Un modèle semi-analytique permettant de simuler le transfert thermique conjugué dans un mini/macro canal plan soumis à des sources de chaleur surfaciques localisées sur les faces externes et variantes en fonction du temps, a été présenté et vérifié. Plus le diamètre hydraulique du canal est petit, plus la caractérisation expérimentale interne (mesure des températures et des flux) en régime thermique permanent ou transitoire à l'aide des capteurs internes est délicate. Une méthode non-intrusive permettant d'estimer les conditions internes à partir des mesures de température par thermographie infrarouge sur les faces externes et d'un modèle semi-analytique, a été effectuée. Comme le coefficient de transfert convectif forcé classique perd son sens en régime instationnaire, une approche alternative basée sur une fonction de transfert, valable pour un système linaire et invariant dans le temps a été mise en œuvre. Cette fonction peut être calculée analytiquement (uniquement pour une géométrie simple) ou estimée expérimentalement (géométrie complexe). Grâce au caractère intrinsèque de cette fonction de transfert, deux capteurs virtuels ont été conçus : capteur virtuel de température et détecteur d'encrassement permettent respectivement d'estimer les températures internes et de détecter l'encrassement qui peut avoir lieu dans l'échangeur à partir des mesures de températures sur les faces externes / A semi-analytical model allowing to simulate the transient conjugate heat transfer in mini/macro plane channel subject to a heat source(s) localized on the external face(s), was presented and verified. The developed model takes into account advection-diffusion in the fluid and conduction in the solid. As the hydraulic diameter of the channel becomes small, the internal experimental characterization (measurement of temperature and heat flux) using internal sensors become tricky because internal sensors located may compromise the structural integrity of the whole system. A non-intrusive method for estimating the internal conditions from infrared temperature measurements on the external faces using the semi-analytical model was performed. Since the classic convective heat transfer coefficient loses its meaning in transient state, an alternative approach based on a transfer function, valid for Linear Time-Invariant (LTI) systems, was highlighted. This function can be calculated analytically only for a simple geometry. For complex geometries it can be estimated experimentally. Thanks to intrinsic character of this function, two characterization methods were designed. The first to estimate the temperature at a point from a measurement at another point in the system (virtual temperature sensor). The second method concerns the detection of fouling layers that may appear in the heat exchanger from temperature measurements on the external faces

O estímulo vibratório gerado pela utilização das plataformas vibratórias tem sido aplicado como método eficaz para promover desempenho esportivo e também na reabilitação de pacientes com diversificadas disfunções. Acredita-se que a vibração de corpo inteiro (VCI) é capaz de diminuir os déficits de ativação muscular voluntária através de reflexos de estiramento neuromuscular, tornando-se um meio eficaz e de fácil aplicabilidade para pacientes com maiores incapacitações. Resultados controversos na literatura, com relação aos benefícios dos estímulos vibratórios, tornam a escolha dos parâmetros do equipamento (frequência, amplitude, tempo de exposição e modo de vibração) um desafio na obtenção dos melhores resultados. Assim, o objetivo desta tese visa a avaliação dos efeitos fisiológicos agudos da vibração de corpo inteiro (sensibilidade cutânea tátil e dolorosa, equilíbrio, temperatura superficial da pele, transmissibilidade da vibração) e a construção de um mapa de percepção corporal da VCI. Foram utilizados diferentes parâmetros e marcas desses equipamentos. Para investigar cada variável, quatro diferentes estudos foram realizados separadamente. O primeiro estudo investigou os efeitos da VCI na sensibilidade cutânea vibratória medidos a 30 Hz (corpúsculos de Meissner) e 200Hz (corpúsculos de Pacini) e de toque-pressão dos pés de 20 sujeitos normais e o tempo de duração dos efeitos da vibração nesses receptores. Como principais resultados, foram constatadas que as descargas aferentes dos mecanorreceptores de adaptação rápida foram fortemente afetadas pela vibração assim como a sensibilidade de toquepressão. Após 10 min de exposição à VCI o tempo de recuperação para a sensibilidade voltar aos limiares basais nos pés foi entre 2 e 3 h. Para continuar elucidando os efeitos agudos pós-exercício com vibração, um segundo estudo foi realizado avaliando variáveis fisiológicas em quatro diferentes frequências de exposição de VCI (30, 35, 40, 44 Hz). Foram avaliadas pressão arterial, frequências cardíaca e respiratória, temperatura axilar e a temperatura cutânea através de termografia por infravermelho dos membros inferiores dos 24 participantes avaliados. Por fim, o equilibro desses indivíduos foi avaliado através das análises dos deslocamentos, da velocidade e da área do centro de pressão (COP), em uma plataforma de força. Os dados do segundo estudo mostraram que, para as frequências de 40 e 44 Hz do equipamento, houve uma alteração significativa para as variáveis velocidade e comprimento ântero-posterior do centro de pressão. Além disso, durante a vibração e 10 min após, a temperatura dos membros inferiores foi reduzida, provavelmente em virtude da vasoconstrição gerada. Na investigação da sensibilidade dolorosa um terceiro estudo foi proposto, tendo em vista que as vias dos mecanorreceptores de sensibilidade cutânea tátil diferem daqueles relacionados com a sensibilidade dolorosa. Um modelo de dor crônica com ratos Wistar foi realizado e os animais foram tratados com VCI, esteira e a combinação de esteira com VCI. Como principais resultados deste estudo, os grupos tratados com VCI mostraram redução significativa da sensibilidade de toque-pressão após todas as sessões em comparação aos demais grupos. Efeitos analgésicos através do tempo de latência medidos com o hot plate foram encontrados após o terceiro dia de tratamento com 5 min de exposição por dia à VCI, nos primeiros 5 dias e 10 min nos 5 dias subsequentes. Como finalização das variáveis de interesse, o último estudo combinou dados quantitativos advindos da acelerometria (com medições na cabeça, quadril e tíbia) com dados qualitativos através da escala de Borg. Sessenta e cinco adultosjovens foram avaliados e este estudo propôs um método para escolher os diversificados parâmetros da plataforma vibratória, para alcançar os efeitos desejados na reabilitação ou desempenho esportivo. Este estudo mostrou que os índices de percepção de severidade medidos através da escala de Borg corresponderam com os dados quantitativos da acelerometria e assim os parâmetros do equipamento podem ser escolhidos com base na sensação subjetiva proveniente da escala de Borg. Os níveis de desconforto no equipamento podem estar relacionados com a frequência de ressonância das diferentes partes do corpo. Futuros estudos devem considerar aplicações clínicas da plataforma vibratória em pacientes com dor crônica musculoesquelética utilizando o modelo para escolha dos parâmetros do equipamento proposto nesta tese. / The vibratory stimuli generated by the use of vibrating platforms have been used as an effective method to promote sports performance and also in the rehabilitation of patients with several dysfunctions. It is believed that the whole body vibration (WBV) is able to decrease the deficits in voluntary muscle activation by neuromuscular stretch reflexes making it an efficient and easy exercise method applied to patients with greater disabilities. Controversial results in the literature regarding the benefits of the vibratory stimuli make the choice of the equipment parameters (frequency, amplitude, time of exposure and vibration mode) a challenge in getting the best results. The goal of this dissertation involves the evaluation of the acute physiological effects of whole body vibration (skin tactile and pain sensitivity, balance, skin temperature and vibration transmissibility) and the construction of a WBV perception body map. Parameters settings and different brands of these devices were used. To investigate each variable, four different studies were conducted separately. The first study investigated the effects of WBV on fast adapting mechanoreceptors measured at 30 Hz (Meissner corpuscles) and 200Hz (Pacinian corpuscles) and touch-pressure sensitivity from the right foot of 20 health subjects and the duration of the vibration effects on these receptors. The main results show that the afferent discharges of the fast adapting mechanoreceptors are strongly affected by vibration and sensitivity of touch-pressure was also impaired. After a single 10 minutes exposure to WBV, the time required to recover baseline tactile sensitivity on the feet was between 2 and 3 hours. To further elucidate the acute postexercise vibration effects, a second study was conducted assessing physiological variables at four different WBV frequencies (31, 35, 40, 44 Hz). Blood pressure, heart and respiratory rates, skin temperature and balance were measured. Skin temperature was measured by an infrared thermography of the lower limbs of 24 subjects. Balance was accessed with a force plate through the analysis of the center of pressure (COP) velocity, area and displacements variables. The results from this study show that for 40 and 44 Hz of the device’s frequencies, a significant decrease in balance was found for the center of pressure variables velocity and anterior-posterior displacement. Also, during WBV exposition and 10 minutes post vibration, the temperature of the lower limbs was reduced, probably due to vasoconstriction. To investigate the variable "pain", a third study was proposed, considering that the pathways and receptors of the cutaneous touch-pressure and vibration sensitivity differ from those related to pain sensitivity, the C and A fibers. A chronic pain model was applied in male Wistar rats and the animals were treated with WBV exercise (vibration platform), a low intensity exercise (treadmill) and a combined treatment involving both. The main results show that the groups treated with WBV showed a significant reduction in sensitivity to touchpressure after every session compared to the other groups. Analgesic effects through the time latency measured by the hot plate were found after the third treatment day with 5 min of exposure to WBV during the first 5 days and 10 min next 5 days. As completion of the fourth variable of interest, the last study by deriving quantitative data from accelerometry (with measurements on the head, hip and tibia) was combined with qualitative data arising from the Borg scale. Sixty five health young adults were measured and the study proposes a method for choosing the parameters settings of the vibrating platform, to achieve the desired goals in rehabilitation or sports performance. Discomfort perception ratings measured by the Borg scale corresponded well with the measured acceleration magnitudes and so the parameters settings of the device can be chosen based on the subjective sensation from the Borg scale. The level of discomfort ratings might be related to the frequency resonance phenomena of body parts. Future clinical applications with vibration platform in patients with muscle-skeletal chronic pain should be considered applying the model for choosing the parameter settings of the device proposed in this dissertation.

La compréhension des phénomènes se déroulant lors de l’impact d’une goutte sur une paroi chaude est essentielle à l’optimisation des systèmes de refroidissement par sprays. Lorsque la température de paroi est élevée, un film de vapeur se forme quasi-instantanément entre la goutte et la paroi chaude. Ce film modifie le comportement hydrodynamique des gouttes et réduit considérablement les échanges de chaleur et de masse par rapport à un impact mouillant. La modélisation de ces phénomènes est complexe en raison des nombreux couplages entre les transferts de chaleur et de masse et la dynamique d’impact de la goutte. Pour aborder ce sujet, des techniques de mesure optiques ont été développées spécifiquement. L’imagerie de fluorescence induite par plan laser à deux couleurs permet de caractériser la distribution de la température à l’intérieur des gouttes. Des images du champ de température, résolues à la fois spatialement et temporellement, sont rendues possible grâce à l’utilisation d’un nouveau couple de colorants fluorescents conservant une grande sensibilité à la température quand ils sont excités par un laser pulsé nanoseconde d’une énergie de plusieurs centaines de mJ. En parallèle, la thermographie infrarouge a été utilisée pour déterminer la température de la surface d’impact en saphir. Pour cela, cette dernière est recouverte d’une couche de quelques centaines de nanomètres de TiAlN, émissif dans l’IR alors que le saphir est transparent. Les images haute cadence sont analysées par un modèle d’inversion, prenant en compte la conduction thermique dans le saphir, afin d’estimer la densité de flux thermique au niveau de la surface d’impact. L’épaisseur du film de vapeur est également déduite de ces mesures sous l’hypothèse, justifiée a posteriori, d’une conduction thermique prépondérante dans le film de vapeur. Une étude de l’impact de gouttes d’eau est réalisée en faisant varier la vitesse d’impact et la température des gouttes avant impact, ainsi que la température de paroi. Dans la plupart des cas, la chaleur extraite à la paroi est comparable à celle transférée au liquide pour l’échauffer. Lorsque la température de paroi se rapproche et dépasse la température de Leidenfrost, les transferts de chaleur deviennent de plus en plus sensibles au nombre de Weber, et de moins en moins dépendant de la température de paroi. L’épaisseur du film de vapeur est affectée par des instabilités, dont les caractéristiques (longueur d’onde, amplitude) sont étudiées à partir des images IR. Finalement, un modèle 1D semi empirique est proposé pour décrire l’échauffement des gouttes et la croissance du film de vapeur. La pression exercée par la goutte sur le film de vapeur se dissipe très vite à l’impact, si bien que la croissance du film de vapeur est gouvernée par la conduction de la chaleur vers la goutte et non par la dynamique de l’impact / The understanding of phenomena occurring at the impact of a droplet onto a hot wall is crucial for the optimization of spray cooling systems. When the temperature of the wall is high, a vapor layer appears quasi-instantaneously between the droplet and le wall. This film of vapor modifies the hydrodynamic behavior of the droplet and highly reduce the heat and mass transfers in comparison with a wetting impact. Modelling these phenomena is complex because of the numerous coupling between the heat and mass transfers and the fluids dynamic. To get some insights into this phenomenon, optical diagnostic techniques have been developed. Two color planar laser induced fluorescence imaging allows characterizing the distribution of the temperature inside the droplet. Images of the temperature fields, resolved both spatially and temporally, are recorded thanks to the use of a couple of fluorescent dyes keeping a high temperature sensitivity even when they are excited by a nanosecond pulsed laser with and an energy of hundreds m J. In parallel, the infrared thermography is used to determine the temperature of the impinged surface made of sapphire. For that, this surface is coated with a thin film (about 300 nanometers) of TiAlN, highly emissive in the IR domain as opposed to the sapphire which is transparent in it. High frame rate image sequences are analyzed thanks to an analytical inversion model, taking into account the thermal conduction in the sapphire, in order to estimate the heat flux density at the impact surface. The thickness of the vapor layer was also deduced from this measurements thanks to the hypothesis of a dominant thermal conduction in the vapor layer. A study of water drop impact was performed with different impact speeds, wall temperatures and different drop injection temperatures. In most of the cases, the heat flux extracted from the wall in close to the flux transferred to the liquid phase of the droplet. When the wall temperature approaches or exceeds the Leidenfrost temperature, the transfers become more sensitive to the Weber number and less sensitive to the wall temperature. The vapor layer thickness is affected by instabilities whose caracteristics (wavelengths, amplitude) were investigated from the IR images. Eventually, a 1-Dsemi-empirical model is given for describing the heating of the liquid part of the droplet and the growth of vapor layer. The effect of the pressure exerted by the droplet onto the vapor film rapidly decreases during the impact process, so that the growth of the vapor film is only driven by the heat transferred by conduction to the droplet and not by dynamical parameters such as the impact velocity

Les industriels du secteur aéronautique sont, de plus en plus, à la recherche de procédés de fabrication à forte valeur ajoutée sans modifier les paramètres d’infusabilité de la résine lorsque l’on change de tissu. Nous avons donc mis en œuvre le procédé d’infusion de résine liquide sur des composites carbone/époxyde de forte épaisseur (e>4 mm) en modifiant les cycles de polymérisation, les matériaux utilisés et les séquences d’empilement. Tous les tissus sont en carbone et la résine utilisée est la résine commerciale RTM6. Les structures aéronautiques sont sollicitées, en service, de différentes façons. Elles peuvent être accidentellement impactées par des engins de maintenance, des outils, de la grêle ou toute autre forme d’impact. Le problème pour les industriels est de pouvoir détecter l’endommagement créé et de comprendre les mécanismes mis en jeu lors de l’impact mais aussi leur évolution pendant un cyclage en fatigue. Nos travaux se sont donc inscrits dans cet objectif et différentes méthodes ont été mises en œuvre : détection de défauts d’impact et suivi en temps réel par thermographie infrarouge, détection de l’indentation résiduelle par numérisation par projection de franges. Parallèlement, le phénomène d’impact a aussi été traité par une étude statistique par plan d’expérience et une modélisation avancée a été créée avec l’utilisation de surfaces cohésives. / Aeronautical manufacturers are looking for the best manufacturing process giving high benefits. Moreover, it has to be implemented easily with change of woven fabrics. So, we realize thick carbon/epoxy composites (t>4 mm) by modifying cure cycles, woven fabrics and lay-up sequences. Concerning the constituent materials of the composites, woven fabrics are carbon made and the resin is the commercial product named RTM6. Aeronautical structures can be unfortunately stressed, in service, with different solicitations: holding, engine impact, falling objects impacts or other way. The main problem for industrials is to be able to detect the created damage, to understand the phenomena dealing with it and the damage evolution during fatigue cycles. By following this direction, different methods are developed: impact damage defects detection and evolution monitored with infrared thermography, impact residual depth measurement by fringes projection digitalization. At the same time, a statistical study made by design of experiments is completed. A numerical impact modeling is also developed by using cohesive surfaces.

O estímulo vibratório gerado pela utilização das plataformas vibratórias tem sido aplicado como método eficaz para promover desempenho esportivo e também na reabilitação de pacientes com diversificadas disfunções. Acredita-se que a vibração de corpo inteiro (VCI) é capaz de diminuir os déficits de ativação muscular voluntária através de reflexos de estiramento neuromuscular, tornando-se um meio eficaz e de fácil aplicabilidade para pacientes com maiores incapacitações. Resultados controversos na literatura, com relação aos benefícios dos estímulos vibratórios, tornam a escolha dos parâmetros do equipamento (frequência, amplitude, tempo de exposição e modo de vibração) um desafio na obtenção dos melhores resultados. Assim, o objetivo desta tese visa a avaliação dos efeitos fisiológicos agudos da vibração de corpo inteiro (sensibilidade cutânea tátil e dolorosa, equilíbrio, temperatura superficial da pele, transmissibilidade da vibração) e a construção de um mapa de percepção corporal da VCI. Foram utilizados diferentes parâmetros e marcas desses equipamentos. Para investigar cada variável, quatro diferentes estudos foram realizados separadamente. O primeiro estudo investigou os efeitos da VCI na sensibilidade cutânea vibratória medidos a 30 Hz (corpúsculos de Meissner) e 200Hz (corpúsculos de Pacini) e de toque-pressão dos pés de 20 sujeitos normais e o tempo de duração dos efeitos da vibração nesses receptores. Como principais resultados, foram constatadas que as descargas aferentes dos mecanorreceptores de adaptação rápida foram fortemente afetadas pela vibração assim como a sensibilidade de toquepressão. Após 10 min de exposição à VCI o tempo de recuperação para a sensibilidade voltar aos limiares basais nos pés foi entre 2 e 3 h. Para continuar elucidando os efeitos agudos pós-exercício com vibração, um segundo estudo foi realizado avaliando variáveis fisiológicas em quatro diferentes frequências de exposição de VCI (30, 35, 40, 44 Hz). Foram avaliadas pressão arterial, frequências cardíaca e respiratória, temperatura axilar e a temperatura cutânea através de termografia por infravermelho dos membros inferiores dos 24 participantes avaliados. Por fim, o equilibro desses indivíduos foi avaliado através das análises dos deslocamentos, da velocidade e da área do centro de pressão (COP), em uma plataforma de força. Os dados do segundo estudo mostraram que, para as frequências de 40 e 44 Hz do equipamento, houve uma alteração significativa para as variáveis velocidade e comprimento ântero-posterior do centro de pressão. Além disso, durante a vibração e 10 min após, a temperatura dos membros inferiores foi reduzida, provavelmente em virtude da vasoconstrição gerada. Na investigação da sensibilidade dolorosa um terceiro estudo foi proposto, tendo em vista que as vias dos mecanorreceptores de sensibilidade cutânea tátil diferem daqueles relacionados com a sensibilidade dolorosa. Um modelo de dor crônica com ratos Wistar foi realizado e os animais foram tratados com VCI, esteira e a combinação de esteira com VCI. Como principais resultados deste estudo, os grupos tratados com VCI mostraram redução significativa da sensibilidade de toque-pressão após todas as sessões em comparação aos demais grupos. Efeitos analgésicos através do tempo de latência medidos com o hot plate foram encontrados após o terceiro dia de tratamento com 5 min de exposição por dia à VCI, nos primeiros 5 dias e 10 min nos 5 dias subsequentes. Como finalização das variáveis de interesse, o último estudo combinou dados quantitativos advindos da acelerometria (com medições na cabeça, quadril e tíbia) com dados qualitativos através da escala de Borg. Sessenta e cinco adultosjovens foram avaliados e este estudo propôs um método para escolher os diversificados parâmetros da plataforma vibratória, para alcançar os efeitos desejados na reabilitação ou desempenho esportivo. Este estudo mostrou que os índices de percepção de severidade medidos através da escala de Borg corresponderam com os dados quantitativos da acelerometria e assim os parâmetros do equipamento podem ser escolhidos com base na sensação subjetiva proveniente da escala de Borg. Os níveis de desconforto no equipamento podem estar relacionados com a frequência de ressonância das diferentes partes do corpo. Futuros estudos devem considerar aplicações clínicas da plataforma vibratória em pacientes com dor crônica musculoesquelética utilizando o modelo para escolha dos parâmetros do equipamento proposto nesta tese. / The vibratory stimuli generated by the use of vibrating platforms have been used as an effective method to promote sports performance and also in the rehabilitation of patients with several dysfunctions. It is believed that the whole body vibration (WBV) is able to decrease the deficits in voluntary muscle activation by neuromuscular stretch reflexes making it an efficient and easy exercise method applied to patients with greater disabilities. Controversial results in the literature regarding the benefits of the vibratory stimuli make the choice of the equipment parameters (frequency, amplitude, time of exposure and vibration mode) a challenge in getting the best results. The goal of this dissertation involves the evaluation of the acute physiological effects of whole body vibration (skin tactile and pain sensitivity, balance, skin temperature and vibration transmissibility) and the construction of a WBV perception body map. Parameters settings and different brands of these devices were used. To investigate each variable, four different studies were conducted separately. The first study investigated the effects of WBV on fast adapting mechanoreceptors measured at 30 Hz (Meissner corpuscles) and 200Hz (Pacinian corpuscles) and touch-pressure sensitivity from the right foot of 20 health subjects and the duration of the vibration effects on these receptors. The main results show that the afferent discharges of the fast adapting mechanoreceptors are strongly affected by vibration and sensitivity of touch-pressure was also impaired. After a single 10 minutes exposure to WBV, the time required to recover baseline tactile sensitivity on the feet was between 2 and 3 hours. To further elucidate the acute postexercise vibration effects, a second study was conducted assessing physiological variables at four different WBV frequencies (31, 35, 40, 44 Hz). Blood pressure, heart and respiratory rates, skin temperature and balance were measured. Skin temperature was measured by an infrared thermography of the lower limbs of 24 subjects. Balance was accessed with a force plate through the analysis of the center of pressure (COP) velocity, area and displacements variables. The results from this study show that for 40 and 44 Hz of the device’s frequencies, a significant decrease in balance was found for the center of pressure variables velocity and anterior-posterior displacement. Also, during WBV exposition and 10 minutes post vibration, the temperature of the lower limbs was reduced, probably due to vasoconstriction. To investigate the variable "pain", a third study was proposed, considering that the pathways and receptors of the cutaneous touch-pressure and vibration sensitivity differ from those related to pain sensitivity, the C and A fibers. A chronic pain model was applied in male Wistar rats and the animals were treated with WBV exercise (vibration platform), a low intensity exercise (treadmill) and a combined treatment involving both. The main results show that the groups treated with WBV showed a significant reduction in sensitivity to touchpressure after every session compared to the other groups. Analgesic effects through the time latency measured by the hot plate were found after the third treatment day with 5 min of exposure to WBV during the first 5 days and 10 min next 5 days. As completion of the fourth variable of interest, the last study by deriving quantitative data from accelerometry (with measurements on the head, hip and tibia) was combined with qualitative data arising from the Borg scale. Sixty five health young adults were measured and the study proposes a method for choosing the parameters settings of the vibrating platform, to achieve the desired goals in rehabilitation or sports performance. Discomfort perception ratings measured by the Borg scale corresponded well with the measured acceleration magnitudes and so the parameters settings of the device can be chosen based on the subjective sensation from the Borg scale. The level of discomfort ratings might be related to the frequency resonance phenomena of body parts. Future clinical applications with vibration platform in patients with muscle-skeletal chronic pain should be considered applying the model for choosing the parameter settings of the device proposed in this dissertation.

Un système microfluidique à onde élastique de surface a été développé dans le but de réaliser une réaction d'amplification de brins d'ADN par PCR. Nous avons principalement étudié la température et l'uniformité de l'échauffement des gouttes irradiées par des ondes de type Rayleigh. Ces dernières sont générées à la surface d'un substrat piézoélectrique de Niobate de Lithium (LiNbO3). Nous avons pensé un système consommant le moins d'énergie électrique possible pour atteindre les températures désirées et permettant une meilleure uniformité de la température des gouttes. Pour cela, un dispositif à transducteur enterré a été réalisé sous une couche isolante de silice. Les gouttes sont ainsi directement posées sur le transducteur ce qui limite les pertes et améliore la répartition de la chaleur au sein des gouttes. Nous avons ensuite vérifié que les réactifs de la PCR ne sont pas affectés par les ondes de Rayleigh ce qui laisse présager que la PCR peut être réalisée à l'aide d'un système d'échauffement par ondes de Rayleigh. Par ailleurs, le déplacement de goutte sur ce type de substrat de LiNbO3 est important pour des applications de type laboratoire sur puce. Ce substrat ayant des propriétés hydrophiles, des revêtements ont été développés afin de minimiser la force nécessaire à l'actionnement des gouttes. Dans ces travaux, nous proposons un nouveau type de couche à base de copolymère P(VDF-TrFe) dont la fabrication est simplement réalisée par dissolution et étalement par spin-coating. Nous avons montré que ce type de couche n'affecte que très peu la propagation des ondes de Rayleigh et les propriétés hydrophobes sont équivalentes à d'autres revêtements / In this work, a microfluidic system based on surface acoustic wave has been developed in order to achieve the amplification of DNA strands by temperature cycling (PCR). We studied mainly the temperature and the heat uniformity of microdroplets irradiated by Rayleigh waves. These waves are generated at the surface of a lithium niobate substrate. We propose a system allowing better temperature uniformity within microdroplets with an optimal energy consumption. For this, a device with buried transducer has been developed under an insulating layer (Silice). The droplets are then placed directly on the transducer which limits losses and improves the distribution of heat within the microdroplets. We then verified that the PCR reagents are not affected by the Rayleigh waves which suggests that PCR can be performed using a heating system by Rayleigh waves. Moreover, the move of microdroplets on this kind of LiNbO3 substrate is important for lab on chip applications. This substrate having hydrophilic properties, some coatings have been developed to minimize the required force to actuate the microdroplets. In this work, we developed a new hydrophobic layer based on copolymer P(VDF-TrFe) whose production is simply made by dissolving and spreading by spin-coating. We have shown that this kind of layer is compatible with Rayleigh waves and that the hydrophobic properties are equivalent to other coatings

Les impacts de gouttes sur paroi chaude sont présents dans de multiples domaines, tels que l'injection de diesel sous forme de spray dans des moteurs à combustions internes, ou le traitement thermiques de l'acier dans le domaine de la sidérurgie. L'étude de l'interactions goutte/paroi permet de mieux comprendre les phénomènes thermiques mis en jeu, et ainsi d'aboutir à des économies d'énergies et d'eau. De nombreux travaux portent sur cette thématique, mais ils présentent des résultats divergents et uniquement basés sur l'étude de la paroi chaude. Cette thèse a pour but d'apporter des mesures expérimentales sur les caractéristiques inconnues en étudiant les gouttes. Pour cela, un dispositif expérimental a été mis au point afin de mener à bien l'ensemble des mesures souhaitées. Les diverses techniques de mesures de température utilisées sont présentées, et une attention plus particulière a été portée sur le développement de la technique de fluorescence induite par plan laser qui permet d'accéder au champ de température des gouttes durant leur impact. Cette méthode, combinée à une technique de thermographie par caméra infrarouge couplée à un modèle de conduction inverse, permet d'extraire les paramètres concernant l'aspect thermique, et de déterminer de nouvelles caractéristiques inédites, telles que l'échauffement des gouttes, l'évaporation relative de celles-ci ou encore l'efficacité de refroidissement. Les parts respectives jouées par la chaleur sensible et l'évaporation des gouttes sont tirées de cette dernière. Enfin, l'aspect dynamique est également abordé aboutissant au développement d'une technique d'ombroscopie rapide. Cette dernière a permis, grâce à la combinaison de mesures de diamètres précises et d'une fréquence d'acquisition élevée, d'extraire les paramètres dynamiques de l'impact tels que la vitesse et taille des gouttes, ou d'autres paramètres relatif au type d'impact rencontrés à l'aide d'un algorithme de suivi de particules développé durant la thèse / The droplet impact onto a heated wall interaction can be found in mutiples fields, such as internal combustion engines or the steel industry, specially in the thermal treatment of the steel where high energy dissipation rate is required. The study of this interaction should grant a better understanding of this phenomena, and thus, allow the enhancement of these processes and reduce the energy and water consumption. Several studies have already been carried out on this subjet but a great majority of them, whose results present great divergence, only consider the heated wall, neglecting the outgoing of the droplet. This thesis put the emphasis on the liquid phase where currently no data exist to our knowledge, with the help of multiples experimental technics that have been developped. A general experimental setup has been made in order to make all the wanted measurements. The measurement techniques used in this study are first presented, to begin with the planar laser induced fluorescence, which allow us to know the droplet temperature during the impact. Used with an infrared thermography technique coupled with an inverse conduction model, it is possible to extract some important parameter regarding the thermal aspect, such as the droplet heating, the relative evaporation ratio or the cooling efficiency. This latter can be written as the sum of the two major contributions of the cooling: the sensible heat and the evaporation of the droplet. Finally, a high speed shadow imagery technique is presented. It has been developped in order to study the dynamic aspect of the droplet impact. This technique can determine several dynamic parameters such as the droplet speed and diameter, or other parameter regarding the type of impact encountered

Ce travail de recherche examine aux échelles globale et locale les caractéristiques thermo-hydrauliques au sein des échangeurs à plaques ondulées pour les écoulements monophasiques et en mode condensation. Il comprend deux parties :La première partie concerne l'analyse des structures d'écoulement en mode monophasique à partir d'un outil de simulations numériques, et dont les résultats sont validés à partir d'une campagne expérimentale. L'exploitation des résultats de simulations, à partir d'observables judicieusement sélectionnées, a permis de quantifier les grandes classes d'écoulement en fonction des paramètres géométriques et fluidiques de l'échangeur. Ce nouvel éclairement sur les structures d'écoulement a conduit à la proposition d'un modèle général original sur les lois de friction au sein de ces échangeurs de géométrie d'écoulement complexe.La deuxième partie concerne l'étude de la condensation de la vapeur avec et sans surchauffe en entrée de l'échangeur. Ainsi, un dispositif expérimental permettant le contrôle précis des conditions aux limites a été développé, et une métrologie spécifique, basée sur la thermographie infrarouge a également été mis au point, afin de remonter à certaines grandeurs locales le long du condenseur (titre de vapeur, coefficient d'échange thermique...). On observe ainsi une très forte variabilité des coefficients d'échanges thermiques et de la densité de flux de chaleur le long du condenseur, et la surchauffe de la vapeur tend à intensifier les transferts thermiques. Ce complément de mesures remet en question certaines hypothèses de la littérature quant à l'élaboration de corrélations sur les transferts de chaleur dans les condenseurs. / This research work examines at the global and local scales the thermo-hydraulic characteristics of plate heat exchangers with corrugated chevron plates, for single-phase and condensation flows. The study is divided into two parts:The first part concerns the analysis of flow structures of single-phase flows using numerical simulations, which are validated using the results of the experimental campaign. The analysis of the simulations results, from a flow characteristic observable that has been carefully chosen, has allowed quantifying the main flow categories as a function of the heat exchanger geometric parameters and the flow characteristics. This new information on the flow structures has led to the proposal of an original generalized model of the friction law inside this type of heat exchanger with complex geometry.The second part concerns the study of condensation with and without vapor superheating at the inlet of the heat exchanger. Thus, a specific experimental setup allowing precise control of the boundary conditions has been developed. Otherwise a specific metrology, based on infrared thermography, has been set to the point in order to determine the variation of certain local quantities along the condenser (vapor mass fraction, heat transfer coefficient...). Thus, we observe a high and wide variability of the heat transfer coefficients and the heat flux density along the condenser, and the superheating of the vapor tends to increase the heat transfers. These additional measures question certain assumptions of the literature regarding the development of heat transfer correlations in plate heat condensers.

A bord des véhicules électriques (VE) et Hybrides (VEH), les fonctions de tractions sont assurées par des convertisseurs électroniques de puissances. Ces derniers sont constitués de module de puissance (IGBTs ou MOSFETs). Au cours de leur fonctionnement, ces modules sont parfois soumis à de fortes contraintes électriques et thermiques qui amènent à une défaillance ou même à une destruction. Le premier objectif sera de réaliser un banc expérimentale permettant d’étudier le vieillissement des modules IGBTs en régîmes extrêmes de fonctionnement (mode de court-circuit). Ainsi, nous évaluerons les différents indicateurs de vieillissements permettant de prédire la défaillance du composant. Il sera question aussi de suivre le vieillissement ou une dégradation initié sur les composants IGBTs par thermographie infrarouge. Le second objectif sera de modéliser et simuler par éléments finis différentes structures d’IGBTs, afin de valider les modèles en fonctionnement statique et dynamique. L’avantage de l’approche multicellulaire par rapport à l’approche unicellulaire sera mis en avant. / On board electric vehicles (EVs) and hybrid (HEV), the functions of traction is provided by power electronic converters. These consist of power modules (IGBT or MOSFET). During their operation, these modules are sometimes subjected to high electrical and thermal stresses that lead to failure or even destruction.The first objective will be to achieve experimental bench to study ageing IGBT modules under extreme operating conditions ( short circuit mode). Thus, we evaluate the various indicators of ageing to predict component failure. Topics will also follow the ageing or degradation initiated on IGBT components by infrared thermography. The second objective is to model and simulate by finite element different IGBT structures to validate the models in static and dynamic operation. The advantage of multicellular approach to the single cell approach will be highlighted.

Cette étude présente la caractérisation du comportement mécanique et la tenue en fatigue d’un composite thermoplastique à matrice PEEK renforcée en fibres de carbone courtes pour des applications aéronautiques. La première partie présente la description des matériaux étudiés ainsi que la mise en place d’un protocole de caractérisation de la microstructure. Il est alors mis en avant la nécessité de générer des éprouvettes de caractérisation simples en introduisant le concept d’éprouvettes amincies. Dans un second temps, la méthode d’auto-échauffement en régime transitoire est appliquée en concluant sur l’influence de différents paramètres sur le bilan énergétique tels que la microstructure ou le grade du matériau étudié. La troisième partie présente l’établissement d’une loi de comportement phénoménologique avec une prise en compte locale de l’anisotropie par des approches micromécaniques classiques. Les simulations mécanique et énergétique donnent des résultats corrélant très bien avec l’expérimentale pour une distribution d’orientation proche de 0° et des résultats moins convaincants pour une distribution d’orientation proche de 90°. La dernière partie présente l’utilisation d’un protocole de caractérisation rapide basé sur les essais d’auto-échauffement. Cette approche, validée pour les différents matériaux étudiés, permet de prédire la courbe d’endurance en fatigue déterministe avec une seule éprouvette et en une demi-journée d’essais. Il est également mis en évidence qu’un critère énergétique à deux paramètres est indépendant de la distribution d’orientation, et qu’il est possible de discriminer rapidement en fatigue les différents matériaux étudiés. / This study deals with characterization of the mechanical behavior and the fatigue lifetime of a short carbon fibers reinforced PEEKmatrix thermoplastic composite. The first part presents the description of the materials studied and the implementation of the characterization of the microstructure. It’s then emphasized the need to generate simple characterization samples by introducing the concept of thin specimens. In a second step, the heat build-up protocol is applied on the studied materials. It is then highligthed the influence on the energetic assessment of various parameters as the microstructure or the choice of material. The third part presents the etablishment of a phenomenological law of behavior with a local consideration of anisotropy using conventional micromechanical approaches. The mechanical and energetic simulations give resultats correlating very well with the experimental ones for a distribution of orientation close to 0°. The last part presents the use of the heat build-up technique to predict the fatigue lifetime. This approach uses an energetic criterion with two parameters and is able to predict the deterministic fatigue curve with one sample, in half a day. It is then shown the capability to catch the influence of the variations of matrix grade and fibers content on the fatigue properties and validates the use of the technique for fastmaterials screening.