La present tesi està centrada en l'ús de la Teoria de Semblança Quàntica per a calcular descriptors moleculars. Aquests descriptors s'utilitzen com a paràmetres estructurals per a derivar correlacions entre l'estructura i la funció o activitat experimental per a un conjunt de compostos. Els estudis de Relacions Quantitatives Estructura-Activitat són d'especial interès per al disseny racional de molècules assistit per ordinador i, en particular, per al disseny de fàrmacs. Aquesta memòria consta de quatre parts diferenciades. En els dos primers blocs es revisen els fonaments de la teoria de semblança quàntica, així com l'aproximació topològica basada en la teoria de grafs. Ambdues teories es fan servir per a calcular els descriptors moleculars. En el segon bloc, s'ha de remarcar la programació i implementació de programari per a calcular els anomenats índexs topològics de semblança quàntica. La tercera secció detalla les bases de les Relacions Quantitatives Estructura-Activitat i, finalment, el darrer apartat recull els resultats d'aplicació obtinguts per a diferents sistemes biològics. / The present thesis is centred in the use of the Quantum Similarity Theory to calculate molecular descriptors. These molecular descriptors are used as structural parameters to derive correlations between the structure and the function or experimental activity for a set of compounds. Quantitative Structure-Activity Relationship studies are of special interest for the rational Computer-Aided Molecular Design and, in particular, for Computer-Aided Drug Design. The memory has been structured in four differenced parts. The two first blocks revise the foundations of quantum similarity theory, as well as the topological approximation, based in classical graph theory. These theories are used to calculate the molecular descriptors. In the second block, the programming and implementation of Topological Quantum Similarity Indices must be remarked. The third section details the basis for Quantitative Structure-Activity Relationships and, finally, the last section gathers the application results obtained for different biological systems.

Made available in DSpace on 2015-03-26T12:27:13Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3360592 bytes, checksum: 7d67d4fcf4c95ec01e67b457ff878b1e (MD5) Previous issue date: 2012-08-01 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective of the present work to start several projects with the aim of generating free systems to assist forest managers, academics and extension in solving some problems in the forest sector. The projects are started the RPF (forest regulation system), OtimTotas (optimization of multiproduct of timber system), FitFD (system for fitting of probability density functions), and Select (system for selection of data for growth and yield modeling). The projects were developed using the Java programming language. As development environment we used the IDE (Integrated Development Environment) Netbeans 7.1 and JDK 7.3 (Java Development Kit) the four systems were implemented and are freely available on the site NeuroForest (http://neuroforest.ucoz.com/) and is presented for flexible and efficient resolution of problems to which they have. / Objetivou-se no presente trabalho iniciar diversos projetos com o intuito de gerar sistemas gratuitos, para auxiliar gestores florestais, acadêmicos e extensionistas, na resolução de alguns problemas do setor florestal. Os projetos iniciados são o RPF (sistema para regulação da produção florestal), OtimTotas (sistema para otimização de multiprodutos madeireiros), FitFD (sistema para ajuste de funções densidade de probabilidade), e o Select (sistema para seleção de dados para ajuste de modelos de crescimento e produção). Os projetos foram desenvolvidos utilizando a linguagem de programação Java. Como ambiente de desenvolvimento foi utilizado a IDE (Integrated Development Environment) Netbeans 7.1, e a JDK 7.3 (Java Development Kit). Os quatro sistemas foram implementados e estão disponibilizados gratuitamente no site NeuroForest (http://neuroforest.ucoz.com/) e se apresentaram flexíveis e eficientes para a resolução de problemas aos quais se dispõem.

Orientador: Miched Daoud Yacoub / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T17:19:37Z (GMT). No. of bitstreams: 1 Souza_RausleyAdrianoAmaralde_D.pdf: 1070968 bytes, checksum: 289cdc544616610aa8ff990ce2ea0e82 (MD5) Previous issue date: 2009 / Resumo: Em comunicações móveis, o desvanecimento por múltiplos percursos é modelado por várias distribuições incluindo Hoyt, Rayleigh, Weibull, Nakagami-m e Rice. Nesta tese, são deduzidas expressões exatas para o modelo de duas variáveis Hoyt (Nakagami-q) com correlação arbitrária em um ambiente não estacionário. De forma específica, as seguintes estatísticas são encontradas: função densidade de probabilidade conjunta, função de distribuição cumulativa conjunta, coeficiente de correlação e algumas estatísticas relacionadas ao parâmetro SNR na saída do combinador de seleção, a saber, probabilidade de indisponibilidade e função densidade de probabilidade. As expressões fazem uso dos polinômios de Laguerre generalizados. Elas são matematicamente tratáveis e possuem flexibilidade suficiente para acomodar um grande número de cenários de correlação, úteis na análise de um ambiente com desvanecimento mais geral. Depois disto, aproveitando os resultados previamente deduzidos, expressões exatas relacionadas a processos Nakagami-m com duas variáveis com correlação arbitrária e parâmetros de desvanecimento igualmente arbitrários são encontradas. De forma mais específica, as seguintes estatísticas são obtidas neste trabalho: função geratriz de momentos, função densidade de probabilidade conjunta, função de distribuição cumulativa conjunta, coeficiente de correlação de potência, e várias estatísticas ligadas à relação sinal-ruído na saída do combinador de seleção, especialmente, probabilidade de indisponibilidade, função densidade de probabilidade e valor médio da relação sinal-ruído. Recentemente, o modelo de desvanecimento ®-µ foi proposto que leva em conta a não linearidade do meio de propagação assim como o fenômeno de cluster de múltiplos percursos das ondas de rádio. A distribuição ®-µ é geral, flexível e matematicamente tratável. Ela inclui importantes distribuições tais como Gamma (e suas versões discretas Erlang e Chi-Quadrada Central), Nakagami-m (e sua versão discreta Chi), Exponencial, Weibull, Gaussiana Unilateral e Rayleigh. Nesta tese, uma formulação através de série infinita para a função densidade de probabilidade multivariável ®-µ com matriz de correlação arbitrária e variáveis não identicamente distribuídas é encontrada. A expressão é exata e geral e inclui todos os resultados anteriormente publicados na literatura relacionados às distribuições compreendidas pela distribuição ®-µ. A expressão geral é então particularizada para uma solução aproximada simples na forma fechada. Adicionalmente, a função distribuição cumulativa conjunta multivariável é obtida, novamente, em uma forma fechada e simples. Os resultados exato e aproximado são muito próximos para valores pequenos e médio de correlação. Nós mantemos, entretanto, que uma relação entre os coeficientes de correlação das correspondentes componentes gaussianas deve ser mantida de forma a atender os critérios de convergência / Abstract: In wireless communications, the multipath fading is modeled by several distributions including Hoyt, Rayleigh, Weibull, Nakagami-m, and Rice. In this thesis, new, exact expressions for the bivariate Hoyt (Nakagami-q) processes with arbitrary correlation in a nonstationary environment are derived. More specifically, the following are obtained: joint probability density function, joint cumulative distribution function, power correlation coefficient, and some statistics related to the signal-tonoise ratio at the output of the selection combiner, namely, outage probability and probability density function. The expressions make use of the well known generalized Laguerre polynomials. They are mathematically tractable and flexible enough to accommodate a myriad of correlation scenarios, useful in the analysis of a more general fading environment. After this, capitalizing on result previously deduced, exact expressions concerning the bivariate Nakagami-mprocesses with arbitrary correlation and fading parameters are derived. More specifically, the following are obtained in the present work: joint moment generating function; joint probability density function; joint cumulative distribution function; power correlation coefficient; and several statistics related to the signal-to-noise ratio at the output of the selection combiner, namely, outage probability, probability density function, and mean SNR. More recently, the ®-µ fading model has been proposed that accounts for the non-linearity of the propagation medium as well as for the multipath clustering of the radio waves. The ®-µ distribution is general, flexible, and mathematically easily tractable. It includes important distributions such as Gamma (and its discrete versions Erlang and Central Chi-Squared), Nakagami-m (and its discrete version Chi), Exponential, Weibull, One-Side Gaussian, and Rayleigh. An infinite series formulation for the multivariate ®-µ joint probability density function with arbitrary correlation matrix and non-identically distributed variates is derived. The expression is exact and general and includes all of the results previously published in the literature concerning the distributions comprised by the ®-µ distribution. The general expression is then particularized to an indeed very simple, approximate closed-form solution. In addition, a multivariate joint cumulative distribution function is obtained, again in simple, closed-form manner. Approximate and exact results are very close to each other for small as well medium values of correlation. We maintain, however, that a relation among the correlation coefficients of the corresponding Gaussian components must be kept so that convergence is attained / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

La législation sur les émissions de polluants des Moteurs à Combustion Interne (ICEs) est de plus en plus contraignante et représente un gros défi pour les constructeurs automobiles. De nouvelles stratégies de combustion telles que la Combustion à Allumage par Compression Homogène (HCCI) et l’exploitation de stratégies d’injections multiples sont des voies prometteuses qui permettent de respecter les normes sur les émissions de NOx et de suies, du fait que la combustion a lieu dans un mélange très dilué et par conséquent à basse température. Ces aspects demandent la création d’outils numériques adaptés à ces nouveaux défis. Cette thèse présente le développement d’un nouveau modèle 0D de combustion Diesel HCCI : le dual Combustion Model (dual - CM). Le modèle dual-CM a été basé sur l’approche PCM-FPI utilisée en Mécanique des Fluides Numérique (CFD) 3D, qui permet de prédire les caractéristiques de l’auto-allumage et du dégagement de chaleur de tous les modes de combustion Diesel. Afin d’adapter l’approche PCM-FPI à un formalisme 0D, il est fondamental de décrire précisément le mélange à l’intérieur du cylindre. Par consequent, des modèles d’évaporation du carburant liquide, de formation de la zone de mélange et de variance de la fraction de mélange, qui permettent d’avoir une description détaillée des proprietés thermochimiques locales du mélange y compris pour des configurations adoptant des stratégies d’injections multiples, sont proposés. Dans une première phase, les résultats du modèle ont été comparés aux résultats du modèle 3D. Ensuite, le modèle dual-CM a été validé sur une grande base de données expérimentales; compte tenu du bon accord avec l’expérience et du temps de calcul réduit, l’approche présentée s’est montrée prometteuse pour des applications de type simulation système. Pour conclure, les limites des hypothèses utilisées dans dual-CM ont été investiguées et des perspectives pour les dévélopements futurs ont été proposées. / More and more stringent restrictions concerning the pollutant emissions of Internal Combustion Engines (ICEs) constitute a major challenge for the automotive industry. New combustion strategies such as Homogeneous Charge Compression Ignition (HCCI) and the implementation of complex injection strategies are promising solutions for achieving the imposed emission standards as they permit low NOx and soot emissions, via lean and highly diluted combustions, thus assuring low combustion temperatures. This requires the creation of numerical tools adapted to these new challenges. This Ph.D presents the development of a new 0D Diesel HCCI combustion model : the dual Combustion Model (dual−CM ). The dual-CM is based on the PCM-FPI approach used in 3D CFD, which allows to predict the characteristics of Auto-Ignition and Heat Release for all Diesel combustion modes. In order to adapt the PCM-FPI approach to a 0D formalism, a good description of the in-cylinder mixture is fundamental. Consequently, adapted models for liquid fuel evaporation, mixing zone formation and mixture fraction variance, which allow to have a detailed description of the local thermochemical properties of the mixture even in configurations adopting multiple injection strategies, are proposed. The results of the 0D model are compared in an initial step to the 3D CFD results. Then, the dual-CM is validated against a large experimental database; considering the good agreement with the experiments and low CPU costs, the presented approach is shown to be promising for global engine system simulations. Finally, the limits of the hypotheses made in the dual-CM are investigated and perspectives for future developments are proposed.

L'imagerie intravasculaire ultrasonore (IVUS) est une technologie médicale par cathéter qui produit des images de coupe des vaisseaux sanguins. Elle permet de quantifier et d'étudier la morphologie de plaques d'athérosclérose en plus de visualiser la structure des vaisseaux sanguins (lumière, intima, plaque, média et adventice) en trois dimensions. Depuis quelques années, cette méthode d'imagerie est devenue un outil de choix en recherche aussi bien qu'en clinique pour l'étude de la maladie athérosclérotique. L'imagerie IVUS est par contre affectée par des artéfacts associés aux caractéristiques des capteurs ultrasonores, par la présence de cônes d'ombre causés par les calcifications ou des artères collatérales, par des plaques dont le rendu est hétérogène ou par le chatoiement ultrasonore (speckle) sanguin. L'analyse automatisée de séquences IVUS de grande taille représente donc un défi important. Une méthode de segmentation en trois dimensions (3D) basée sur l'algorithme du fast-marching à interfaces multiples est présentée. La segmentation utilise des attributs des régions et contours des images IVUS. En effet, une nouvelle fonction de vitesse de propagation des interfaces combinant les fonctions de densité de probabilité des tons de gris des composants de la paroi vasculaire et le gradient des intensités est proposée. La segmentation est grandement automatisée puisque la lumière du vaisseau est détectée de façon entièrement automatique. Dans une procédure d'initialisation originale, un minimum d'interactions est nécessaire lorsque les contours initiaux de la paroi externe du vaisseau calculés automatiquement sont proposés à l'utilisateur pour acceptation ou correction sur un nombre limité d'images de coupe longitudinale. La segmentation a été validée à l'aide de séquences IVUS in vivo provenant d'artères fémorales provenant de différents sous-groupes d'acquisitions, c'est-à-dire pré-angioplastie par ballon, post-intervention et à un examen de contrôle 1 an suivant l'intervention. Les résultats ont été comparés avec des contours étalons tracés manuellement par différents experts en analyse d'images IVUS. Les contours de la lumière et de la paroi externe du vaisseau détectés selon la méthode du fast-marching sont en accord avec les tracés manuels des experts puisque les mesures d'aire sont similaires et les différences point-à-point entre les contours sont faibles. De plus, la segmentation par fast-marching 3D s'est effectuée en un temps grandement réduit comparativement à l'analyse manuelle. Il s'agit de la première étude rapportée dans la littérature qui évalue la performance de la segmentation sur différents types d'acquisition IVUS. En conclusion, la segmentation par fast-marching combinant les informations des distributions de tons de gris et du gradient des intensités des images est précise et efficace pour l'analyse de séquences IVUS de grandes tailles. Un outil de segmentation robuste pourrait devenir largement répandu pour la tâche ardue et fastidieuse qu'est l'analyse de ce type d'images. / Intravascular ultrasound (IVUS) is a catheter based medical imaging technique that produces cross-sectional images of blood vessels. These images provide quantitative assessment of the vascular wall, information about the nature of atherosclerotic lesions as well as the plaque shape and size. Over the past few years, this medical imaging modality has become a useful tool in research and clinical applications, particularly in atherosclerotic disease studies. However, IVUS imaging is subject to catheter ring-down artifacts, missing vessel parts due to calcification shadowing or side-branches, heterogeneously looking plaques and ultrasonic speckle from blood. The automated analysis of large IVUS data sets thus represents an important challenge. A three-dimensional segmentation algorithm based on the multiple interface fast-marching method is presented. The segmentation is based on region and contour features of the IVUS images: a new speed fonction for the interface propagation that combines the probability density functions (PDFs) of the vessel wall components and the intensity gradients is proposed. The segmentation is highly automated with the detection of the lumen boundary that is fully automatic. Minimal interactions are necessary with a novel initialization procedure since initial contours of the external vessel wall border are also computed automatically on a limited number of longitudinal images and then proposed to the user for acceptance or correction. The segmentation method was validated with in-vivo IVUS data sets acquired from femoral arteries. This database contained 3 subgroups: pullbacks acquired before balloon angioplasty, after the intervention and at a 1 year follow-up examination. Results were compared with validation contours that were manually traced by different experts in IVUS image analysis. The lumen and external wall boundaries detected with the fast-marching method are in agreement with the experts' manually traced contours with similarly found area measurements and small point-to-point contour differences. In addition, the 3D fast-marching segmentation method dramatically reduced the analysis time compared to manual tracing. Such a valdiation study, with comparison between pre- and post-intervention data, has never been reported in the IVUS segmentation literature. In conclusion, the fast-marching method combining the information on the gray level distributions and intensity gradients of the images is precise and efficient to analyze large IVUS sequences. It is hoped that the fast-marching method will become a widely used tool for the fastidious and difficult task of IVUS image processing.

Long-term omni-directional ambient noise was collected at several sites in the Gulf of Mexico during 2004 and 2005. The Naval Oceanographic Office deployed bottom moored Environmental Acoustic Recording System (EARS) buoys approximately 159 nautical miles south of Panama City, Florida, in water depths of 3200 meters. The hydrophone of each buoy was 265 meters above the bottom. The data duration ranged from 10-14 months. The buoys were located near a major shipping lane, with an estimated 1.5 to 4.5 ships per day passing nearby. The data were sampled at 2500 Hz and have a bandwidth of 10-1000 Hz. Data are processed in eight 1/3-octave frequency bands, centered from 25 to 950 Hz, and monthly values of the following statistical quantities are computed from the resulting eight time series of noise spectral level: mean, median, standard deviation, skewness, kurtosis and coherence time. Four hurricanes were recorded during the summer of 2004 and they have a major impact on all of the noise statistics. Noise levels at higher frequencies (400-950 Hz) peak during extremely windy months (summer hurricanes and winter storms). Standard deviation is least in the region 100-200 Hz but increases at higher frequencies, especially during periods of high wind variability (summer hurricanes). Skewness is positive from 25-400 Hz and negative from 630-950 Hz. Skewness and kurtosis are greatest near 100 Hz. Coherence time is low in shipping bands and high in weather bands, and it peaks during hurricanes. The noise coherence is also analyzed. The 14-month time series in each 1/3- octave band is highly correlated with other 1/3-octave band time series ranging from 2 octaves below to 2 octaves above the band's center frequency. Spatial coherence between hydrophones is also analyzed for hydrophone separations of 2.29, 2.56 and 4.84 km over a 10-month period. The noise field is highly coherent out to the maximum distance studied, 4.84 km. Additionally, fluctuations of each time series are analyzed to determine time scales of greatest variability. The 14-month data show clearly that variability occurs primarily over three time scales: 7-22 hours (shipping-related), 56-282 hours (2-12 days, weather-related) and over an 8-12 month period.

L'imagerie intravasculaire ultrasonore (IVUS) est une technologie médicale par cathéter qui produit des images de coupe des vaisseaux sanguins. Elle permet de quantifier et d'étudier la morphologie de plaques d'athérosclérose en plus de visualiser la structure des vaisseaux sanguins (lumière, intima, plaque, média et adventice) en trois dimensions. Depuis quelques années, cette méthode d'imagerie est devenue un outil de choix en recherche aussi bien qu'en clinique pour l'étude de la maladie athérosclérotique. L'imagerie IVUS est par contre affectée par des artéfacts associés aux caractéristiques des capteurs ultrasonores, par la présence de cônes d'ombre causés par les calcifications ou des artères collatérales, par des plaques dont le rendu est hétérogène ou par le chatoiement ultrasonore (speckle) sanguin. L'analyse automatisée de séquences IVUS de grande taille représente donc un défi important. Une méthode de segmentation en trois dimensions (3D) basée sur l'algorithme du fast-marching à interfaces multiples est présentée. La segmentation utilise des attributs des régions et contours des images IVUS. En effet, une nouvelle fonction de vitesse de propagation des interfaces combinant les fonctions de densité de probabilité des tons de gris des composants de la paroi vasculaire et le gradient des intensités est proposée. La segmentation est grandement automatisée puisque la lumière du vaisseau est détectée de façon entièrement automatique. Dans une procédure d'initialisation originale, un minimum d'interactions est nécessaire lorsque les contours initiaux de la paroi externe du vaisseau calculés automatiquement sont proposés à l'utilisateur pour acceptation ou correction sur un nombre limité d'images de coupe longitudinale. La segmentation a été validée à l'aide de séquences IVUS in vivo provenant d'artères fémorales provenant de différents sous-groupes d'acquisitions, c'est-à-dire pré-angioplastie par ballon, post-intervention et à un examen de contrôle 1 an suivant l'intervention. Les résultats ont été comparés avec des contours étalons tracés manuellement par différents experts en analyse d'images IVUS. Les contours de la lumière et de la paroi externe du vaisseau détectés selon la méthode du fast-marching sont en accord avec les tracés manuels des experts puisque les mesures d'aire sont similaires et les différences point-à-point entre les contours sont faibles. De plus, la segmentation par fast-marching 3D s'est effectuée en un temps grandement réduit comparativement à l'analyse manuelle. Il s'agit de la première étude rapportée dans la littérature qui évalue la performance de la segmentation sur différents types d'acquisition IVUS. En conclusion, la segmentation par fast-marching combinant les informations des distributions de tons de gris et du gradient des intensités des images est précise et efficace pour l'analyse de séquences IVUS de grandes tailles. Un outil de segmentation robuste pourrait devenir largement répandu pour la tâche ardue et fastidieuse qu'est l'analyse de ce type d'images. / Intravascular ultrasound (IVUS) is a catheter based medical imaging technique that produces cross-sectional images of blood vessels. These images provide quantitative assessment of the vascular wall, information about the nature of atherosclerotic lesions as well as the plaque shape and size. Over the past few years, this medical imaging modality has become a useful tool in research and clinical applications, particularly in atherosclerotic disease studies. However, IVUS imaging is subject to catheter ring-down artifacts, missing vessel parts due to calcification shadowing or side-branches, heterogeneously looking plaques and ultrasonic speckle from blood. The automated analysis of large IVUS data sets thus represents an important challenge. A three-dimensional segmentation algorithm based on the multiple interface fast-marching method is presented. The segmentation is based on region and contour features of the IVUS images: a new speed fonction for the interface propagation that combines the probability density functions (PDFs) of the vessel wall components and the intensity gradients is proposed. The segmentation is highly automated with the detection of the lumen boundary that is fully automatic. Minimal interactions are necessary with a novel initialization procedure since initial contours of the external vessel wall border are also computed automatically on a limited number of longitudinal images and then proposed to the user for acceptance or correction. The segmentation method was validated with in-vivo IVUS data sets acquired from femoral arteries. This database contained 3 subgroups: pullbacks acquired before balloon angioplasty, after the intervention and at a 1 year follow-up examination. Results were compared with validation contours that were manually traced by different experts in IVUS image analysis. The lumen and external wall boundaries detected with the fast-marching method are in agreement with the experts' manually traced contours with similarly found area measurements and small point-to-point contour differences. In addition, the 3D fast-marching segmentation method dramatically reduced the analysis time compared to manual tracing. Such a valdiation study, with comparison between pre- and post-intervention data, has never been reported in the IVUS segmentation literature. In conclusion, the fast-marching method combining the information on the gray level distributions and intensity gradients of the images is precise and efficient to analyze large IVUS sequences. It is hoped that the fast-marching method will become a widely used tool for the fastidious and difficult task of IVUS image processing.

Cette thèse a pour objet la simulation d'une zone de mélange turbulente issue de l'instabilité de Richtmyer-Meshkov à l'aide d'un modèle à fonction de densité de probabilité (PDF). Nous analysons plus particulièrement la prise en charge par le modèle PDF du transport de l'énergie cinétique turbulente dans la zone de mélange.Dans cette optique, nous commençons par mettre en avant le lien existant entre les statistiques en un point de l'écoulement et ses conditions initiales aux grandes échelles. Ce lien s'exprime à travers le principe de permanence des grandes échelles, et permet d'établir des prédictions pour certaines grandeurs de la zone de mélange, telles que son taux de croissance ou son anisotropie.Nous dérivons ensuite un modèle PDF de Langevin capable de restituer cette dépendance aux conditions initiales. Ce modèle est ensuite validé en le comparant à des résultats issus de simulations aux grandes échelles (LES).Enfin, une analyse asymptotique du modèle proposé permet d'éclairer notre compréhension du transport turbulent. Un régime de diffusion est mis en évidence, et l'expression du coefficient de diffusion associé à ce régime atteste l'influence de la permanence des grandes échelles sur le transport turbulent.Tout au long de cette thèse, nous nous sommes appuyés sur des résultats issus de simulations de Monte Carlo du modèle de Langevin. A cet effet, nous avons développé une méthode spécifique eulérienne et à l'avons comparé à des alternatives lagrangiennes. / The aim of the thesis is to simulate a turbulent mixing zone resulting from the Richtmyer-Meshkov instability using a probability density function (PDF) model. An emphasis is put on the analysis of the turbulent kinetic energy transport.To this end, we first highlight the link existing between the one-point statistics of the flow and its initial conditions at large scales. This link is expressed through the principle of permanence of large eddies, and allows to establish predictions for quantities of the mixing zone, such as its growth rate or its anisotropy.We then derive a Langevin PDF model which is able to reproduce this dependency of the statistics on the initial conditions. This model is then validated by comparing it against large eddy simulations (LES).Finally, an asymptotic analysis of the derived model helps to improve our understanding of the turbulent transport. A diffusion regime is identified, and the expression of the diffusion coefficient associated with this regime confirms the influence of the permanence of large eddies on the turbulent transport.Throughout this thesis, our numerical results were based on Monte Carlo simulations for the Langevin model. In this regard, we proceeded to the development of a specific Eulerian method and its comparison with Lagrangian counterparts.

La capa límit atmosfèrica és l'àrea directament influenciada per la presència de la superfície de la terra i la seva alçada és d'uns centenars de metres a uns pocs quilòmetres. Durant el vespre, el refredament radiatiu estratifica establement l'aire prop del sòl i es forma el que es coneix com a Capa Límit Estable (CLE). D'avui en dia, la CLE és un règim que encara no està prou ben caracteritzat. La turbulència, que no és homogènia ni isòtropa, i la gran importància dels efectes locals com l'orografia, entre d'altres factors, dificulten l'estudi d'aquest règim. Per aquest motiu, la CLE és objecte d'especial atenció, sobretot a l'hora de millorar la seva representació en models tant de temps com de clima.Aquest treball es centra en l'estudi de la CLE mitjançant 3 eines diferents: 1) simulacions explícites de grans remolins (més conegudes com a simulacions LES), per determinar el comportament dels moviments turbulents, on les resolucions són de l'ordre de metres; 2) simulacions mesoscalars, per caracteritzar els efectes locals, on les resolucions són de l'ordre de kilòmetres; 3) anàlisi de les observacions sota aquestes condicions per tal de caracteritzar i entendre millor els fenòmens observats.En primer lloc s'estudia el rang d'estabilitats a on el model LES, que considera la teoria de Kolmogorov per la dissipació de l'energia, funciona correctament. Els resultats del model són realistes tal com mostra la seva comparació amb les mesures de dues campanyes experimentals (SABLES-98 i CASES-99). Per explorar més a fons els resultats LES i per comparar-los amb les mesures s'han utilitzat les Funcions de Distribució de Probabilitat (PDF). Aquests resultats LES són també comparables als obtinguts amb altres models LES, tal com mostra la intercomparació de models LES, més coneguda com a GABLS.Un cop desenvolupades totes les eines necessàries es fa un LES d'un cas més realista, basat en les observacions d'un màxim de vent de capes baixes (més conegut com a Low-Level Jet, LLJ). L'anàlisi combinat dels resultats LES i les mesures permet entendre millor els processos de barreja que tenen lloc a través de la inversió. Finalment, la contribució dels efectes locals s'estudia mitjançant les simulacions mesoscalars, en aquest cas centrades a l'illa de Mallorca. Durant el vespre es veu com les circulacions locals es desenvolupen a les conques (de longitud al voltant de 25km), formant-se, per exemple, vents catabàtics o LLJ com l'estudiat anteriorment. En aquest cas les simulacions es verifiquen amb imatges de satèl·lit NOAA i observacions de les estacions automàtiques de mesures, donant resultats semblants. / The atmospheric boundary layer is the area directly influenced by the presence of the Earth's surface and its height is from hundreds of meters to few kilometres. During the night, the radiative cooling stratifies the layer close to the surface and it forms the Stably-stratified Atmospheric Boundary Layer (SBL). Nowadays, the SBL is a regime not well enough characterized, yet. Turbulence, which is not homogeneous either isotropic, and the great importance of the local effects, like the orography, among other factors, make the SBL be a difficult regime to study. Even so, the SBL is an object of special attention, especially when improving its representation in numerical prediction models or climate models.This work focuses on the study of the SBL through 3 different tools: 1) Large-Eddy Simulations (LES), to determine the turbulent motions, where the resolutions are about 1m; 2) Mesoscale simulations, to characterize the local effects, where resolutions are about 1km; 3) Analysis of the observations under these conditions in order to better characterize and understand the observed phenomena.In first place, it is studied the range of stabilities where the LES model, that considers the Kolmogorov theory for the dissipation of the energy, works correctly. The results are realistic as the comparison with measures from two experimental campaigns (SABLES-98 and CASES-99) shows. To explore the results more thoroughly, and to compare the LES results to the measurements, the Probability Density Functions (PDF) have been used. The LES results are also comparable to the ones obtained with other LES models, as the intercomparison of different LES models show, better known as GABLS.Then, a more realistic case is performed using the LES model, based on observations of a Low-Level Jet (LLJ). The combined inspection of the LES results and the observations allow to better understand the mixing processes that take place through the inversion layer. Finally, the contribution of the local effects is studied through a mesoscale simulation. Here the attention is focused on the Mallorca Island. During the night, the model is able to reproduce the local circulations is a basin of a characteristic size of 25km. The main features obtained previously from the LES of the LLJ are also reproduced by the mesoscale model. These runs are verified with NOAA satellite images and observations from the automatic surface weather stations, giving that the model is able to reproduce realistic results.

[ES] El proyecto ESTiMatE nace con el objetivo de mejorar la precisión de las predicciones de hollín para la reducción de emisiones y una mayor sostenibilidad ambiental en la aviación. Para ello es crucial comprender a fondo fenómenos que influyen en la formación de hollín, incluyendo atomización del combustible, mezcla, combustión y formación de emisiones. La presente tesis, como parte del proyecto, se centra en el primer paso para caracterizar las spray flames, el proceso de atomización del líquido. Existen modelos empíricos para ello, pero el objetivo de este trabajo es desarrollar un nuevo modelo fenomenológico a través de simulaciones de alta fidelidad. Se propone acoplar este modelo a los códigos PRECISE-UNS y Alya para inyectar gotas en simulaciones Lagrangianas, reproduciendo de forma efectiva las características clave de atomización primaria en la formación del spray. Realizar estudios sobre la configuración anular de atomizadores prefilming airblast es un gran desafío, por lo que los esfuerzos se han enfocado en la configuración plana como alternativa que proporciona información valiosa. El KIT ha hecho contribuciones notables en este sentido al desarrollar un banco de pruebas de configuración plana, generando una base de datos extensa con resultados que abarcan diversos fluidos de trabajo y condiciones de operación para validar los cálculos. Esta tesis investiga la atomización primaria en estos dispositivos con un enfoque computacional a través de simulaciones eDNS con el código PARIS Simulator. Se utilizan simulaciones VOF-DNS del borde del atomizador para obtener información, y simulaciones LES monofásicas precursoras que permiten tener en cuenta la turbulencia del gas en la entrada. No obstante, se han propuesto dos metodologías derivadas a partir de eDNS, extendiéndola con simulaciones LES bifásicas adicionales. La primera de ellas impone un espesor y velocidad constantes para la película líquida en la entrada, pero sus valores medios se obtienen procesando las nuevas simulaciones LES bifásicas. Esta metodología ha sido validada para una condición de operación de referencia, representativa del reencendido en altitud. La segunda, introduce un espesor y velocidad variables de la película líquida, constituyendo una condición de contorno más realista. Se han realizado dos estudios diferentes. Por un lado, utilizando la primera metodología, se realizó un estudio paramétrico para investigar el impacto de la velocidad media del gas y las propiedades del fluido en la formación de estructuras líquidas. Al variar estos parámetros se observan diferencias en los mecanismos de ruptura basadas en M como en la literatura. La base para un modelo fenomenológico se ha establecido utilizando estos resultados y puede extenderse con más condiciones de operación siguiendo la metodología descrita. Por otra parte, se ha realizado una comparación entre ambas metodologías para considerar la influencia de la historia de la película de combustible en la atomización primaria. En este estudio, al mejorar las condiciones de contorno a la entrada, se ha reproducido con éxito la fenomenología presente en los experimentos, al contrario que con la eDNS estándar. Se ha propuesto una nueva técnica de postprocesado para caracterizar las estructuras líquidas. Los métodos habituales detectan gotas en un dominio 3D, pero solamente detectan ligamentos en una proyección 2D utilizando optimización de funciones algebraicas. Sin embargo, este nuevo método es capaz de encontrar gotas y ligamentos en 3D mediante OpenCV. También ha sido validado con resultados de la literatura. Con todo, la tesis ha sentado las bases para el desarrollo de modelos específicos de atomización airblast mediante simulaciones de alta fidelidad, contribuyendo a una mejor predicción de los fenómenos de inyección, atomización, evaporación, mezcla y combustión de aeromotores que permita realizar un diseño más eficiente de éstos hacia una movilidad aérea sostenible. / [CA] El projecte ESTiMatE naix amb l'objectiu de millorar la precisió de les prediccions de sutge per a la reducció d'emissions i una major sostenibilitat ambiental en l'aviació. Per això, és crucial comprendre a fons fenòmens que influeixen en la formació de sutge, incloent atomització del combustible, mescla, combustió i formació d'emissions. La present tesi, com a part del projecte, se centra en el primer pas per caracteritzar les spray flames, el procés d'atomització del líquid. Existeixen alguns models empírics per això, però l'objectiu d'aquest treball és desenvolupar un nou model fenomenològic a través de simulacions d'alta fildelitat. Es proposa acoblar aquest model als codis PRECISE-UNS i Alya per injectar gotes en simulacions Lagrangianes, reproduint de manera efectiva les característiques clau d'atomització primària en la formació de l'spray. Realitzar estudis sobre la configuració anul·lar d'atomitzadors prefilming airblast és un gran desafiament, per la qual cosa els investigadors han enfocat els seus esforços en la configuració plana com alternativa que proporciona informació valuosa. El KIT ha fet contribucions notables en aquest sentit en desenvolupar un banc de proves de configuració plana, generant una base de dades extensa amb resultats que abasten diversos fluids de treball i condicions d'operació per a validar els càlculs. Esta tesi investiga l'atomització primària en aquests dispositius amb un enfocament computacional a través de simulacions eDNS emprant el codi PARIS Simulator. S'utilitzen simulacions VOF-DNS de la vora de l'atomitzador per a obtindre informació, i simulacions LES monofàsiques precursores que permeten tindre en compte la turbulència del gas a l'entrada. No obstant això, s'han proposat dues noves metodologies derivades a partir de eDNS, estenent-la amb simulacions LES bifàsiques addicionals. La primera d'elles imposa una grossària i velocitat constants per a la pel·lícula líquida en l'entrada, però els seus valors mitjans s'obtenen processant les noves simulacions LES bifàsiques. Aquesta metodologia ha sigut validada per a una condició d'operació de referència, representativa de la reencesa en altitud. La segona, introduïx una grossària i velocitat variables de la pel·lícula líquida, constituint una condició de contorn més realista. S'han realitzat dos estudis diferents. D'una banda, utilitzant la primera metodologia, es va realitzar un estudi paramètric per a investigar l'impacte de la velocitat mitjana del gas i les propietats del fluid en la formació d'estructures líquides. En variar estos paràmetres s'observen diferènciesen els mecanismes de ruptura basades en M com a la literatura. La base per a un model fenomenològic s'ha establit utilitzant aquests resultats i pot estendre's amb més condicions d'operació seguint la metodologia descrita. D'altra banda, s'ha realitzat en paral·lel una comparació entre totes dues metodologies per a considerar la influència de la història de la pel·lícula de combustible en l'atomització primària. En aquest estudi, en millorar les condicionsde contorn a l'entrada, s'ha reproduït amb èxit la fenomenologia present en els experiments, al contrari que amb la eDNS estàndard. S'ha proposat una nova tècnica de postprocessament per a caracteritzar les estructures líquides. Els mètodes habituals detecten gotes en un domini 3D, però solament detecten lligaments en una projecció 2D utilitzant optimització de funcions algebraiques. No obstant això, aquest nou mètode és capaç de trobar gotes i lligaments en 3D mitjançant la llibrería OpenCV. També ha sigut validat amb resultats de la literatura. Amb tot, la tesi ha establit les bases per al desenvolupament de models específics d'atomització airblast mitjançant simulacions d'alta fidelitat, contribuïnt a una millor predicció dels fenòmens d'injecció, atomització, evaporació, mescla i combustió dels aeromotors que permeta realitzar un disseny més eficient dels mateixos cap a una mobilitat aèria sostenible. / [EN] The project ESTiMatE emerges aiming to enhance the precision of soot predictions leading to reduced emissions and improved environmental sustainability in aviation. To achieve this, it is crucial to thoroughly understand various phenomena that influence soot formation, including fuel atomization, mixing, combustion, and subsequent emissions formation. The present thesis, as part of the project, focuses in the first step to characterize spray flames, the liquid atomization process. There exist some empirical models to characterize atomization, but the objective of this specific work package is to develop a new phenomenological model through high-fidelity simulations instead of empirical results. This model is proposed to be coupled to the PRECISE-UNS and Alya codes to inject droplets in Lagrangian simulations, effectively reproducing the key features of the primary atomization process on the spray formation. Conducting fundamental studies on the annular configuration of prefilming airblast atomizers is challenging, so researchers have directed their attention towards planar configurations as an alternative that can provide valuable insights. The KIT has made notable contributions in this regard by developing a dedicated planar test rig, generating a substantial database of results encompassing various working fluids and operating conditions for validation. This thesis investigates primary atomization in these devices with a computational approach using eDNS within the PARIS Simulator code. VOF-DNS simulations of the atomizing Edge are performed to obtain useful data, and precursor one-phase LES simulations in order to account for gas inflow turbulence at the DNS inlet. Nevertheless, two methodologies have been derived from eDNS, extending it with additional precursor two-phase LES simulations. The first one, imposes constant liquid film thickness and velocity at the DNS inlet, but their mean values are obtained processing the new two-phase LES simulations. It has been validated for a reference operating condition, representative of altitude relight. The second one, introduces variable liquid film thickness and velocity instead, constituting a more realistic boundary condition for the DNS. Two different studies have been conducted in this regard. On the one hand, using the former methodology, a parametric study was performed to investigate the impact of mean gas velocity and fluid properties on the formation of liquid structures. By varying these parameters differences on the breakup mechanisms are observed based on M as found in the literature. The basis for a phenomenological model has been established using these results, and it can be extended with more operating conditions following the described methodology. On the other hand, a comparison between both methodologies has been carried out in parallel, in order to account for the influence of film history on the primary atomization process. In this study, by improving the inlet boundary conditions, the phenomenology observed in the experiments has been succesfully reproduced, unlike with the standard eDNS. A novel post-processing technique for characterizing liquid structures has been proposed. Usual post-processing methods detect droplets in a 3D domain, but only detect ligaments in a top view 2D projection of it using algebraic functions optimization. However, this new method is able to find both droplets and ligaments as well as its 3D properties using the Open Computer Vision Library (OpenCV) instead. It has been also validated with the results in the literature. Overall, the thesis has laid the foundations for the development of specific airblast atomization models through the use of high-fidelity simulations,contributing to a better prediction of the injection, atomization, evaporation, mixing and combustion phenomena in aero engines, enabling a more efficient design towards sustainable air mobility. / Moreno Montagud, C. (2024). Computational Modelling of the Primary Atomization in Aero Engine Airblast Atomizers through a DNS Approach [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/211359