Ces travaux de doctorat portent sur la réduction du bruit d'origine aérodynamique émis par les ventilateurs et les doublets d'hélices contra-rotatifs. La méthodologie proposée consiste à intégrer des méthodes rapides et précises de prédiction des niveaux sonores dans le processus de conception. Cette thématique a vu son intérêt augmenter depuis que l'Union Européenne a restreint les limites d'exposition au bruit en milieu de travail et dans les zones habitées à proximité des aéroports. Parmi les méthodes numériques employées en aéroacoustique, les méthodes hybrides de prédiction du bruit sont considérées comme particulièrement appropriées pour la conception automatisée du fait de leur coût modéré en temps de calcul. Ces méthodes séparent la résolution de l'écoulement aérodynamique de celle de la génération du bruit et de sa propagation en champ lointain. L'écoulement aérodynamique est obtenu par simulation numérique, tandis que l'acoustique est traitée par méthodes analytiques. Ces méthodes analytiques développées et validées pour déterminer le bruit d'un profil aérodynamique placé dans un écoulement turbulent seront étendues pour traiter le réponse acoustique de pales en rotation. Ces travaux se concentrent sur deux configurations de ventilateurs basses vitesses. La première configuration traitée est le doublet d'hélices contra-rotatif de 4.2m de diamètre de la soufflerie L-1 de l'Institut von Karman (VKI). Ce système permet d'étudier le phénomène de bruit tonal et à large bande dû à l'impact des sillages turbulents, générés par l'hélice amont, sur l'hélice aval. La deuxième configuration traitée est un ventilateur à quatre pales du CETIAT (France) installé seul dans un large plenum. Ce système permet d'étudier le bruit propre ou bruit de bord de fuite causé par l'interaction des tourbillons générés par l'écoulement autour de la pale avec le bord de fuite de la pale. Pour cette configuration, des données expérimentales sont rendues disponibles dans le cadre d'un projet commun entre le VKI et le CETIAT. Les méthodes hybrides sont développées et mises en oeuvre pour ces deux mécanismes de bruit présents dans les deux configurations de ventilateur. L'objectif de ces travaux de thèse est d'employer les méthodes hybrides ainsi calibrées et validées pour réaliser l'optimisation du doublet d'hélices contra-rotatif de la soufflerie L-1. Le coeur de ces travaux portera sur l'extension des méthodes hybrides pour la prédiction du bruit d'un profil dans un écoulement turbulent uniforme au cas du bruit tonal et à large bande d'interaction de sillages et du bruit à large bande de bord de fuite dans des ventilateurs basses vitesses. Il sera montré qu'il est possible de déterminer le spectre de bruit de manière rapide et précise en s'appuyant sur la connaissance du champ aérodynamique dont les quantités seront extraites de simulations numériques stationnaires (RANS) pour alimenter la formulation analytique retenue. Cette dernière doit être adaptée au mécanisme de bruit étudié, à savoir l'interaction d'une pale de ventilateur avec un sillage ou celle du bord de fuite avec la turbulence qui s'est développé le long de la pale. Les deux mécanismes de bruit sont d'abord modélisés avec des fonctions analytiques qui sont calibrés avec les données des simulations numériques. Les modèles de sources de bruit ainsi que les estimations finales de spectre de bruit sont comparées aux données expérimentales disponibles et à des simulations directes. Enfin la méthodologie retenue est mise en oeuvre dans le cadre de l'optimisation du doublet d'hélices L-1 au moyen d'un algorithme génétique. L'étude détaillée de la sensibilité des paramètres et des contraintes de l'optimisation apporte un nouveau regard sur l'optimisation multi-objectif efficacité-bruit qui sera de plus en plus utilisée pour la conception de turbomachine dans le futur. / Abstract : The context of this thesis is the reduction of noise emitted by ventilation fans and aeronautical counter-rotating open rotors, which will be achieved by implementing fast and accurate noise prediction methods in the design process. The interest towards this subject has increased since the European Union enforced lower limits of exposure to noise in work environments and also to environmental noise in the proximity of airports. In the field of computational aeroacoustics, hybrid methods for noise prediction are considered particularly suitable for use in an automated design procedure due to their low computational cost. In fact they split the description of the flow field, which is made by computational fluid dynamics, from the quantification of the source of noise and of its propagation, obtained by using analytic formulations. Such analytic methods have already been used successfully for the prediction of the noise emitted by an airfoil placed in a turbulent flow; it is therefore natural to try to extend their applicability to the case of rotating blades. Two application cases have been chosen for this thesis. The first one is the 4.2 m diameter counter-rotating fan of the von Karman Institute (VKI) L1 low-speed wind tunnel, which is used to study the phenomenon of wake-interaction tonal and broadband noise. The second application case is a four-bladed low-speed ventilation fan in which the dominant source of noise is the trailing-edge or self-noise caused by the turbulent eddies passing over the trailing-edge of the blade. In this case, an experimental database has been made available by CETIAT, France, in the framework of a collaborative project with VKI. The final step of the project will be to use the prediction codes developed for both the noise phenomena in the geometric optimization of the L1 counter-rotating fan. The fundamental question that will be addressed in the thesis is how to extend the hybrid CFD-analytic methods to predict noise from an airfoil in a uniform turbulent flow to the case of tonal and broadband wake-interaction noise and trailing-edge broadband noise in low-speed fans. It will be shown that it is possible to provide a fast and reasonably accurate prediction of the spectrum of noise emitted by low-speed fans by extracting flow data from Reynolds Averaged Navier-Stokes (RANS) simulations and using them as input to Amiet's analytic formulation, provided that this has been carefully adapted to the studied noise generation phenomenon, i.e. the interaction of the leading-edge of a fan blade with an incoming wake or of the trailing-edge with the turbulent boundary layer over the blade surface. Concerning the methodology, both noise generation mechanisms will first be modeled with analytic functions, then the necessary flow field input will be extracted from RANS simulations and the models will be validated with respect to experimental data, whenever possible, or to higher fidelity simulations. The last step of the project is the application of these noise prediction methods to the shape optimization of the L-1 fan blades by means of a genetic algorithm. The sensitivity analysis of the design parameters and of the constraints used in the optimization process provides a new perspective on the multi-objective efficiency-noise optimization approach which will be increasingly used in turbomachinery design in the future.

The standard model of particle physics is the most precisely verified scientific theory in the history of mankind. However, extended theories are already in place, ready to supersede the standard model should it fail to describe any new physics that may be observed in the next generation of high energy particle accelerators. One such minimal extension is the Two Higgs Doublet Model (2HDM). However, the appearance of additional symmetries to those of the gauge symmetries in the 2HDM can have consequences for the cosmological viability of the model, with the possibility for non-trivial topological defects forming during spontaneous symmetry breaking phase transitions.In this research we perform a systematic study of six accidental Higgs Family and CP symmetries that can occur in the 2HDM potential, by introducing and utilizing our Majorana scalar-field formalism. General sufficient conditions for convexity and stability of the scalar potential are derived and analytical solutions for two non-zero neutral vacuum expectation values of the Higgs doublets for each of the six symmetries are presented, in terms of the parameters of the theory. We identify the topological defects associated with the spontaneous symmetry breaking of each symmetry by means of a homotopy-group analysis. We find the existence of domain walls from the breaking of Z2, CP1 and CP2 discrete symmetries, vortices in models with broken U(1)PQ and CP3 symmetries and a global monopole in the SO(3)HF-broken model. We study the associated topological defect solutions as functions of the potential parameters via gradient flow methods. We also consider the cosmological implications of the topological defects and are able to derive bounds on physical observables of the theory in order to avoid contradictions with the theoretical limits on topological defects. The application of our Majorana scalar-field formalism in studying more general scalar potentials that are not constrained by the U(1)Y hypercharge symmetry is discussed. In particular, the formalism may be used to properly identify seven previously hidden symmetries that may be manifest in a U(1)Y invariant scalar potential for particular choices of the model parameters.

No description available.

No description available.

Utilisée depuis des milliers d’années sous ses manifestations naturelles par l’Homme, cette ressource fait l’objet d’une exploitation commerciale depuis seulement le XXe siècle, à destination du chauffage de bâtiments, de certains usages industriels ainsi que de la production d’électricité. La France compte parmi les pionniers concernant l’usage direct de la chaleur alors qu’aucune filière industrielle n’est véritablement effective pour la production d’électricité d’origine géothermique. Le projet sélectionné, intitulé FONGEOSEC, a pour objectif la conception et la réalisation d’un démonstrateur innovant préindustriel d’une centrale géothermique haute enthalpie exploité par cogénération d’électricité et de chaleur. Un travail de recherche et développement, conduit par un consortium composé de partenaires industriels et scientifiques, vise au lancement de la filière industrielle géothermique haute température en France. L’objectif général des travaux de thèse porte sur une meilleure compréhension globale des comportements hydrauliques, massiques et thermiques des formations profondes en réponse à une sollicitation anthropique de longue durée. Il s’agit d’identifier les paramètres clés régissant la réponse du complexe réservoir à la suite d’une exploitation géothermique. Un point particulier sera consacré à caractériser la part de chacun des modes de transport de chaleur en milieu poreux – conduction thermique, convection libre et forcée – dans l’établissement des performances thermiques de l’ouvrage considéré. Plusieurs dispositifs techniques d’exploitation seront proposés afin de réduire les incertitudes associées au système géothermique souterrain et garantir le succès du projet FONGEOSEC. L’impact des mécanismes thermo-convectifs au voisinage des forages d’exploitation géothermique de grande profondeur reste peu documenté, a fortiori dans le cas de dispositifs déviés adoptant une complétion particulière. L’outil retenu pour l’évaluation des performances du dispositif au contact de l’encaissant est la modélisation numérique distribuée. La variabilité des propriétés physiques de l’hydrosystème, de la conception et des modalités d’exploitation du dispositif sur le comportement hydraulique et thermique de l’exploitation est envisagée selon différentes approches développées à partir de modèles numériques 3D. / Used for thousands of years under its natural manifestations, this resource has been commercially exploited since the twentieth century, for the heating of buildings, certain industrial uses and the production of electricity. France is one of the pioneers in the direct use of heat, whereas no industrial cluster is truly effective for the production of geothermal electricity. The selected project, FONGEOSEC, aims to design and produce an innovative pre-industrial demonstrator of a high enthalpy geothermal power plant operated by cogeneration of electricity and heat. A research and development project, led by a consortium of industrial and scientific partners, aims to launch the high-temperature geothermal industrial sector in France. The general objective of this thesis is to improve the understanding of the hydraulic, mass and thermal behavior of deep porous formations in response to long-term anthropogenic stress. The aim is to identify the key parameters governing the response of the reservoir complex related to geothermal operation. A particular point will be devoted to characterize the part of each mode of transport of heat in porous medium – thermal conduction, free and forced convection – in the establishment of the thermal performances of the geothermal power plant. Several technical operating devices will be proposed to reduce the uncertainties associated with the underground geothermal system and guarantee the success of the FONGEOSEC project. The impact of thermo-convective mechanisms in the vicinity of deep geothermal borehole remains poorly documented, especially in the case of deviated wells with a complex inner geometry. The evaluation of the hydraulic and thermal performances of the device, based on 3D numerical modeling, is conducted according to different approaches.

La découverte au LHC d'un boson scalaire possédant des propriétés fortement similaires à celles du boson de Higgs du Modèle Standard, indique certainement que l'acteur principal du mécanisme de la brisure de symétrie électrofaible a été trouvé. Cependant, plusieurs théories au-delà du Modèle Standard prédisent l'existence d'une particule similaire provenant d'un secteur plus riche. La mesure des propriétés du boson scalaire découvert nous permettra de savoir si celui-ci correspond ou non à la particule prédite par le Modèle Standard. Pour ce faire, nous utilisons une approche modèle-indépendante via le cadre d'une théorie des champs effective (TCE) pour le boson de Higgs, afin de paramétrer les déviations de ses couplages à la matière par rapport au Modèle Standard. Nous nous focalisons sur une théorie basée sur un Lagrangien effectif de dimension 6, qui inclut à la fois des opérateurs de Charge-Parité paire et impaire. Dans un premier temps nous tentons d'obtenir des contraintes sur une partie des coefficients effectifs de Wilson, pertinents pour la physique du boson de Higgs au LHC, en utilisant les dernières données de taux du Higgs provenant du Run-I des expériences ATLAS et CMS, ainsi que des données de précision électrofaibles du LEP, SLC et du Tevatron. Nous montrons que les données actuelles sont capables de contraindre de manière significative les opérateurs de CP paire ainsi que certains opérateurs de CP impaire du Lagrangien effectif. Dans un second temps nous étudions de possibles désintégrations exotiques du boson de Higgs, qui ne sont générées qu'en tant que conséquence des opérateurs effectifs de dimension 6 (générés par de la nouvelle physique inconnue) et non par le Modèle Standard seul. Les limites expérimentales actuelles nous permettent de placer des bornes supérieures sur ces opérateurs. Pour finir nous analysons certaines limitations de l'approche effective, par la comparaison de certains processus avec boson de Higgs à l'ordre des arbres dans la TCE, avec les prédictions pour les mêmes processus calculés à l'arbre et à une boucle, dans une classe simple d'extensions du Modèle Standard connue sous le nom de "Two-Higgs doublet models". / The discovery at the LHC of a scalar boson, the properties of which are strongly similar to the ones of the Standard Model Higgs boson, certainly indicate that the main actor of the electroweak symmetry breaking mechanism was found. However, many beyond-the-Standard Model theories predict the existence of such a similar particle coming from a richer sector. Measuring the properties of the discovered scalar will tell us whether or not it is the same particle as the one predicted by the Standard Model. To this aim we use a model-independent approach through a Higgs Effective Field Theory (EFT) framework to parametrize the deviations of its couplings to matter from the Standard Model. We focus on a Higgs EFT framework based on a dimension-6 effective Lagrangian, including both CP-even and CP-odd operators. We first attempt at putting constraints on a part of the effective Wilson coefficients relevant for Higgs physics at the LHC, using the latest Higgs rates data from the Run-I of the ATLAS and CMS experiments, as well as electroweak precision data from LEP, SLC and Tevatron. We show that the current data is able to significantly constrain CP-even and some CP-odd operators of the effective Lagrangian. We then move on to the study of possible exotic Higgs decays, that can only be generated as a consequence of the effective dimension-6 operators (generated from unknown new physics) and not from within the Standard Model alone, and derive upper bounds on those operators given the present experimental limits. Finally we analyze some of the limitations of the effective approach by comparing predictions on some Higgs processes at tree-level in EFT with respect to predictions at tree and 1-loop level on the same processes computed in a simple class of Standard Model extensions known as "Two-Higgs doublet models".

Flutter is one of the primary aeroelastic phenomena that must be considered in aircraft design. Flutter is a self-sustaining structural vibration in which energy is extracted from the air flow and transferred to the structure. The amplitude of the vibration grows exponentially until structural failure occurs. Flutter stability requirements often influence the design of an aircraft, making accurate flutter prediction capabilities an essential part of the design process. Advances in computational fluid dynamics and computational power make it possible to solve the fluid flow and structural dynamics simultaneously, providing highly accurate solutions especially in the transonic flow regime. This procedure is, however, too time-consuming to be used in the design optimisation process. As a result panel codes, e.g., the doublet lattice method, and modal-based structural analysis methods are still being used extensively and continually improved. One application that is lagging in terms of accuracy and simplicity (from the user’s perspective) is the flutter analysis of T-tails. The flutter analysis of a T-tail usually involves the calculation of additional aerodynamic loads, apart from the loads calculated by the standard unsteady aerodynamic codes for conventional empennages. The popular implementations of the doublet lattice method do not calculate loads due to the in-plane motion (i.e., lateral or longitudinal motion) of the horizontal stabiliser or the in-plane loads on the stabiliser. In addition, these loads are dependent on the steady-state load distribution on the stabiliser, which is ignored in the doublet lattice method. The objective of the study was to extend the doublet lattice method to calculate the additional aerodynamic loads that are crucial for T-tail flutter analysis along with the customary unsteady air loads for conventional configurations. This was achieved by employing the Kutta-Joukowski theorem in the calculation of unsteady air loads on lifting surface panels. Calculating the additional unsteady air loads for T-tails within the doublet lattice method significantly reduces the human effort required for T-tail flutter analysis as well as the opportunities for introducing errors into the analysis. During the course of the study it became apparent that it was necessary to consider the quadratic mode shape components in addition to the linear mode shape components. Otherwise the unsteady loads due to the rotation (“tilting”) of the steady-state load on the stabiliser, one of the additional aerodynamic loads that are crucial for T-tail flutter analysis, would give rise to spurious generalised forces. In order to reduce the additional burden of determining the quadratic mode shape components, methods for calculating quadratic mode shape components using linear finite element analysis or estimating them from the linear mode shape components were developed. Wind tunnel tests were performed to validate the proposed computational method. A T-tail flutter model which incorporated a mechanism for changing the incidence angle of the horizontal stabiliser, and consequently the steady-state load distribution on the horizontal stabiliser, was used. The flutter speed of this model as a function of the horizontal stabiliser incidence was determined experimentally and compared to predictions. Satisfactory correlation was found between predicted and experimentally determined flutter speeds. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012

Flutter is one of the primary aeroelastic phenomena that must be considered in aircraft design. Flutter is a self-sustaining structural vibration in which energy is extracted from the air flow and transferred to the structure. The amplitude of the vibration grows exponentially until structural failure occurs. Flutter stability requirements often influence the design of an aircraft, making accurate flutter prediction capabilities an essential part of the design process. Advances in computational fluid dynamics and computational power make it possible to solve the fluid flow and structural dynamics simultaneously, providing highly accurate solutions especially in the transonic flow regime. This procedure is, however, too time-consuming to be used in the design optimisation process. As a result panel codes, e.g., the doublet lattice method, and modal-based structural analysis methods are still being used extensively and continually improved. One application that is lagging in terms of accuracy and simplicity (from the user’s perspective) is the flutter analysis of T-tails. The flutter analysis of a T-tail usually involves the calculation of additional aerodynamic loads, apart from the loads calculated by the standard unsteady aerodynamic codes for conventional empennages. The popular implementations of the doublet lattice method do not calculate loads due to the in-plane motion (i.e., lateral or longitudinal motion) of the horizontal stabiliser or the in-plane loads on the stabiliser. In addition, these loads are dependent on the steady-state load distribution on the stabiliser, which is ignored in the doublet lattice method. The objective of the study was to extend the doublet lattice method to calculate the additional aerodynamic loads that are crucial for T-tail flutter analysis along with the customary unsteady air loads for conventional configurations. This was achieved by employing the Kutta-Joukowski theorem in the calculation of unsteady air loads on lifting surface panels. Calculating the additional unsteady air loads for T-tails within the doublet lattice method significantly reduces the human effort required for T-tail flutter analysis as well as the opportunities for introducing errors into the analysis. During the course of the study it became apparent that it was necessary to consider the quadratic mode shape components in addition to the linear mode shape components. Otherwise the unsteady loads due to the rotation (“tilting”) of the steady-state load on the stabiliser, one of the additional aerodynamic loads that are crucial for T-tail flutter analysis, would give rise to spurious generalised forces. In order to reduce the additional burden of determining the quadratic mode shape components, methods for calculating quadratic mode shape components using linear finite element analysis or estimating them from the linear mode shape components were developed. Wind tunnel tests were performed to validate the proposed computational method. A T-tail flutter model which incorporated a mechanism for changing the incidence angle of the horizontal stabiliser, and consequently the steady-state load distribution on the horizontal stabiliser, was used. The flutter speed of this model as a function of the horizontal stabiliser incidence was determined experimentally and compared to predictions. Satisfactory correlation was found between predicted and experimentally determined flutter speeds. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012

It is widely believed that the Standard Model (SM) can not be a fundamental theory of the basic interactions. Originated from this fact, many new physics models have been proposed. Among them, the two Higgs doublet model (2HDM), the SM enlarged by adding one extra scalar doublet, is considered as the simplest extension of the SM. In this work, within the framework of the model III version of the 2HDM, the exclusive decay the branching ratio is calculated and discussed in various physical regions determined by model parameters. It is observed that it is possible to reach present experimental upper limits in model Finally, the avor changing top quark decay,

Submitted by VIVIAN VENTURA FERREIRA LUIZ (vivisventura@gmail.com) on 2018-06-14T17:51:35Z No. of bitstreams: 1 dissertacao.pdf: 1531949 bytes, checksum: 577b1199d5fc233ab7cc7e672975849a (MD5) / Approved for entry into archive by Hellen Sayuri Sato null (hellen@ift.unesp.br) on 2018-06-15T17:55:01Z (GMT) No. of bitstreams: 1 luiz_vvf_me_ift.pdf: 1531949 bytes, checksum: 577b1199d5fc233ab7cc7e672975849a (MD5) / Made available in DSpace on 2018-06-15T17:55:01Z (GMT). No. of bitstreams: 1 luiz_vvf_me_ift.pdf: 1531949 bytes, checksum: 577b1199d5fc233ab7cc7e672975849a (MD5) Previous issue date: 2017-09-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O problema da matéria escura é uma das questões abertas da cosmologia e da física de partículas. Inúmeras observações, em diferentes escalas astronômicas, sustentam que a quantidade de matéria luminosa presente não é capaz de explicar o comportamento observado. A solução para esta inconsistência foi obtida através da introdução de uma nova forma de matéria que, não interagindo com a luz, foi intitulada por matéria escura. O Modelo Padrão da Cosmologia indica que esta componente contribui com mais de 80% da densidade de matéria no Universo, deve ser estável, não relativística e sua densidade relíquia deve combinar com as medidas obtidas pelas flutuações da CMB. Apesar disso, a natureza da matéria escura ainda é um mistério. Entre as partículas candidatas à matéria escura os mais populares são os chamados WIMPs. Esta espécie é considerada uma relíquia térmica e podem fornecer uma abundância compatível com a observada. Nesta direção, o presente trabalho então, trata uma extensão do Modelo Padrão da Física de Partículas, uma vez que este modelo não fornece nenhuma partícula apropriada à matéria escura, chamada Modelo do Dubleto Inerte, que é obtido adicionando um novo dubleto escalar por meio de uma simetria Z_2 que desenvolve uma configuração de vácuo trivial. Dentro do novo espectro de partículas estudamos aquela que parece propor um candidato viável à matéria escura. / The problem of dark matter is one of the open questions of cosmology and particle physics. Several observations, at different astronomical scales, maintain that the amount of light matter present is not able to explain the observed behavior. The solution to this inconsistency was obtained by introducing a new form of matter which, not interacting with light, was titled as dark matter. The Standard Model of Cosmology indicates that this component contributes with more than 80% of the matter density in the Universe, must be stable, non relativistic and its relic density should match with the measurements obtained by the fluctuations of the CMB. Despite this, the nature of dark matter is still a mystery. Among the candidate particles for dark matter the most popular are the so-called WIMPs. This species is considered a thermal relic and can provide an abundance compatible with that observed. In this direction, the present work then deals with an extension of the Standard Model of Particle Physics, since this model does not provide any particle appropriate to dark matter, called Inert Doublet Model, which is obtained by adding a new scalar doublet through a Z_2 symmetry that develops a trivial vacuum configuration. Inside this new spectrum of particles we study the one that seems to propose a viable candidate to the dark matter.