Local helioseismology consists of methods which study the propagation of the waves through the solar interior. The properties of the waves encode conditions in the plasma along their propagation trajectories. Local helioseismology allows us to learn about these conditions. The principal method utilised in this thesis is the time-distance local helioseismology. The time-distance method is based on measurements of travel times of the waves, hence it is sensitive especially to plasma flows and sound-speed perturbations, to which we focus. We utilised the inverse modelling, mainly using subtractive optimally localised averaging method with a minimisation of the cross-talk. This method was modified to allow for a simultaneous inversion of vector flows and sound-speed perturbation. This combination makes use of both the difference and the mean point-to-annulus averaging geometries of wave travel times in both the ridge and the phase-speed filtering approaches. The combined inversion provides us with more information about the inverted quantities. Moreover, the user can control the cross-talk and other important mathematical properties of the objects involved. The modified methodology was thoroughly tested. The main results may be summarised in five points. First, for successful inversions of the sound-speed...

Local helioseismology consists of methods which study the propagation of the waves through the solar interior. The properties of the waves encode conditions in the plasma along their propagation trajectories. Local helioseismology allows us to learn about these conditions. The principal method utilised in this thesis is the time-distance local helioseismology. The time-distance method is based on measurements of travel times of the waves, hence it is sensitive especially to plasma flows and sound-speed perturbations, to which we focus. We utilised the inverse modelling, mainly using subtractive optimally localised averaging method with a minimisation of the cross-talk. This method was modified to allow for a simultaneous inversion of vector flows and sound-speed perturbation. This combination makes use of both the difference and the mean point-to-annulus averaging geometries of wave travel times in both the ridge and the phase-speed filtering approaches. The combined inversion provides us with more information about the inverted quantities. Moreover, the user can control the cross-talk and other important mathematical properties of the objects involved. The modified methodology was thoroughly tested. The main results may be summarised in five points. First, for successful inversions of the sound-speed...

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<div>The objective of this doctoral research was to develop a versatile inverse heat transfer approach, that would enable the solution of small scale problems present in microelectronics, as well as the analysis of the complex heat flux in turbines. An inverse method is a mathematical approach which allows the resolution of problems starting from the solution. In a direct problem, the boundary conditions are given, and using the governing physics principles and equations you can calculate the solution or physical effect. In an inverse method, the solution is provided and through the physical equations, the boundary conditions can be determined. Therefore, the inverse method applied to heat transfer means that we know the variation of temperature (effect) over time and space. With the temperature input, the geometry, thermal properties of the test article and the heat diffusion equation, we can compute the spatially- and temporally-varying heat flux that generated the temperature map.</div><div><br></div><div>This doctoral dissertation develops two inverse methodologies: (1) an optimization methodology based on the conjugate gradient method and (2) a function specification method combined with a regularization technique, which is less robust but much faster. We implement these methodologies with commercial codes for solving conductive heat transfer with COMSOL and for conjugate heat transfer with ANSYS Fluent.</div><div><br></div><div>The goal is not only the development of the methods but also the validation of the techniques in two different fields with a common purpose: quantifying heat dissipation. The inverse methods were applied in the micro-scale to the dissipation of heat in microelectronics and in the macro-scale to the gas turbine engines.<br></div><div><br></div><div>In microelectronics, we performed numerical and experimental studies of the two developed inverse methodologies. The intent was to predict where heat is being dissipated and localized hot spots inside of the chip from limited measurements of the temperature outside of the chip. Here, infrared thermography of the chip surface is the input to the inverse methods leveraging thermal model of the chip. Furthermore, we combined the inverse methodology with a Kriging interpolation technique with genetic algorithm optimization to optimize the location and number of the temperature sensors inside of the chip required to accurately predict the thermal behavior of the microchip at each moment of time and everywhere.<br></div><div><br></div><div>In the application for gas turbine engines, the inverse method can be useful to detect or predict the conditions inside of the turbine by taking measurements in the outer casing. Therefore, the objective is the experimental validation of the technique in a wind tunnel especially designed with optical access for non-contact measurement techniques. We measured the temperature of the outer casing of the turbine rotor with an infrared camera and surface temperature sensors and this information is the input of the two methodologies developed in order to predict which the heat flux through the turbine casing. A new facility, specifically, an annular turbine cascade, was designed to be able to measure the relative frame of the rotor from the absolute frame. In order to get valuable data of the heat flux in a real engine, we need to replicate the Mach, Reynolds, and temperature ratios between fluid and solid. Therefore, the facility can reproduce a large range of pressures and flow temperatures. Because some regions of interest are not accessible, this researchprovides a significant benefit for understanding the system performance from limited data. With inverse methods, we can measure the outside of objects and provide an accurate prediction of the behavior of the complete system. This information is relevant not only for new designs of gas turbines or microchips, but also for old designs where due to lack of prevision there are not enough sensors to monitor the thermal behavior of the studied system.<br></div><div><br></div>

Ce travail porte sur le développement de nouvelles méthodes de mesure permettant la caractérisation de réactions chimiques très exothermiques dans des conditions de sécurité. Pour cela, nous souhaitons combiner l’analyse thermique des réactions et la technologie microfluidique. L’utilisation de la microfluidique rend possible l’utilisation de très faibles volumes réactionnels limitant ainsi tout risque lié à la dangerosité des réactions explosives. Le premier appareil développé est un microcalorimètre qui mesure le flux de chaleur global dégagé lors d’un écoulement co-courant ou gouttes. Plusieurs paramètres peuvent être déterminés : enthalpie de mélange et de réaction, concentration par dosage calorimétrique et cinétique. Le deuxième dispositif consiste à mesurer le champ de température du milliréacteur isopéribolique à l’aide d’une caméra InfraRouge et ainsi de suivre localement l’évolution de la réaction pour déterminer les paramètres thermocinétiques. / This work deals with the development of new measurement methods in order to characterize high exothermic chemical reactions in safe conditions. Thus, we combine thermal analysis with microfluidic technology. The use of microfluidics allows to manipulate a very small amount of product safely. First, we have developed a microcalorimeter to measure the global heat flux produced in co-flow or droplet-flow configurations. Several parameters can be determined: reaction and mixing enthalpy, concentrations by calorimetric titration and kinetics. The second method uses an InfraRed camera to measure the temperature field of the isoperibolic millireactor. Then, the local evolution of the reaction is estimated by thermal processing. From such inverse methods, the thermokinetic parameters can be determined.

Les mesures optiques dimensionnelles sont des techniques en plein essor dont la maîtrise et l'exploitation soulèvent encore de nombreuses questions. Pour une meilleure compréhension d'un système de mesure par stéréo-corrélation d'images, des études de caractérisation et d'évaluation de l'erreur de mesure en corrélation à partir d'images synthétiques et en stéréovision à partir d'images réelles ont été réalisées. Les résultats mettent en avant l'influence de plusieurs paramètres : fenêtre de corrélation, déformation et gradient de déformation. La dernière partie de l'étude est consacrée à l'identification de comportements constitutifs à partir des mesures de champs. Deux méthodes sont mises en œuvre : la méthode des champs virtuel pour l'identification des paramètres élastiques d'un matériau et l'identification paramétrique par recalage éléments finis pour le cas des comportements élasto-plastiques. / The optical dimensional measurements are emergent techniques whose control and exploitation still address many questions. For a better understanding of the stereo-correlation measurement systems, studies are made to characterize and assess the digital image correlation measurement error by the way of synthetic images. The stereovision characterization is made using real images. The results highlight the influence of several parameters : subset size, strain and strain gradient. The last part of this study is devoted to the identification of constitutive behaviour law using full-field measurements. Two identification methods are used : the virtual fields method to determine the elastic parameters of a material and the finite element model updating method to identify the elasto-plastic behaviour law.

[Truncated abstract] The process of selective withdrawal has, over many years, been used as an effective tool for extraction of water of particular quality from stratifed reservoirs. While the formation and steady-state theory of selective withdrawal in a stratifed fluid at rest has been extensively studied, little is known how vertical displacements of stratifcation due to long internal waves affect the water quality of the outflows. The first part of this study investigates the effect of basin-scale internal waves on the water quality parameters in Lake Burragorang, a large water supply reservoir for the city of Sydney, Australia. It is shown from field observations how the steady-state formulation of selective withdrawal can be used to predict the outflow water quality in reservoirs where internal waves are present, with a temperature prediction accuracy within 0.2 oC. . . In order to explain fluctuations in water quality parameters of the outflows, such as turbidity, it is important to know not only the stratifcation conditions in front to the offtake, but also to understand the dynamics of suspended particles in the upper reaches of the reservoir. In the third part of this study, transport and settling of suspended particles was investigated in the Wollondilly arm of Lake Burragorang by combination of direct and inverse methods. The inverse method was modifed to enable the separation of advective and diffusive transport of suspended particles from Stokes settling controlled by gravity, yielding twodimensional fields of particle velocities and settling fluxes in the upper reaches of the reservoir. These estimates are compared to the direct measurements of sedimentation fluxes made by the sediment traps and LISST-100.

Cette thèse est une contribution à la caractérisation des fonds sous-marins par des techniques acoustiques. On s'intéresse aux fonds sédimentaires, principalement sédiments sableux. Les fonds de sables sont en effet fréquemment rencontrés par petits fonds sous nos latitudes. Les procédés existants de caractérisation acoustique des fonds visent le plus souvent à qualifier la géométrie du sol ou du sous-sol: morphologie du fond, typologie des faciès sédimentaires, identification du toit rocheux ... Toutefois, les détails du sous-sol marin (stratification et composition des sables) nous échappent le plus souvent et on a alors recours à des sondages in-situ ponctuels, coûteux et souvent difficiles à réaliser. Afin de résoudre ce problème, nous avons développé SCAMPI (Système de Caractérisation Acoustique Marine Propagation Interface). C'est un dispositif de caractérisation géoacoustique breveté qui vise justement à réduire notre myopie chronique dans les premiers mètres des sous-sols sableux immergés en calculant des profils verticaux des vitesses du son. Le système développé est typique d'un processus d'inversion basé sur des mesures distantes et indirectes (on ne touche pas le sol). Disposer de profils de vitesses pour caractériser le sous-sol est une étape nécessaire, mais insuffisante pour les applications visées. Pour ces dernières, il s’agit notamment de déterminer si le sable est fin ou grossier, s'il est homogène ou hétérogène, s'il contient des coquilles, s'il est compacté ou pas.Pour répondre à de telles questions, il est nécessaire d'utiliser des relations entre les vitesses du son et les propriétés des matériaux granulaires. Ces relations géoacoustiques sont quasi-inexistantes pour les sables marins, surtout pour les sables grossiers. Pour constituer de nouvelles relations géoacoustiques, il est proposé d’établir des bases de données à partir de mesures in-situ des vitesses acoustiques et des analyses des échantillons de sédiments prélevés au même endroit. Pour cela, un prototype de célérimètre a été développé, INSEA (INvestigation of SEdiment by means of Acoustic), qui permet de mesurer les vitesses et l'atténuation du son dans des sédiments, y compris dans des sables grossiers. / This thesis is a contribution to the seabed exploration by means of acoustical methods. We focus on sediment seabeds, especially on sand sediments because there are often encountered off European coasts. Existing acoustic methods for seabed characterization generally aim to qualify the sub-seafloor: sediment thickness or bedrock cap detection.Nevertheless, accurate sediment stratification or details of the involved sediment are generally out of reach. This is why SCAMPI (Sub-seafloor Characterization by Acoustic Measurements & Parameters Inversion) have been have designed. This patented device is a geoacoustical inversion method based on an underwater acoustic instrumentation towed in water column. It aims to identify and characterize sediment layers over a thickness of 5-10 meters below the seabed, quantifying major physical parameters as compressional speed. But vertical sound speed profiles of the sub-seabed is a necessary step but is insufficient to predict refined information about the sediment: is it coarse, homogeneous, does it contain inclusions ..?To give answers to these questions, geoacoustical relations linking acoustic parameters to sedimentological parameters are required. But these relations are sparse, particular for coarse sands.A velocimeter prototype INSEA (INvestigation of SEdiment by means of Acoustic) have been designed, to measure in situ acoustical parameters of the first centimeters of the seafloor, even in coarse sands. This work is the preliminary work leading to a new project which consist in building specific data bases to elaborate these geoacoustical relations and theoretical modeling in granular wet media suited to marine geophysics applications.

La connaissance et la maitrise de la température et de la concentration des produits de combustion sont des paramètres clés pour la compréhension et l’amélioration de l’efficacité des moteurs. La mesure de ces température et concentration permettrait d’améliorer les machines de combustion et de quantifier les rejets polluants dans l’air (tels que le CO, CO2, NO, NO2, SO2, les aérosols, les suies ainsi que les composés organiques volatils) qui sont des enjeux environnementaux importants. Les procédés de combustion sont inhomogènes. Les méthodes actuelles sont essentiellement des méthodes de détection et pas de quantification. Nous proposons une méthode originale de caractérisation des profils de température et concentration couplant les avantages d’une mesure active par rétrodiffusion (LIDAR-Rayleigh, Light Detection And Ranging) d’une impulsion laser fondée sur la diffusion Rayleigh avec une mesure passive par spectroscopie d’émission. La première méthode est sensible aux profils spatiaux de températures et la seconde est particulièrement sensible à la température maximale et concentration des gaz. Cette étude a été soutenue par une REI (Recherche Exploratoire et Innovation) : « Caractérisation par Émission et LIDAR d’Écoulements de Propulseurs » en collaboration avec le laboratoire FEMTO-ST de Belfort, l’ONERA et l’entreprise MBDA. / The knowledge and control of the temperature and concentration of combustion products are key parameters to understand and improve engine efficiency. The measurement of temperature and concentration will improve combustion machines and quantify the pollutant emissions in the air (such as CO, CO2, NO, NO2, SO2, aerosols, soot and volatile organic compounds) which are important environmental issues. Combustion processes are inhomogeneous. Current methods are substantially methods for the detection and not for quantification. We propose an original method based on the characterization of temperature and concentration profiles coupling the benefits of an active backscattering method (Rayleigh LIDAR, Light Detection And Ranging) of a laser pulse with passive spectroscopic measurements. The first method is based on Rayleigh scattering and is sensitive to spatial temperature profiles and the second is particularly sensitive to the maximum temperature and to gas concentration. This study was supported by REI (Exploratory Research and Innovation): " Flows thrusters characterization by emission and LIDAR " in collaboration with the FEMTO-ST laboratory located in Belfort, ONERA and the MBDA company.

Le sujet de l'étude concerne la caractérisation des propriétés thermiques de liquides semi-transparents à haute température : les liquides silicatés. La caractérisation de ces matériaux est particulièrement délicate car il faut séparer les contributions des différents modes de transfert thermique (conduction, convection et rayonnement) si l'on veut mesurer des propriétés intrinsèques. Le dispositif expérimental est basé sur une méthode pulsée de type flash. La cellule de mesure, placée au centre d'un four tubulaire, est soumise à une excitation délivrée par un laser continu et l'élévation de température est mesurée à l'aide d'un détecteur infrarouge sur la face opposée à l'excitation. La modélisation du problème direct prend en compte le couplage conducto-radiatif en résolvant l'équation de la chaleur en régime transitoire et l'équation de transfert radiatif (ETR) pour un milieu gris émettant, absorbant et non diffusant à l'aide de la méthode des harmoniques sphériques (approximation P1). La méthode développée permet d'estimer simultanément la diffusivité thermique et un coefficient d'absorption moyen (gris) par méthode inverse. Les résultats expérimentaux obtenus sur des liquides silicatés présentant des propriétés radiatives différentes (i.e., des coefficients d'absorption différents) valident la méthode de caractérisation développée et mise en œuvre dans nos travaux / The study deals with the characterization of the thermal properties of semi-transparent liquids at high temperature: molten silicates. The characterization of such materials is particularly challenging because the contributions of the different heat transfer modes (conduction, convection and radiation) should be accounted for to allow the measurement of intrinsic properties. The experimental setup is based on a transient pulse method derived from the flash method. A heat flux stimulation is generated on the front face of an experimental cell, placed at the center of a tube furnace, with a continuous laser beam and the temperature rise is measured by an infrared detector on the opposite side. The modeling of the direct problem takes into account the conducto-radiative coupling by solving both the heat equation and the radiative transfer equation (RTE) for a gray emitting, absorbing but non-scattering medium with the spherical harmonics method (P1 approximation). The developed method allows to simultaneously estimate the thermal diffusivity and a mean (gray) absorption coefficient by an inverse method. The experimental results obtained on molten silicates with different radiative properties (i.e., different absorption coefficients) validate the characterization method developed and implemented in our work