. However, the WCIP is not appropriate for inhomogeneous dielectric substrates and metallized via holes. The aim of this PhD thesis is to overcome these limitations coupling the WCIP with volume numerical methods. First, hybridization is carried out with the Frequency Domain Transmission Line Matrix (denoted FDTLM) assuming matching meshes at the interface between computational domains of both methods. Subsequently, the coupling with a finite element technique like a Hybridized Discontinuous Galerkin (denoted DG) method is considered to achieve the objectives of accuracy and speed because DG brings flexibility in the discretization. Indeed, it is a nonconforming finite element method which allows in particular changing the polynomial approximation order from one element to another. Therefore, a new hybrid method is developed coupling the WCIP with volume numerical methods which offer more flexibility for dealing with complex environments. Finally, a domain decomposition solution strategy is also discussed at the end of the manuscript.

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