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Yes / For the first time, a set of Lattice-Boltzmann two-way coupling pointwise Euler-Lagrange models is applied to gas mixing of sludge for anaerobic digestion. The set comprises a local model, a “first-neighbour” (viz., back-coupling occurs to the voxel where a particle sits, plus its first neighbours) and a “smoothing-kernel” (forward- and back-coupling occur through a smoothed-kernel averaging procedure). Laboratory-scale tests display grid-independence problems due to bubble diameter being larger than voxel size, thereby breaking the pointwise Euler-Lagrange assumption of negligible particle size. To tackle this problem and thereby have grid-independent results, a novel data-scaling approach to pointwise Euler-Lagrange grid independence evaluation, based on an application of the Buckingham π theorem, is proposed. Evaluation of laboratory-scale flow patterns and comparison to experimental data show only marginal differences in between the models, and between numerical modelling and experimental data. Pilot-scale simulations show that all the models produce grid-independent, coherent data if the Euler-Lagrange assumption of negligible (or at least, small) particle size is recovered. In both cases, a second-order convergence was achieved. A discussion follows on the opportunity of applying the proposed data-scaling approach rather than the smoothing-kernel model.

La thèse porte sur l'étude de la réduction de traînée par injection de bulles. La réduction de traînée présente un intérêt pour les applications navales puisqu'elle est issue d'une modification des structures cohérentes qui contribuent le plus à la résistance à l'avancement. Le but de cette étude est d'analyser les mécanismes à l'origine de cette diminution du frottement pariétal. L'approche utilisée dans le cadre de cette étude est numérique, elle emploie le code JADIM par une approche Euler-Lagrange : la phase continue est simulée par Simulation Numérique Directe et la phase dispersée est simulée en suivant individuellement chaque bulle. La configuration retenue dans le cadre de cette étude est celle de l'écoulement de Taylor-Couette (écoulement compris entre deux cylindres en rotation). La première partie de la thèse vise à adapter l'outil numérique employé, afin de pouvoir prendre en compte le retour de la phase dispersée via des termes de forçage dans les équations bilan de matière et de quantité de mouvement. La deuxième partie de la thèse vise à étudier l'écoulement porteur en configuration monophasique, afin de disposer d'une référence sur l'écoulement non perturbé. La troisième partie de la thèse a pour objectif d'étudier la dispersion passive des bulles dans le système, afin d'analyser les mécanismes de migrations mis en jeu. Enfin la dernière partie de la thèse vise à étudier l'influence des bulles sur l'écoulement porteur en analysant l'effet de certains paramètres, notamment le taux de vide et la flottabilité. / The study deals with drag reduction induced by bubble injection, its application concerns naval transport. The aim of the study is to shed more light on mechanisms that are involved in this wall friction reduction. The study is based on a numerical approach, and use the JADIM code with an Euler-Lagrange approach: the continuous phase is solved by Direct Numerical Simulation, and the disperse phase by a tracking of each bubble. Within the framework of this study we consider the Taylor-Couette flow configuration (flow between two concentric cylinders in rotation). The first part of the study deals with the modification of the numerical tool, in order to take into account the influence of the disperse phase on the continuous one through forcing terms in the mass and momentum balance equations. The aim of the second part is to study de Taylor-Couette flow in its monophasic configuration, for the purpose of providing a reference of the undisturbed flow. The third part deals with the passive dispersion of bubble in Taylor-Couette flow, in order to analyze the migration mechanisms involved. And the aim of the last part is to study the effects of the disperse phase on the continuous one, by analyzing the influence of bubbly phase parameters (like void fraction and buoyancy).

[pt] Essa tese considera um modelo não linear para se obter previsões de curto prazo de carga de energia elétrica. O modelo combina um modelo de múltiplos regimes auto-regressivo com transição suave com um periódico auto-regressivo criando o modelo de múltiplos regimes periódico com transição suave (STPAR). Um método de construção do modelo é desenvolvido com métodos estatísticos simples e um teste de linearidade contra a hipótese de modelo periódico autoregressivo com transição suave. Outros dois destes foram elaborados para se avaliar o modelo estimado: um teste de Multiplicador de Lagrange (LM) para a hipótese de auto-correlação serial dos resíduos e outro teste LM para a hipótese de não linearidade remanescente. Um experimento de Monte Carlo foi implementado para avaliar a performance dos testes propostos. Estimação por mínimos quadrados não lineares é considerado. Finalmente, dados de carga de energia elétrica do estado de New South Wales na Austrália são apresentados e foram usados como exemplo real. Outros modelos foram utilizados para comparar a performance do modelo. / [en] This thesis considers a non linear approach to obtain short term forecast for electricity load. The model combines a smooth transition autoregressive process with a periodic autoregressive time series model, creating the Smooth Transition Periodic Autoregressive (STPAR) model. A model-building procedure is developed and a linearity test against smooth transition periodic auto-regressive is proposed. Other two tests were created to evaluate the model: a Lagrange multiplier (LM) test for the hypothesis of no error autocorrelation and LM-type test for the hypothesis of no remaining non-linearity. A Monte Carlo experiment was implemented to evaluate the performance of the proposed tests. Estimation by nonlinear least squares is considered. Finally, load data from New South Wales State in Australia`s electricity retail market is presented and will be used as a real example. Other models were used to compare the performance of the proposes model.

Apresentaremos uma classe de energias potenciais $\\Pi \\in C^{\\infty}(\\Omega,R)$ que são s-decidíveis e que admitem funções auxiliares de Cetaev da forma $\\langle abla j^s\\Pi(q),q angle$, $q\\in \\Omega \\subset R^n$ que são s-resistentes. / We will present a class of potential energies $\\Pi \\in C^{\\infty}(\\Omega,R)$ that are s-decidable and that admit auxiliary functions of Cetaev of the form $\\langle abla j^s\\Pi(q),q angle$, $q \\in \\Omega \\subset R^n$ which are s-resistant.

[pt] Neste trabalho apresenta-se uma metodologia pelo método dos elementos finitos para a análise estática-dinâmica bi-dimensional de linhas marítimas considerando-se o contato com o leito marinho. Para o cabo considera-se o elemento de dois nós do modelo de viga de Euler-Bernoulli com as grandezas estáticas e dinâmicas referidas a um sistema co- rotacionado. Considera-se a nãolinearidade geométrica associada ao movimento de corpo rígido da estrutura, supondo pequenas deformações. No movimento da linha, são consideradas as influências do peso próprio, empuxo, carregamentos hidrodinâmicos das correntes marinhas, deslocamentos prescritos no ponto superior da linha, forças de inercia e ação de flutuadores. Os efeitos sobre a linha associados ao contato com o fundo marinho são considerados empregando-se a técnica dos multiplicadores de Lagrange. Estes representam o carregamento (forças e momentos) requerido para garantir as restrições geométricas. No modelo não são considerados os efeitos das forças de atrito com o fundo marinho, cuja rigidez é considerada muito superior à do cabo. A matriz de rigidez usual do modelo de vigas é aumentada de forma a acomodar as novas incógnitas resultantes da imposição das condições de contato. Desta forma, condições de contato, separação repetidos (contato variável) e grandes movimentos relativos do cabo com o leito são contemplados pelo modelo. A solução das equações algébricas não-lineares, resultantes da integração temporal passo-a-passo de Newmark, é obtida com a técnica iterativa de Newton Raphson. A metodologia numérica foi implementada e resultados de alguns testes para situações da engenharia offshore são mostrados e comparados com os apresentados por outros autores independentes. / [en] In this work a finite element methodology for two- dimensional static and/or dynamic analysis of maritime risers including contact with the seabed is considered. The line is modeled by a two node beam element based on the Euler- Bernoulli theory with a co-rotational coordinate system, defined from the structure space coordinate nodes, to refer the element equilibrium and motion equations. Geometric non-linear effects are considered, all associated with rigid body motions from the structure, under small strain hypothesis. In the riser motion, the influences of its own weight, buoyancy forces, hydrodynamic loadings due to the maritime currents, the prescribed displacements at the top point line, the inertia forces and the floating action are considered. Effects on the line associated to the seabed contact are considered using Lagrange multipliers. They represent, the required loading (forces and moments) to ensure the cable geometric restrictions. In the model, friction forces effects on the seabed are not considered and the seabed stiffness is taken much greater than the riser s. The beam model stiffness matrix results into an increased matrix to accommodate the new model unknowns reactions, which are represented by the contact forces and moments. Similarly, conditions for variable contact and/or separation, as well as large relative motions between the flexible line and the seabed, are contemplated by the model. Solutions of the resulting nonlinear motion equations are obtained using Newmark s step-by-step time integration procedure with the Newton-Raphson iterative technique, for the numerical solution convergence. The methodology has been implemented and some representative offshore engineering testing analysis results are presented compared to other independently published solutions.

Es werden Kontaktprobleme im Rahmen der nichtlinearen Elastizitätstheorie mit Mitteln der Variationsrechnung behandelt. Dabei liegt das Hauptaugenmerk auf der Untersuchung des Selbstkontakts eines nichtlinear elastischen Körpers. Unter Verwendung einer geeigneten Lagrangeschen Multiplikatorenregel wird eine notwendige Bedingung für Minimierer hergeleitet. Weiterhin werden Ergebnisse für den Kontakt zweier elastischer Körper formuliert.

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Submitted by Raniere Barreto (raniere.barros@ufvjm.edu.br) on 2018-04-11T18:25:08Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) bruce_franca_guimaraes.pdf: 1772676 bytes, checksum: 70105fe5762f394af52a5b015acc42e3 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2018-04-20T13:42:12Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) bruce_franca_guimaraes.pdf: 1772676 bytes, checksum: 70105fe5762f394af52a5b015acc42e3 (MD5) / Made available in DSpace on 2018-04-20T13:42:12Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) bruce_franca_guimaraes.pdf: 1772676 bytes, checksum: 70105fe5762f394af52a5b015acc42e3 (MD5) Previous issue date: 2017 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O foco do presente trabalho ? apresentar um estudo sobre fun??es reais de v?rias vari?veis reais, bem como, estudar as principais t?cnicas envolvendo esse tipo de fun??o. Conv?m destacar os conceitos de limites, derivadas parciais, m?ximos e m?nimos multiplicadores de Lagrange. Na parte final da disserta??o, apresentamos uma aplica??o na Engenharia. / Disserta??o (Mestrado Profissional) ? Programa de P?s-Gradua??o Matem?tica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / The focus of the present work is to present a study on the real functions of several real variables, as well as to study the main techniques involving this type of function. It is worth mentioning the concepts of limits, partial derivatives, maximum and minimum and Lagrange multipliers. In the final part of the dissertation, we present an application in Engineering.