Esta tese objetiva caracterizar o escoamento provocado pela incidência de um jato vertical em um fundo plano, descrevendo assim as características médias e flutuantes das pressões a partir da investigação experimental. O modelo utilizado é composto por um jato retangular posicionado, perpendicularmente, a uma distância de 0,92 m do fundo plano de um canal. Utilizando transdutores de pressão instalados na posição de incidência do jato, adquiriu-se os valores de pressão “instantânea” a uma frequência de 128 Hz durante 10 minutos. Foram ensaiadas cinco (5) vazões: 25 l/s (Fr1 = 7,12), 30 l/s (Fr1 = 8,51), 36,6 l/s (Fr1 = 10,35), 42,7 l/s (Fr1 = 12,12) e 50l/s (Fr1 = 14,23), além de vinte (20) diferentes espessuras de colchão d'água. Com os dados de pressão, efetuou-se análises no domínio do tempo, da frequência e da posição. No domínio do tempo, analisou-se a variação dos parâmetros estatísticos essenciais (média, desvio padrão, assimetria e curtose) bem como a identificação de valores máximo e mínimos das pressões. No domínio da frequência, procurou-se avaliar por meio da análise espectral a identificação de frequências significativas associadas à energia macroturbulenta. No que tange à análise no domínio da posição buscou-se analisar a faixa de influência do jato junto ao fundo, a região de subpressões e o alcance das pressões dinâmicas. Outro aspecto importante abordado é a apresentação dos resultados em gráficos adimensionalizados, o que confere ao estudo um caráter geral dentro da faixa de valores ensaiados. Os resultados definem um colchão mínimo de água da ordem de 3 vezes a altura crítica do escoamento, para o amortecimento das pressões dinâmicas. A análise dos momentos estatísticos demonstra que a distribuição das pressões não segue a distribuição normal. Dentro disso, estão disponibilizados coeficientes estatísticos de probabilidade para a determinação das pressões extremas. Ainda, estão definidas quatro zonas a jusante do impacto do jato: Zona I - região do impacto, Zona II - reflexão do jato, Zona III - Acomodação do escoamento e por fim, a Zona IV - caracterizada pelo fim da influência do jato. Além disso, uma análise deste escoamento sob a perspectiva da formação de um ressalto hidráulico é realizada, indicando que apenas os parâmetros utilizados, não descrevem o escoamento como tal. Esta tese é produto da parceria entre Laboratório de Obras Hidráulicas do Instituto de Pesquisas Hidráulicas da Universidade Federal do Rio Grande do Sul (LOH/IPH/UFRGS) e o Laboratório de Hidráulica Experimental e Recursos Hídricos de Furnas Centrais Elétricas S. A. (LAHE/FURNAS). / This thesis aims to characterize the flow prompted by the incidence of a vertical jet on a flat bottom, thus describing the mean and floating characteristics of the pressures from the experimental investigation. The model used is comprised of a rectangular jet positioned perpendicularly at a distance of 0.92 m from the flat bottom of a channel. Using pressure transducers installed in the jet incidence position, the "instantaneous" pressure values were acquired at a frequency of 128 Hz for 10 minutes. Five (5) discharges were tested: 25 l/s (Fr1 = 7.12), 30 l/s (Fr1 = 8.51), 36.6 l/s (Fr1 = 10.35), 42.7 l/s (Fr1 = 12.12) and 50 1/s (Fr1 = 14.23), as well as twenty (20) different waterbed thicknesses. The pressure data were analyzed in terms of time, frequency and position domains. In the time domain, the variation of the essential statistical parameters (mean, standard deviation, asymmetry and kurtosis) was analyzed, as well as the identification of maximum and minimum pressure values. In the frequency domain, it was sought to assess, by means of the spectral analysis, the identification of significant frequencies associated with macroturbulent energy. Regarding the analysis in the position domain, this study aimed to analyze the range of influence of the jet near the bottom, the region of subpressions and the reach of the dynamic pressures. Another important aspect is the presentation of the results in dimensionless graphs, which grants the study a general character within the range of values tested. The results define a minimum waterbed of the order of 3 times the critical height of the flow for the damping of the dynamic pressures. Statistical moments analysis shows that the distribution of pressures does not follow the normal distribution. Therein, probability statistical coefficients are available for the determination of extreme pressures. Also, four zones are defined downstream of the impact of the jet: Zone I - region of impact, Zone II - reflection of the jet, Zone III - accommodation of the flow and, finally, Zone IV - characterized by the end of the influence of the jet. Furthermore, an analysis of this flow from the perspective of the formation of a hydraulic jump is conducted, indicating that the parameters used alone do not describe the flow as such. This thesis is a product of the partnership between the Hydraulic Works Laboratory of the Hydraulic Research Institute of the Federal University of Rio Grande do Sul (LOH/IPH/UFRGS) and the Laboratory of Experimental Hydraulics and Hydraulic Resources of Furnas Centrais Elétricas SA (LAHE/FURNAS).

Esta tese objetiva caracterizar o escoamento provocado pela incidência de um jato vertical em um fundo plano, descrevendo assim as características médias e flutuantes das pressões a partir da investigação experimental. O modelo utilizado é composto por um jato retangular posicionado, perpendicularmente, a uma distância de 0,92 m do fundo plano de um canal. Utilizando transdutores de pressão instalados na posição de incidência do jato, adquiriu-se os valores de pressão “instantânea” a uma frequência de 128 Hz durante 10 minutos. Foram ensaiadas cinco (5) vazões: 25 l/s (Fr1 = 7,12), 30 l/s (Fr1 = 8,51), 36,6 l/s (Fr1 = 10,35), 42,7 l/s (Fr1 = 12,12) e 50l/s (Fr1 = 14,23), além de vinte (20) diferentes espessuras de colchão d'água. Com os dados de pressão, efetuou-se análises no domínio do tempo, da frequência e da posição. No domínio do tempo, analisou-se a variação dos parâmetros estatísticos essenciais (média, desvio padrão, assimetria e curtose) bem como a identificação de valores máximo e mínimos das pressões. No domínio da frequência, procurou-se avaliar por meio da análise espectral a identificação de frequências significativas associadas à energia macroturbulenta. No que tange à análise no domínio da posição buscou-se analisar a faixa de influência do jato junto ao fundo, a região de subpressões e o alcance das pressões dinâmicas. Outro aspecto importante abordado é a apresentação dos resultados em gráficos adimensionalizados, o que confere ao estudo um caráter geral dentro da faixa de valores ensaiados. Os resultados definem um colchão mínimo de água da ordem de 3 vezes a altura crítica do escoamento, para o amortecimento das pressões dinâmicas. A análise dos momentos estatísticos demonstra que a distribuição das pressões não segue a distribuição normal. Dentro disso, estão disponibilizados coeficientes estatísticos de probabilidade para a determinação das pressões extremas. Ainda, estão definidas quatro zonas a jusante do impacto do jato: Zona I - região do impacto, Zona II - reflexão do jato, Zona III - Acomodação do escoamento e por fim, a Zona IV - caracterizada pelo fim da influência do jato. Além disso, uma análise deste escoamento sob a perspectiva da formação de um ressalto hidráulico é realizada, indicando que apenas os parâmetros utilizados, não descrevem o escoamento como tal. Esta tese é produto da parceria entre Laboratório de Obras Hidráulicas do Instituto de Pesquisas Hidráulicas da Universidade Federal do Rio Grande do Sul (LOH/IPH/UFRGS) e o Laboratório de Hidráulica Experimental e Recursos Hídricos de Furnas Centrais Elétricas S. A. (LAHE/FURNAS). / This thesis aims to characterize the flow prompted by the incidence of a vertical jet on a flat bottom, thus describing the mean and floating characteristics of the pressures from the experimental investigation. The model used is comprised of a rectangular jet positioned perpendicularly at a distance of 0.92 m from the flat bottom of a channel. Using pressure transducers installed in the jet incidence position, the "instantaneous" pressure values were acquired at a frequency of 128 Hz for 10 minutes. Five (5) discharges were tested: 25 l/s (Fr1 = 7.12), 30 l/s (Fr1 = 8.51), 36.6 l/s (Fr1 = 10.35), 42.7 l/s (Fr1 = 12.12) and 50 1/s (Fr1 = 14.23), as well as twenty (20) different waterbed thicknesses. The pressure data were analyzed in terms of time, frequency and position domains. In the time domain, the variation of the essential statistical parameters (mean, standard deviation, asymmetry and kurtosis) was analyzed, as well as the identification of maximum and minimum pressure values. In the frequency domain, it was sought to assess, by means of the spectral analysis, the identification of significant frequencies associated with macroturbulent energy. Regarding the analysis in the position domain, this study aimed to analyze the range of influence of the jet near the bottom, the region of subpressions and the reach of the dynamic pressures. Another important aspect is the presentation of the results in dimensionless graphs, which grants the study a general character within the range of values tested. The results define a minimum waterbed of the order of 3 times the critical height of the flow for the damping of the dynamic pressures. Statistical moments analysis shows that the distribution of pressures does not follow the normal distribution. Therein, probability statistical coefficients are available for the determination of extreme pressures. Also, four zones are defined downstream of the impact of the jet: Zone I - region of impact, Zone II - reflection of the jet, Zone III - accommodation of the flow and, finally, Zone IV - characterized by the end of the influence of the jet. Furthermore, an analysis of this flow from the perspective of the formation of a hydraulic jump is conducted, indicating that the parameters used alone do not describe the flow as such. This thesis is a product of the partnership between the Hydraulic Works Laboratory of the Hydraulic Research Institute of the Federal University of Rio Grande do Sul (LOH/IPH/UFRGS) and the Laboratory of Experimental Hydraulics and Hydraulic Resources of Furnas Centrais Elétricas SA (LAHE/FURNAS).

Nous présentons dans ce travail différentes configurations utilisées pour étudier des éxperiences, pertinentes d'un point de vue astrophysique, mettant en jeu des plasma produits par laser ainsi que des champs magnétiques intenses. les outils théoriques et numériques sont d'abord présentés avec la dérivation complète du modèle de magnétohydrodynamique (mhd) résistive à deux températures. nous décrivons aussi les nouveaux modules de physique implémentés au cours de cette thèse. la configuration de base utilisée pour notre travail consiste en une ou plusieurs cibles solides sur lesquelles un laser intense est envoyé dans le but de générer un plasma se propageant dans le vide. on montre que l'ajout d'un champ magnétique de plusieurs dizaines de teslas influence fortement la dynamique de ce plasma et que selon l'orientation initiale du champ, il est possible de générer différentes structures telles que des jets supersonic/superalfvenic ou encore des «crêpes» de plasma. par exemple, les jets ainsi produits sont caractérisés par des régimes tels que des lois d'échelles entre le système du laboratoire et le système astrophysique (jeunes étoiles connues sous le nom de t tauri) sont applicables. un sujet important et inédit traité dans cette thèse concerne la génération de chocs d'accrétion magnétisés en utilisant les jets mentionnés ci-dessus comme flots accrétant sur des cibles solides. nous mettons notamment l'accent, contrairement à la plupart des travaux précédents, sur la structure 3d de ces chocs et els instabilités présentes. pour chaque cas étudié, nous présentons des nouveaux résultats expérimentaux obtenus par notre collaboration sur le laser elfie du luli. / We present in this work different configurations used as a mean to study astrophysically-relevant (by scaling) experiments using laser-produced plasmas and strong magnetic fields. This work is a contribution to the relatively recent field known as high energy density laboratory astrophysics (hedla). The theoretical and numerical framework used in this this work is first introduced with a detailed derivation of the magnetohydrodynamic (mhd) model for bi-temperature and resistive plasmas. The three-dimensional mhd code gorgon and the new physical modules implemented during this thesis are presented. The basic setup studied here involve one or several solid slabs being used as targets for a joule-class laser. The expanding plasma thus produced is embedded in magnetic fields of strengths up to 40 t. Depending on the orientation of the field relative to the target surface, we show that the resulting plasma dynamic, relatively well described by ideal mhd, is strongly modified by the presence of the field. The first topic treated is related to the production, when the field is perpendicular to the target surface, of super-sonic/alfvenic jets relevant in the context of astrophysical jets observed around young star objects (t tauri stars). When the field is oriented parallel to the surface, we show that the configuration results in the formation of thin unstable plasma slabs. We also studied the possibility to generate magnetized accretion shocks in the laboratory and we detail the 3d structure obtained in this case. Alongise the numerical work, we present for each case mentioned previously, new experimental results obtained by the collaboration on the elfie laser facility (luli).

Cette thèse de doctorat a été financée par l’entreprise SIKA spécialisée dans les matériaux de construction. Les trois chapitres de cette thèse correspondent à la tentative de résolution de trois problématiques d’origine industrielle. Dans le premier chapitre, nous avons étudié l’effet de la concentration en particules sur les propriétés d’écoulement de fluides complexes rhéofluidifiants ou rhéoépaississants et démontré l’origine microscopique de cet effet. Dans le second chapitre, nous avons étudié la floculation de particules colloïdales sous faibles perturbations et mis en évidence l’existence, au cours de la reconstruction, d’un maximum du module élastique. Enfin le troisième chapitre est l’étude d’un diagramme de phase de jet de suspensions concentrées. En régime dilué et semi-dilué, les résultats sont conformes à ceux de la bibliographie, en revanche nous avons étudié un nouveau régime à très haute fraction volumique où le jet, instable, se met à osciller. Nous avons montré que ces oscillations étaient dues au rhéoépaississement de la suspension. / This thesis has been done in collaboration with the company SIKA, one of the leader if the construction industry. This thesis report is organized in three chapters where each of them tries to answer a problem coming from industrial processes. In the first chapter, we studied the impact of particles concentration on the flowing properties of complex fluids such as shear-thinning and shear-thickening fluids. We demonstrated the importance of local contacts between particles to explain the evolution of the viscosity with the volume fraction. In the second chapter, we studied the aggregation of colloidal attractive suspensions under small perturbations and proved the existence of a maximum of elastic modulus during the rebuilding of the structure. Finally, the third chapter is a study of a phase diagram of a concentrated suspension jets. In the diluted and semi-diluted regimes, we found results in agreement with the bibliography, meanwhile at very high concentration, we studied a new regime where the jet, unstable, is oscillating. We showed those oscillations can be explained by the shear-thickening behaviour of the suspensions at those high concentrations.

Numerical solutions based on explicit filtered LES for computing turbulent flow field, of free round jets and impinging round jet on cuboidal cavities, are presented and discussed in this dissertation work. One-parameter fourth-order explicit filter is implemented to account for sub-grid scale effects. Compact difference schemes proposed by Hixon & Turkel involving only bidiagonal matrices is used to evaluate spatial derivatives. Compact schemes with overall fourth order accuracy and eight order accuracy are used in simulating free and impinging jets respectively. Simulations of free round jets are used for validating LES approach. 6 simulations of free round jet, in three levels of computational grids at three different Reynolds number, are performed to understand the effects of Reynolds number and turbulent length scales. Energy in the smaller length scales are found to be higher for higher Reynolds number. Potential core collapse is found to occur at shorter distance for high Reynolds number jets. Accurate computation of smaller length scales of turbulence is found to be essential for high Reynolds number flows. LES of subsonic impinging jets are performed on cuboidal cavities to understand the physical phenomenon. High intensity, low frequency sounds are captured, in the presence of cavity, as reported by other research works. Lip-thickness is found to have an effect on the intensity of sound produced. Matching of Jet shear layer roll up frequency with cavity’s natural frequency to produce resonance phenomenon is attempted and observations are presented.

Une étude expérimentale du développement de jets turbulents à masse volumique variable est menée. Les comportements axiaux et radiaux des propriétés statistiques moyennes et fluctuantes obtenues sur les champs de vitesse et de concentration sont analysés. Ces résultats apportent une meilleure compréhension des phénomènes de mélange et de l’effet de la variation de densité dans le but d’apporter des données complémentaires pour le développement des calculs numériques et accroître leurs précisions. Les cas étudiés dans cette thèse sont deux jets d’hélium marqués par de la vapeur d’acétone pour des nombres de Reynolds Re = 7000 et 11000 permettant d’explorer l’effet de fortes variations de masse volumique (S = 0,39 et 0,41, respectivement) par rapport à l’air ambiant. Le cas d’un jet d’air (Re = 16000) également porteur de vapeur d’acétone est utilisé comme cas de référence comparable au cas d’un contaminant passif avec S = 1,17. L’étude porte sur la région de proche sortie de jet, jusqu’à une distance de 40 fois le diamètre Dj de sortie du jet. La configuration adoptée est celle d’un jet de tube rond, libre, axisymétrique, vertical et ascendant dont le diamètre intérieur du tube est Dj = 3,5mm se développant dans l’air ambiant. La particularité de cette étude est la mise en œuvre d’un système de mesure par diagnostic optique qui permet un couplage spatial et temporel des mesures de vitesse et de concentration sur une région de l’écoulement de quelques cm2 et non sur un seul point. Pour ce faire, le couplage des mesures PIV, pour la mesure du champ de vitesse, et PLIF basée sur la fluorescence de la vapeur d’acétone, pour la mesure du champ de concentration, a été étudié, conçu et testé. Il nous a permis d’obtenir une base de données, encore trop rares aujourd’hui, sur l’évolution des flux turbulents croisés de vitesse et concentration. Ces données ont mis en évidence une évolution plus rapide du jet le plus léger. Cependant, les coefficients de corrélation semblent identiques lorsque l’on atteint la zone autosimilaire du jet. Une approche basée sur les probabilités de densité conjointes vitesse-concentration a permis de mettre en évidence des différences dans la région extérieure des jets, où l’intermittence de frontière donne son empreinte sur les propriétés du mélange. / An experimental study of the development of turbulent jets with variable density is presented. The axial and radial behaviours of the mean and fluctuating statistical properties obtained on the velocity and concentration fields are analysed. These results provide a better understanding of mixing phenomena and the effect of density variation in order to provide complementary data for the development of numerical calculations and to increase their precision. The cases studied in this thesis are two helium jets carrying acetone vapor for Reynolds numbers Re = 7000 and 11000 to explore the effect of large density variations (S = 0.39 and 0.41, respectively) relative to the ambient air. The case of an air jet (Re = 16000) also carrying acetone vapor is used as a reference case comparable to the case of a passive contaminant with S = 1.17. The study focuses on the region of near jet exit, up to a distance of 40 times the jet outlet diameter Dj. The adopted configuration is a round jet tube, free, axisymmetric, vertical and ascending whose internal diameter of the tube is Dj = 3.5 mm developing in the ambient air. The particularity of this study is the implementation of an optical diagnostic measurement system that allows a spatial and temporal coupling of speed and concentration measurements over a region of the flow of a few cm2. To do this, the coupling of the PIV measurements for the measurement of the velocity field and the PLIF based on the fluorescence of the acetone vapor for the measurement of the concentration field has been studied, designed and tested. It allowed us to obtain a database, still too rare today, on the evolution of the turbulent flow of speed and concentration. These data have shown a faster evolution of the lightest jet. However, the correlation coefficients appear to be identical when the self-similar zone of the jet is reached. An approach based on joint speed-concentration density probabilities has revealed differences in the outer region of the jets, where the intermittent boundary gives its imprint on the properties of the mixture.

Le Large Hadron Collider (LHC) fonctionne à une énergie dans le centre-de-masse de 13 TeV, atteignant ainsi des énergies bien au-dessus de l'échelle électrofaible. Pour la première fois, des particules lourdes sont produites dans le régime boosté, c'est-à-dire avec une impulsion transverse beaucoup plus grand que leur masse. Leur produits de désintégration hadronique sont collimatés et finisseent par être regroupé dans un seul jet. Dans cette situation, il n'est pas facile de discriminer le signal des particules lourdes du bruit de fond formé par des jets originés par les partons, il faut examiner la dynamique interne du jet avec des techniques de sous-structure des jets. Les outils de la sous-structure de jet sont divisés en trois catégories : « Jet shapes » qui contraient la radiation des gluons mous dans le jet ; « Taggers » qui cherchent plusieurs cœurs d'énergie dans le jet, une situation plus courant dans les jets de signaux que dans les jets QCD ; et les « Groomers » qui éliminent la radiation molle et à grand angle dans le jet, souvent dominés par l'événement sous-jacent.Dans cette thèse, on propose une approche analytique qui nous permet de comprendre les sources des différences de performance entre les méthodes. On utilise des techniques de resommation à tous les ordres en théorie des perturbations, pertinentes pour les régimes bostés où l'échelle de masse et de l'impulsion transverse sont largement séparées. On motive le besoin de resommation et on introduit les éléments de base qui sont utilisés tout au long de la thèse. Cette thèse se concentre sur les jets à deux cœurs, comment les bosons W/Z/H.Premièrement, on explore comment un tagger spécifique, le Y-splitter, peut être combiné avec une variété de techniques de grooming : le MassDrop Tagger (mMDT), trimming et SoftDrop. Selon des études Monte Carlo, cette combinaison augmente la performance du Y-splitter. On explique l’origine de se comportement par des calculs théoriques et étudie l'impact des effets non-perturbatives. On présente également des variantes améliorées de la méthode Y-Splitter originale.Ensuite, on étudie l'utilisation des jet shapes comment une variable discriminante entre les désintégrations hadroniques à deux cœurs des bosons électrofaibles et le bruit de fond des jets QCD. On calcule analytiquement la distribution de masse avec une coupure sur la variable jet shape. On considère 3 shapes couramment utilisées : N-subjettiness, « Energy Correlation functions » et le paramètre MassDrop. Nos résultats expliquent la différence entre les performances des différentes méthodes. On compare également nos résultats aux générateurs de Monte Carlo et on étudie l'impact des effets non-perturbatifs.Notre étude suivant examine la combinaison des techniques de grooming/tagging avec des jet shapes, en particulier le N-subjettiness. On propose le rapport dichroïque de N-subjettiness, où on utilise un gros jet (avec ou sans pre-grooming) pour calculer tau ₂ et un jet plus petit, avec tagging pour tau₁. Cette version donne une performance améliorée par rapport aux versions utilisées actuellement par les expériences, tout en maintenant les effets non-perturbatifs sous contrôle.Enfin, on effectue une étude phénoménologique de la distribution de masse des jets avec mMDT. Ceci est actuellement mesurée par des expériences au LHC. Nos prédictions théoriques prennent en compte les logarithmes dominants du rapport de la masse de jet sur l'impulsion transverse et on fait le « matching » avec les éléments de matrice à ordre fixe calculés au NLO. On discute deux options possibles, selon que les distributions sont mesurées dans des bins de l'impulsion transverse avant ou après le mMDT. / The Large Hadron Collider (LHC) is running at a center-of-mass energy of 13 TeV, thus reaching energies far above the electroweak scale. For the first time, heavy particles are produced in the boosted regime, i.e. with transverse momentum much larger than their mass. Their hadronic decay products are collimated and end up being clustered into a single jet. In this situation is not easy to discriminate the heavy particle signal from the background, formed by jets originated from QCD partons, so one has to examine the internal dynamics of the jet using jet substructure techniques. Jet substructure tools are divided in three main categories: Jet shapes, which constrain soft-gluon radiation inside jets; Taggers which look for multiple hard cores inside the jet, a situation more common in signal jets than in QCD jets; and Groomers which clean the fat jets of soft-and-large-angle radiation, often dominated by the underlying event.This thesis proposes an analytical approach which allows us to understand the sources of performance differences between methods. We will use all-order resummation techniques, relevant for the boosted regime where the mass and transverse-momentum scale are widely separated. We motivate the need for resummation and introduce the basic elements (building blocks) that are used throughout the thesis. In this thesis, we focus on two-pronged jets, like W/Z/H decays.We first study how a specific tagger, namely Y-splitter, can be combined with a variety of grooming techniques: the modified MassDrop Tagger (mMDT), trimming and SoftDrop. It is known from Monte Carlo studies that such combination increases the Y-splitter performance. We study the origin of this behaviour from a theoretical point of view and the impact of non-perturbative effects. We also introduce improved variants of the original Y-splitter method.Next, we study the use jet shapes as a discriminant variable between two-pronged hadronic decays of electroweak bosons and the QCD jets background. We compute analytically the jet mass distribution with an additional cut on the jet shape variable. We obtain results for 3 common shapes: N-subjettiness, Energy Correlation function and MassDrop parameter. Our results explain differences in discriminating power between the shapes. We also compare our results to Monte Carlo generators and study the impact of non-perturbative effects.Our next study investigates the combination of grooming/tagging techniques with jet shapes, in particular N-subjettiness. In this work, we propose the dichroic N-subjettiness ratio, where we use a large jet (with or without a pre-grooming step) for calculating tau ₂ and a smaller, tagged subjet for tau₁. This observable gives an enhanced performance compared to the variants currently used in experimental analyses, while keeping non-perturbative effects under control.Finally, we perform a phenomenological study of the jet mass distribution after applying the mMDT. This is currently being measured by LHC experiments. Our theoretical predictions account for the resummation of the leading-logarithm of the ratio of the jet mass over the jet transverse momentum and it is matched to fixed-order matrix elements computed at next-to-leading order. We discuss two options according to whether the distributions are measured in bins of the jet transverse momentum before or after the mMDT.

La combustion sans flamme est un régime de combustion massivement dilué associant forte efficacité énergétique et très faibles émissions polluantes dans les fours industriels. La composition du combustible et la température des parois de la chambre de combustion sont deux paramètres très influents de ce régime. Dans de précédents travaux menés au CORIA, l’étude du régime de combustion sans flamme des mélanges méthane-hydrogène à 18% d’excès d’air a mené à des résultats originaux et prometteurs. D’autre part, la haute température des parois s’est avérée un élément primordial pour la stabilisation de la combustion sans flamme. Dans le cadre du projet CANOE en collaboration avec GDF SUEZ et l’ADEME, cette thèse a pour objectif, d’une part de compléter l’étude de l’extension de ce régime à des mélanges méthane-hydrogène pour des conditions opératoires plus proches des conditions classiques de fonctionnement de brûleurs (10% d’excès d’air), et d’autre part, d'étudier les problèmes de stabilité de la combustion sans flamme en environnement à basse température pour envisager son application à des configurations de type chaudière industrielle.Sur le four pilote à hautes températures de parois du CORIA, l’ajout de l’hydrogène dans le combustible a permis de garder le régime de combustion sans flamme pour toutes les proportions méthane - hydrogène avec très peu d’émissions polluantes. Une augmentation de l’excès d’air est toutefois nécessaire pour certaines conditions opératoires. Les expériences réalisées avec abaissement progressif de la température des parois ont permis d’étudier l’influence de celle-ci sur le développement de la combustion sans flamme, et d’atteindre les limites de stabilité de ce régime. Des résultats similaires sont obtenus sur une installation semi-industrielle de GDF SUEZ. L’ajout d’hydrogène rend la combustion sans flamme moins sensible à l’abaissement de la température de parois. Une étude analytique de jets turbulents confinés a été développée pour représenter l'interaction entre les jets de réactifs et leur environnement dans la chambre de combustion permettant d'atteindre le régime de combustion sans flamme par entraînement, dilution et préchauffage. Ce modèle nous a permis d’établir une étude systématique permettant de mettre en valeur l’effet de chaque paramètre sur le développement des jets dans l’enceinte, et ainsi servir de moyen de pré-dimensionnement de brûleur à combustion sans flamme. L'apport de chaleur nécessaire à la stabilisation à basse température a ainsi été estimé. Sur cette base, un brûleur adapté aux configurations à parois froides a été dimensionné et fabriqué. L’applicabilité de la combustion sans flamme avec ce brûleur dans une chambre de combustion à parois froides, spécialement conçue et fabriquée dans cet objectif au cours de cette thèse, a été étudiée. Un régime de combustion diluée à basses températures a pu être stabilisé, mais le fort taux d'imbrûlés produits en sortie reste à réduire. / Mild flameless combustion is a massively diluted combustion regime associating high energy efficiency and very low pollutant emissions from industrial furnaces. The fuel composition and walls temperature are two very influential parameters of this combustion regime. In previous works realized at CORIA, flameless combustion of methane - hydrogen mixtures at 18% of excess air has shown very promising results. In another hand, high walls temperature is an essential element for flameless combustion stabilization. Within the framework of the project CANOE in collaboration with GDF SUEZ and ADEME, the objective of this PhD thesis is to complete the study of flameless combustion for methane-hydrogen mixtures in operating conditions similar to classical operating conditions of burners (10% of excess air), and in another hand, to study the stability limits of this combustion regime in low temperature environment like in industrial boiler.Experiments realized on the CORIA high temperature pilot facility, have proved that hydrogen addition in the fuel keep flameless combustion regime stable for all methane - hydrogen proportions, with very ultra-low pollutant emissions. An increase of excess air is however necessary for some operating conditions.Experiments realized with wall temperature progressive decrease allowed to study the influence of this parameter on flameless combustion, and to reach its stability limits. Similar results are obtained on the semi-industrial facility of GDF SUEZ. With hydrogen addition, flameless combustion is less sensitive to wall temperature decrease. An analytical representation of confined turbulent jets has been then developed to represent interaction between the reactant jets and their environment in the combustion chamber allowing reaching fameless combustion regime by entrainment, dilution and preheating. The effect of each parameter on the development of the jets can be then studied, which can be used as convenient tool of flameless combustion burners design. The heat quantity necessary for the low wall temperature stabilization has been quantified. On this base, a burner adapted to the configurations with cold walls has been designed. The applicability of the flameless combustion with this burner has been studied in a combustion chamber with low wall temperature specially designed for this purpose during this thesis. A mild diluted combustion regime has been achieved, but the high levels of unburnt gases have to be reduced.

Les collisions d’ions lourds à haute énergieproduisentunnouvelétatdelamatièreappelé le plasma de quarks et de gluons. Un parton traversant le plasma perds de l’énergie, en atténuant les gerbeshadroniques:c’estl’effetde"jetquenching". La dépendance du jet quenching dans la saveur du parton fournit des contraintes sur les modèles de perte d’énergie. Le déséquilibre d’une paire de jets issus de quarks b est une observable appropriée pour étudier ce phénomène. Cette thèse présente lamesure du déséquilibre en impulsion transverse des jets de b et des jets inclusifs (non-identifiés), dans des collisions PbPb a √sNN = 5.02 TeV, réalisée avecledétecteurCMSauLHCpouruneluminosité intégrée de 404 µb−1. Aucune différence n’est observée dans le jet quenching entre les jets issus de partons légers et lourds. Une analyse des résultats à l’aide d’un modèle simple de perte d’énergie est présentée. / The collisions of heavy ions at high energy produce the new state of matter called the quark gluon plasma. A parton traversing the plasma loses its energy which results in the jet quenching phenomenon. The dependence of the jet quenchingonthepartonflavorprovidesconstraints the models describing energy loss. The imbalance of b-jets is a very suitable observable to study this phenomena. This dissertation presents the measurement of the transverse momentum imbalance of b-jets and inclusive (non-identified) jets in PbPb collisions at √sNN = 5.02 TeV which is performed with the CMS detector at the LHC with total integral luminosity of 404 µb−1. No significant difference in jet quenching between light and heavy flavor jets is observed. The interpretation of results with a simple model of energy loss is performed.

No description available.