An analytical dispersion model has been derived to determine the distribution of velocities and concentrations of a tracer in a two-dimensional jet in a coflowing ambient fluid. The particular novelty of this model is that it bridges the gap between near-field (where initial momentum dominates behaviour) and far-field (where ambient turbulence is more important) domains. We describe this domain as the ???intermediate field???. In a literature review of coflowing jets we find several laboratory studies and models which can predict the velocities (and in some cases concentrations) in a 2D jet, however they all have shortcomings. None could fully account for ambient turbulence, and all were strictly near-field, i.e. they are unable to describe behaviour when ambient turbulence dominates the initial shear. A brief review of analytical far-field models was also undertaken. There are standard solutions for the dispersion of a 2D continuous source but none that allow for an initial source momentum or non-uniform velocity. As opposed to the near-field coflow approach used by other researchers we start from the far-field, modifying the simple diffusion models by perturbing the governing equations to allow for the initial momentum. Models are developed for both along-stream velocity and the concentration field of a tracer. From the velocity model, a comparison is made with experimental data available from one researcher (Wang, 1996) and an existing near-field coflow model PJCMERG (Davidson, 1989). The initial conditions (width and excess velocity) for our model are determined by Gaussian curve fitting to an arbitrary point in the near-field. The diffusivity parameter is used to adjust (tune) the model until the centreline velocity profile matches. We can always achieve this match and to a much closer degree than PJCMERG. There are no available laboratory or field data for concentrations of a tracer in a 2D coflowing jet although the near-field model PJCMERG does have a tracer component. We demonstrate how PJCMERG cannot converge to any far-field model, while our model provides a neat transition between the near-field and far-field. We have started the extension of the 2D model to the more common 3D situation although we have yet to carry out any comparisons with other models or data. The model development is included in an appendix for other researchers to pick up.

An analytical dispersion model has been derived to determine the distribution of velocities and concentrations of a tracer in a two-dimensional jet in a coflowing ambient fluid. The particular novelty of this model is that it bridges the gap between near-field (where initial momentum dominates behaviour) and far-field (where ambient turbulence is more important) domains. We describe this domain as the ???intermediate field???. In a literature review of coflowing jets we find several laboratory studies and models which can predict the velocities (and in some cases concentrations) in a 2D jet, however they all have shortcomings. None could fully account for ambient turbulence, and all were strictly near-field, i.e. they are unable to describe behaviour when ambient turbulence dominates the initial shear. A brief review of analytical far-field models was also undertaken. There are standard solutions for the dispersion of a 2D continuous source but none that allow for an initial source momentum or non-uniform velocity. As opposed to the near-field coflow approach used by other researchers we start from the far-field, modifying the simple diffusion models by perturbing the governing equations to allow for the initial momentum. Models are developed for both along-stream velocity and the concentration field of a tracer. From the velocity model, a comparison is made with experimental data available from one researcher (Wang, 1996) and an existing near-field coflow model PJCMERG (Davidson, 1989). The initial conditions (width and excess velocity) for our model are determined by Gaussian curve fitting to an arbitrary point in the near-field. The diffusivity parameter is used to adjust (tune) the model until the centreline velocity profile matches. We can always achieve this match and to a much closer degree than PJCMERG. There are no available laboratory or field data for concentrations of a tracer in a 2D coflowing jet although the near-field model PJCMERG does have a tracer component. We demonstrate how PJCMERG cannot converge to any far-field model, while our model provides a neat transition between the near-field and far-field. We have started the extension of the 2D model to the more common 3D situation although we have yet to carry out any comparisons with other models or data. The model development is included in an appendix for other researchers to pick up.

The operation speed of power delivery system of packages has been upgraded to GHz. The instant current will pass to the power plane of the mother board by way of the IC pins and result in electromagnetic wave propagation between the power plane and the ground plane, then to produce the programs of electromagnetic interference. In this thesis, we will analyze the EMI of power delivery system of packages by finite-difference time-domain in two dimensions structure in three sections. In firist section, to computing EMI in finite-difference time-domain in two dimensions structure. In second section, to analyze more complicated power delivery plane, ex: EBG, in finite-difference time-domain in two dimensions structure. In three section, to add property of capacitors on power plane to reduce EMI in two dimensions structure. Above all, we hope to built a fast computing method to compute EMI to solve the time-consuming problems of full-wave simulated software. And to supply the engineer to deal with the similar problems in packages efficiently.

Measuring the farfield noise levels of full-scale rotor systems is not trivial and can be costly. Researchers prefer to perform small-scale experiments in the laboratory so that they can extrapolate the model scaled results to the larger scale. Typically Inverse Square Law (ISL) is used to extrapolate the sound pressure levels (SPL), obtained from model-scale experiments at relatively small distances to predict noise at much larger distances for larger scale systems. The assumption underlying this extrapolation is that the source itself can be treated as a point sound source. At what distance from a rotor system it can be treated as a point source has never been established. Likewise, many theoretical models of shielding by hard surfaces assume the source to be a point monopole source. If one is interested in shielding the noise of a rotor system by interposing a hard surface between the rotor and the observer, can the rotor system really be considered to be a monopole? If rotating noise sources are under consideration what is the effect of configuration and design parameters? Exploring the validity of point source assumption alluded to above for a rotor for farfield acoustic measurements with and without shielding form the backbone of the present work.

This thesis proposes to predict the sound emitted from low-speed fans and its scattered-field by installation effects related to industrial applications. Both tonal and broadband components of fan noise are investigated. Methods existing in the literature contain assumptions and simplifications in order to deal with fan noise problems in analytical manner, such as consideration of an observer located in the far-field of the source. Firstly, the effect of far-field assumption in the tonal fan noise formulation is addressed. Using artificial blade sources, a comparison between two closed-form analytical solutions and a numerical technique is performed for validation in free-field. Secondly, the scattered field of the tonal fan noise is investigated using numerical and analytical techniques. The acoustic field of a rotor operating in a finite duct is first investigated combining the closed-form analytical formulations with the Boundary Element Method (BEM). Since BEM would be computationally demanding for high frequency applications, analytical scattering techniques are also introduced. Reflection and scattering of sound waves by a large plane are first addressed replacing the plane with an image source. Secondly, an exact analytical solution considering scattering of the tonal fan noise by a rigid corner is derived. Another point addressed in this thesis is the prediction of the broadband noise generated by a low-speed axial fan operating in turbulent stream. Amiet's theory of turbulence-interaction noise for a stationary air foil is considered. One of the key points proposed in this thesis is an extension of Amiet's method, allowing prediction of the acoustic field of the airfoil in its geometrical near-field in a semi-analytical perspective. The extended formulation is compared with Amiet's classical solution and a reference solution obtained with numerical integration involving no geometrical far-field assumption. Experiments are also performed in anechoic chamber using an isolated airfoil located in grid generated turbulence. Another assumption made in Amiet's theory is the consideration of uniform flow impinging onto the airfoil. However this assumption is not valid for most industrial applications. Different methods exist in literature to deal with this problem. A new approach is proposed in order to take the span wise varying flow conditions into account. Including all the improvements, the broadband acoustic responses of a stationary airfoil located in the developing region of a jet and of a low-speed axial fan operating in a turbulent stream are investigated and validated against measurements. Finally, scattering of the sound generated by the considered airfoil and fan by benchmark obstacles is addressed numerically and analytically. Since BEM is not capable to handle statistical source fields directly, an innovative approach obtained by re-formulating the deterministic BEM method is employed. The final model is compared to the numerical, analytical and experimental solutions for validation purposes.

An analytical dispersion model has been derived to determine the distribution of velocities and concentrations of a tracer in a two-dimensional jet in a coflowing ambient fluid. The particular novelty of this model is that it bridges the gap between near-field (where initial momentum dominates behaviour) and far-field (where ambient turbulence is more important) domains. We describe this domain as the ???intermediate field???. In a literature review of coflowing jets we find several laboratory studies and models which can predict the velocities (and in some cases concentrations) in a 2D jet, however they all have shortcomings. None could fully account for ambient turbulence, and all were strictly near-field, i.e. they are unable to describe behaviour when ambient turbulence dominates the initial shear. A brief review of analytical far-field models was also undertaken. There are standard solutions for the dispersion of a 2D continuous source but none that allow for an initial source momentum or non-uniform velocity. As opposed to the near-field coflow approach used by other researchers we start from the far-field, modifying the simple diffusion models by perturbing the governing equations to allow for the initial momentum. Models are developed for both along-stream velocity and the concentration field of a tracer. From the velocity model, a comparison is made with experimental data available from one researcher (Wang, 1996) and an existing near-field coflow model PJCMERG (Davidson, 1989). The initial conditions (width and excess velocity) for our model are determined by Gaussian curve fitting to an arbitrary point in the near-field. The diffusivity parameter is used to adjust (tune) the model until the centreline velocity profile matches. We can always achieve this match and to a much closer degree than PJCMERG. There are no available laboratory or field data for concentrations of a tracer in a 2D coflowing jet although the near-field model PJCMERG does have a tracer component. We demonstrate how PJCMERG cannot converge to any far-field model, while our model provides a neat transition between the near-field and far-field. We have started the extension of the 2D model to the more common 3D situation although we have yet to carry out any comparisons with other models or data. The model development is included in an appendix for other researchers to pick up.

Dans cette thèse, une formulation pour l’extraction du couple « champ lointain » d’un rotor d’hélicoptère en vol stationnaire est présentée. Cette formulation est dérivée de la méthode d’extraction de la traînée « champ lointain » d’un avion, basée sur les travaux de van der Vooren et Destarac [?, ?, ?]. Un outil développé à l’Onera à partir de cette théorie permet de donner une analyse complète de la traînée aérodynamique d’un avion. Il est basé sur l’analyse physique et locale de l’écoulement calculé autour de l’aéronef, et décompose la traînée totale, aussi appelée traînée mécanique, en composantes physiques. Ces composantes physiques peuvent être définies comme suit : 1) la traînée d’onde, 2) la traînée visqueuse, 3) la traînée induite. L’adaptation de la méthode d’extraction de la traînée d’un avion à un rotor en vol stationnaire nécessite l’utilisation du couple rotor à la place de la traînée de l’avion, ce qui donne la décomposition suivante : 1) le couple d’onde, 2) le couple visqueux, 3) le couple induit. Les simulations de rotor diffèrent de celles de l’avion dans la mesure où les équations d’Euler (ou RANS) ne sont pas écrites dans le même repère de référence : les simulations d’avion utilisent généralement une formulation en vitesse relative tandis que les simulations d’un rotor d’hélicoptère utilisent la vitesse absolue projetée dans le repère relatif. Cette différence conduit à deux formulations différentes des équations de l’écoulement, et nécessairement deux formulations différentes de l’extraction de la traînée ou du couple. Ce changement de repère implique aussi des changements dans les quantités thermodynamiques utilisées, en particulier l’utilisation de la rothalpie à la place de l’enthalpie d’arrêt pour déterminer le couple dû aux phénomènes irréversibles. Une application de cette méthode est présentée sur un rotor quadripale créé pour cette étude et montre comment cette nouvelle approche peut améliorer la précision de l’extraction des performances d’un rotor à partir de résultat issu de la simulation numérique. / In this thesis, a formulation for “far-field” torque extraction in the case of a hovering rotor is presented. This formulation is derived from an aircraft “far-field” drag extraction method, based on van der Vooren and Destarac’s works [?, ?, ?]. A tool was previously developed at Onera to give an aerodynamic comprehensive analysis of aircraft drag, based on physical and local analysis of the computed flow field surrounding the aircraft. It decomposes the total drag, also called mechanical drag, into its physical components. These physical components can be defined as : 1) wave drag, 2) viscous drag, 3) induced drag. The adaptation of the method to a rotor in hover leads to consider rotor torque instead of aircraft drag, which gives the following decomposition : 1) wave torque, 2) viscous torque, 3) induced torque. Rotor simulations differ from aircraft ones inasmuch as the Euler (or RANS) equations are not written in the same reference frame : aircraft simulations use the relative velocity formulation while rotor simulations use the absolute velocity projected in the relative frame. This difference leads to two different formulations of the flow equations, and necessarily two different formulations of the drag or torque extraction. This change of reference frame also implies some changes in the thermodynamical quantities used, in particular the use of the rothalpy instead of the stagnation enthalpy to determine the torque due to irreversible phenomena. An application of this method is described on a four-bladed rotor created for this study and shows how this method can improve rotor performance extraction from numerical simulations.

No description available.

L’étude des propriétés luminescentes de nanoparticules permet d’accéder à des informations sur les mécanismes élémentaires liés à cette luminescence. À l’instar de ce qui a été fait pour les semiconducteurs (effets de confinement quantique par exemple), nous souhaitons étudier l’influence de paramètres tels que la taille ou la composition de nanoparticules isolantes sur leur luminescence. Pour cela il fallait créer un outil polyvalent capable d’exciter efficacement ces particules, d’en effectuer des images luminescentes et enfin d’en faire la spectroscopie. Le microscope confocal chromatique élaboré dans le cadre de mon travail de thèse et hébergé au sein de Nanoptec est à même de remplir ces objectifs : longueur d’onde d’excitation accordable allant de l’UV dur (210 nm) à l’IR (près de 1 μm), résolution spatiale de l’ordre du μm (permet l’étude de particules assez espacées), aspect confocal permettant d’isoler spatialement la luminescence de l’objet étudié, système de détection capable d’isoler spectralement cette luminescence... Cet outil a permis des collaborations diverses avec des équipes au sein et hors du laboratoire, comme la cartographie spatiale de la répartition de dopants dans des fibres laser, l’évaluation des inhomogénéités lumineuses au sein de matériaux céramiques, la mesure de dispersion spatiale de nanoparticules dans des plastiques... Le microscope confocal achromatique nous sert également à étudier plus fondamentalement les effets de la puissance d’excitation sur les propriétés luminescentes de nanoparticules de tailles et de compositions diverses. / Studying luminescent properties of nanoparticles leads to informations about elementary mechanisms connected to the luminescence. As it has been done for semiconductors (quantum confinement effect for instance), we want to evaluate the influence of parameters like size or composition of insulating nanoparticles on their luminescence. In this purpose, we had to develop a versatile tool, able to efficiently excite these particles, then perform their image and their spectroscopy. The achromatic confocal microscope built during my phD work and hosted in the Nanoptec center is able to fill these aims : tunable wavelenght from deep UV (210 nm) to IR (about 1 μm), spatial resolution of about 1 μm (enables us to work on sufficiently separated particules), confocal aspect leading to a spatial isolation of the studied object luminescence, detection system able to spectrally select this luminescence... We made various collaborations with teams in and out of the laboratory, such as spatial cartography of dopant distribution in laser fibers, evaluation of optical inhomogeneities amidst ceramics, spatial dispersion measurements of nanoparticles in plastics... The achromatic confocal microscope is also helpful for a better understanding of excitation power effects of luminescent properties of various sizes and compositions nanoparticles.

L'estimation précise de la traînée est aujourd'hui un enjeu majeur pour les avionneurs. Il est nécessaire d'identifier et de quantifier ses sources phénoménologiques dans le cadre d'un processus de design efficace. Les méthodes champ lointain, qui permettent une telle décomposition, sont cependant limitées aux applications stationnaires.Cette étude consiste à développer une méthode d'extraction champ lointain destinée à permettre une décomposition phénoménologique de la traînée pour des écoulements instationnaires. La première étape a consisté à généraliser la formulation stationnaire de Van der Vooren aux écoulements instationnaires. Des axes pour l'amélioration de la robustesse et du contenu physique ont ensuite été explorés, avec la mise en évidence de phénomènes acoustiques. La formulation ainsi obtenue a ensuite été appliquée à des cas tests simples, dans le but de valider la décomposition phénoménologique. Le comportement des composantes de traînée s'est avéré cohérent avec la physique de l'écoulement. Enfin, la méthode a été appliquée à des cas complexes afin de démontrer ses capacités : un cas instationnaire 3D ainsi qu'un écoulement simulé en ZDES.Dans l'avenir, il serait intéressant de continuer à explorer la définition de la composante de traînée induite, par exemple en utilisant les formulations basées sur le vecteur vitesse. En ce qui concerne les cas d'application, l'évaluation de la performance d'un doublet d'hélices contra-rotatives pourrait fortement bénéficier de l'utilisation d'une méthode comme celle-ci. Enfin, des applications en vol d'ailes battantes pourraient être d'intéressantes perspectives. / Accurate drag prediction is now of a major issue for aircraft designers. Its phenomenological sources need to be identified and quantified for an efficient design process. Far-field methods, which allow such phenomenological drag breakdown, are however restricted to steady flows. This study consists in developing a far-field drag prediction method aiming at a phenomenological breakdown of drag for unsteady flows. The first step has consisted in generalizing the steady formulation of Van der Vooren to unsteady flows, starting from a new rigorous proof. Axes for the improvement of the robustness and physical background have then been explored. Acoustic contributions have in particular been highlighted and quantified. The resulting five-components formulation has then been applied to simple cases, in order to validate as best as possible the phenomenological breakdown. The behavior of the drag components has proved to be consistent with the physics of the flow. Finally, the method has been applied to complex cases in order to demonstrate its capabilities: a 3-D case and a flow simulated by the ZDES method. In the future, it would be interesting to further improve the definition of the induced drag component, for example by using velocity-based formulations. As far as the application cases are concerned, the performance evaluation of a Counter-Rotating-Open-Rotor would strongly benefit from such a method. Unsteady optimization of one of the drag component could also be contemplated. Finally, applications in aeroelasticity or flapping flight would be an interesting perspective.