Cette synthèse porte sur plusieurs thématiques de mécanique des fluides et s'articule autour d'une approche par des méthodes expérimentales instationnaires. Les domaines successivement abordés sont la turbulence, l'aérodynamique compressible, les machines tournantes, l'hydrodynamique et les instabilités, tandis que les techniques expérimentales mises en œuvre comprennent les sondes directionnelles de pression, l'anémométrie fil/film chaud, la vélocimétrie laser Doppler, la visualisation par injection de traceur et la vélocimétrie par images de particules. Dans la plupart des cas, on développe des techniques multi-composantes, afin d'obtenir les trois composantes du champ de vitesse. Lorsqu'un phénomène périodique est présent dans l'écoulement, des traitements par moyennes de phase permettent de reconstruire, à partir d'un maillage de mesures ponctuelles, une information globale dans un plan ou dans un volume, et son évolution temporelle moyenne. Il est aussi possible de reconstituer une dynamique en fonction du temps à partir d'une mesure dans un plan, non résolue en temps, synchronisée avec une mesure ponctuelle, résolue en temps. L'ensemble des configurations étudiées par ces méthodes expérimentales constitue des bases de données, utiles notamment pour une comparaison avec des résultats de simulations numériques.

La réduction de la consommation des bâtiments passe par : l'économie d'énergie, l'efficacité énergétique et l'utilisation des énergies renouvelables. Sur ce dernier point, l'intégration à grande échelle de composants photovoltaïques (PV) est une solution. Le rendement et la durée de vie des cellules PV en silicium cristalin diminuant avec l'augmentation de leur température de fonctionnement, il est essentiel de mettre au point des configurations d'intégration limitant leur échauffement. L'intégration en configuration de double-peau - la surface PV est séparée du bâtiment par une lame d'air - est une solution prometteuse. Sous l'effet de la chaleur, un écoulement de convection naturelle se met en place entre les deux parois, refroidissant ainsi les panneaux PV. Cet écoulement peut également servir de moteur pour la ventilation en été, et de préchauffage de l'air en hiver. Cette étude, expérimentale, fait partie d'un projet visant à comprendre le fonctionnement des double-peaux PV en analysant séparément les différents phénomènes physiques avant de prendre en compte l'ensemble des couplages. Elle porte plus particulièrement sur la convection naturelle au sein des double-façades verticales. Ici, la double-peau est modélisée par un canal vertical dont les deux parois principales sont chauffées sous des conditions de flux imposé. Un banc d'essais a été développé pour étudier la convection naturelle dans un canal vertical en eau. L'eau a été choisie pour se placer dans le cas d'un écoulement de convection pure (pas de rayonnement entre les parois). C'est un canal vertical de 65 cm de haut avec un écartement réglable placé dans une cuve de 1,5 m de haut contenant 160 L d'eau. Les parois sont chauffées à l'aide de 24 chaufferettes indépendantes délivrant un flux de chaleur uniforme, ce qui permet d'appliquer différentes configurations de chauffage. Des mesures de flux et de température sont réalisées au niveau des parois, et un système couplant de la velocimétrie laser Doppler deux composantes à un micro-thermocouple (25 μm) a été développé pour avoir accès aux vitesses verticale et horizontale et à la température dans le canal. Ce banc et son instrumentation sont décrits et les incertitudes de mesure associées ont été caractérisées. La configuration de chauffage uniforme symétrique a été étudiée ici pour différentes puissances injectées. Les profils de vitesse et de température moyennes mettent en évidence la présence d'un changement de régime d'écoulement dans le canal pour un nombre de Rayleigh indéntifié. L'étude approfondie des profils des fluctuations de vitesse et de température a permis de mettre au point une modélisation comportementale de ce changement de régime. De plus, une première approche est développée pour évaluer la pression dans le canal à partir de l'analyse et de l'estimation des différents termes de l'équation de conservation de la quantité de mouvement.

Unconfined multiple interacting confluent round jets are interesting from a purely scientific point of view, as interaction between neighboring jets brings additional complexity to the flow field. Unconfined confluent round jets also exist in various engineering applications, such as ventilation supply devices, sewage disposal systems, combustion burners, chemical mixing or chimney stacks. Even so, little scientific attention has been paid to unconfined confluent round jets. The present work uses both advanced measurement techniques and computational models to provide deeper understanding of the turbulent flow field development of unconfined confluent round jets. Both Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) have been used to measure mean velocity and turbulence properties within two setups, consisting of a single row of 1×6 jets and a square array of 6×6 confluent jets. Simulations using computational fluid dynamics (CFD) of the 6×6 setup were conducted using three different Reynolds Averaged Navier-Stokes (RANS) turbulence models: the standard k-ε, the RNG k-ε and the Reynolds Stress model (RSM). The results from the CFD simulations were compared with experimental data. The employed RANS turbulence models were all capable of accurately predicting mean velocities and turbulent properties in the investigated confluent jet array. In general the RSM and k-ε std. models provided smaller deviations between numerical and experimental results than the RNG k-ε model. In terms of mean velocity the second-order closure model (RSM) was not found to be superior to the less complex standard k-ε model. The validated CFD model was employed in a parametrical investigation, including five independent variables: inlet velocity, nozzle diameter, nozzle edge-to-edge spacing, nozzle height and the number of jets in the array. The parametrical investigations made use of statistical methods in the form of response surface methodology. The derived response surface models provided information on the principal influence and relative importance of the investigated parameters within the investigated design space. The positions of the jets within the array strongly influence both mean velocity and turbulence. In all investigated setups the jets experience merging and combining. Square arrays also include considerable jet convergence, which was not present in the 1×6 jet array. Due to the jet convergence in square arrays the turbulent flow field, especially for jets far away from the array center, is affected by mean flow curvature. Jets located along the sides of square jet arrays experience strong jet-to-jet interactions that result in considerable jet deformation, shorter potential core, higher turbulent kinetic energy and faster velocity decay compared to other jets. Jets located at the corners of the array do not interact as strongly with neighboring jets as do the jets along the sides. The locations of merging and combined points differ considerably between different jets and different jet configurations. As the jets combine a zone with uniform stream-wise velocity and low turbulence intensity forms in the center of square jet arrays. This zone has been called Confluent Core Zone (CCZ) due to its similarities with the potential core zone of a single jet. Within the CCZ the appropriate scaling length changes from nozzle diameter to the effective source diameter. The parametrical investigation showed that nozzle diameter and edge-to-edge nozzle spacing were the most important of the investigated parameters, reflecting a strong dependence on dimensionless jet spacing, S/d0. Higher S/d0 delays both merging and combining of the jets and leads to a CCZ with lower velocity and longer downstream extension. Increasing the array size leads to a reduced combined point distance, a stronger inwards displacement of jets in the outer part of the array, and reduced entrainment near the nozzles. A higher inlet velocity was found to increase the jet convergence in the investigated square confluent jet arrays. Nozzle height generally has minor impact on the investigated response variables.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A hanseníase é uma doença infecciosa com características únicas, dentre elas o fato de atingir intensamente a inervação da pele e seus anexos. Entremeando estes anexos, está a microcirculação cutânea, que a principio também tem sua inervação comprometida. Vários artigos apontam para alterações de disautonomia microcirculatória, citando como exemplo as alterações no reflexo vasomotor. O presente estudo se propõe a avaliar a microcirculação cutânea na hanseníase virchowiana, tanto em sua morfologia quanto em sua reatividade vascular. Para isto, utilizamos a tecnologia de luz ortogonal polarizada através do equipamento Cytoscan, a analise de Fourier do sinal do laser Doppler para estudo da vasomotricidade e o laser Doppler fluxometria associado à iontoforese de substâncias vasoativas (acetilcolina, nitroprussiato de sódio e noradrenalina) para avaliação da reatividade vascular. Dez pacientes portadores de hanseníase virchowiana sem outras comorbidades que pudessem alterar os parâmetros microcirculatórios, foram avaliados pelos métodos descritos e seus resultados foram comparados aos de dez controles sem hanseníase ou qualquer outra comorbidade. Em relação à vasomotricidade não foram observadas alterações estatisticamente significativas entre os grupos, o que fala a favor da teoria de origem miogênica para a vasomotricidade. Em relação à iontoforese de substâncias vasoativas constatou-se uma diminuição da resposta vasodilatadora à acetilcolina e ao nitroprussiato nos pacientes com hanseníase. Os exames com o Cytoscan mostraram aumento no tamanho dos capilares, bem como alterações em sua morfologia. Os resultados apresentados sugerem que, provavelmente devido ao longo período de alteração inervatória decorrente da hanseníase virchowiana, estes pacientes apresentam uma alteração significativa tanto morfológica quanto na reatividade vascular da microcirculação cutânea. / Leprosy is an infectious disease with unique characteristics. One of them is the fact that it compromises not only the cutaneous and adnexial innervation, but also the innervation of the cutaneous microcirculation. Several articles indicate the impact of disautonomy on the microcirculatory level, citing the example of changes in vasomotor level. The present study proposes to evaluate morphology and microvascular reactivity of the cutaneous microcirculation of the virchowian leprosy. Methods employed in the study were: the Cytoscan, which uses the orthogonal polarized light, the Fourier analysis of the laser Doppler signal to study vasomotion, and the laser Doppler flowmetry associated with iontophoresis of vasoactive substances (acetylcholine, sodium nitroprusside and norepinephrin). Ten patients with virchowian leprosy, without any other comorbidity that could modify the microvascular parameters were evaluated and their results were compared to ten controls without leprosy or any other comorbidity. Regarding the vasomotion, no statistical significant differences were noticed between the groups. Our data are in agreement with the vasomotions miogenic origin theory. According to iontophoresis of vasoactive substances, it was found that there is a reduced endothelial-dependent and endothelial-independent vasodilation in patients with leprosy while tests by direct visualization we observed an increase in the size of capillaries, as well as changes in their morphology. The results suggest that the significant changes in morphology and vascular reactivity of skin microcirculation are probably due to the long period of innervatory changes arising from leprosy.

The production from an oil reservoir is a mixture of liquids (oil and water) and gas, and is often maintained by using a pump placed in the well to ensure a continuous flow to the surface. Electrical Submersible Pumps consist of stacked centrifugal pump stages, each comprising a bladed impeller (rotating part) and diffuser (stationary part). In multiphase conditions, the gas tends to accumulate in the impeller, severely reducing the pressure produced by the pump. Radial-flow pumps operate in a plane perpendicular to their rotation axis, while mixed-flow pumps are characterised by a lower meridional angle (generally 40 to 80 degrees), and are generally better at handling gas-liquid mixtures. We first describe the impact of gas on the whole pumping system, from the reservoir to the storage facility, and give context to the subject. The available literature shows that the size of the gas bubbles present in the fluid is critical to the pump performance. A transparent, full-scale pump was built in order to explore the flow features in single and multiphase flows. Laser Doppler Velocimetry and high speed imaging in single phase flow showed a high turbulence level in the wake of the impeller blades, and recirculation cells at low flow rates. In gas-liquid conditions, we demonstrated that the bubble size varies within a pump stage, as break-up occurs at the impeller tip, and coalescence is dominant in the diffuser, especially because of recirculation. The first impeller acted as a mixer, and at moderate to high gas fractions (10 to 30%), the flow patterns at the stage level alternated between bubbly and radially separated flows. Finally, a dispersed-gas model was developed to predict the pressure rise in a mixed-flow pump impeller under gas-liquid conditions. This model based on the forces acting on a single spherical gas bubble, was implemented with a simplified, parametric representation of the flow field in a mixed-flow impeller. In the meridional direction, the Coriolis force opposes the centrifugal force and the adverse pressure gradient. Both forces tend to retain the gas bubble within the impeller. The relative magnitude of the drag force strongly depends on the maximal bubble diameter, which was determined as a function of the flow conditions and used to calculate the gas velocity through the impeller. This method resulted in a better agreement with the experimental data than a one-dimensional two-fluid model where the gas phase follows the same path as the liquid. We used the dispersed-gas model to give quantitative evidence that low blade and meridional angles reduce the gas accumulation and the associated performance degradation.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A hanseníase é uma doença infecciosa com características únicas, dentre elas o fato de atingir intensamente a inervação da pele e seus anexos. Entremeando estes anexos, está a microcirculação cutânea, que a principio também tem sua inervação comprometida. Vários artigos apontam para alterações de disautonomia microcirculatória, citando como exemplo as alterações no reflexo vasomotor. O presente estudo se propõe a avaliar a microcirculação cutânea na hanseníase virchowiana, tanto em sua morfologia quanto em sua reatividade vascular. Para isto, utilizamos a tecnologia de luz ortogonal polarizada através do equipamento Cytoscan, a analise de Fourier do sinal do laser Doppler para estudo da vasomotricidade e o laser Doppler fluxometria associado à iontoforese de substâncias vasoativas (acetilcolina, nitroprussiato de sódio e noradrenalina) para avaliação da reatividade vascular. Dez pacientes portadores de hanseníase virchowiana sem outras comorbidades que pudessem alterar os parâmetros microcirculatórios, foram avaliados pelos métodos descritos e seus resultados foram comparados aos de dez controles sem hanseníase ou qualquer outra comorbidade. Em relação à vasomotricidade não foram observadas alterações estatisticamente significativas entre os grupos, o que fala a favor da teoria de origem miogênica para a vasomotricidade. Em relação à iontoforese de substâncias vasoativas constatou-se uma diminuição da resposta vasodilatadora à acetilcolina e ao nitroprussiato nos pacientes com hanseníase. Os exames com o Cytoscan mostraram aumento no tamanho dos capilares, bem como alterações em sua morfologia. Os resultados apresentados sugerem que, provavelmente devido ao longo período de alteração inervatória decorrente da hanseníase virchowiana, estes pacientes apresentam uma alteração significativa tanto morfológica quanto na reatividade vascular da microcirculação cutânea. / Leprosy is an infectious disease with unique characteristics. One of them is the fact that it compromises not only the cutaneous and adnexial innervation, but also the innervation of the cutaneous microcirculation. Several articles indicate the impact of disautonomy on the microcirculatory level, citing the example of changes in vasomotor level. The present study proposes to evaluate morphology and microvascular reactivity of the cutaneous microcirculation of the virchowian leprosy. Methods employed in the study were: the Cytoscan, which uses the orthogonal polarized light, the Fourier analysis of the laser Doppler signal to study vasomotion, and the laser Doppler flowmetry associated with iontophoresis of vasoactive substances (acetylcholine, sodium nitroprusside and norepinephrin). Ten patients with virchowian leprosy, without any other comorbidity that could modify the microvascular parameters were evaluated and their results were compared to ten controls without leprosy or any other comorbidity. Regarding the vasomotion, no statistical significant differences were noticed between the groups. Our data are in agreement with the vasomotions miogenic origin theory. According to iontophoresis of vasoactive substances, it was found that there is a reduced endothelial-dependent and endothelial-independent vasodilation in patients with leprosy while tests by direct visualization we observed an increase in the size of capillaries, as well as changes in their morphology. The results suggest that the significant changes in morphology and vascular reactivity of skin microcirculation are probably due to the long period of innervatory changes arising from leprosy.

The principle of controlled auto-ignition (CAI) is to mix fuel and air homogeneously before compressing the mixture to the point of auto-ignition. As ignition occurs simultaneously, CAI engines operate with lean mixtures preventing high cylinder pressures. CAI engines produce small amounts of nitrogen oxides (NOx) due to low combustion temperatures while maintaining high compression ratios and engine efficiencies. Due to simultaneous combustion and lean mixtures, CAI engines are restricted between low and mid load operations. Various strategies have been studied to improve the load limit of CAI engines. The scope of the project is to investigate the consequences of varying valve timing, as a method to control the mixture temperature within the combustion chamber and therefore, controlling the mixture auto-ignition point. This study presents computational fluid dynamics (CFD) modelling results of transient flow, inside a 0.45 litre Lotus single cylinder engine. After a validation process, a chemical kinetics model is combined with the CFD code, in order to study in-cylinder temperatures, the mixture distribution during compression and to predict the auto-ignition timing. The first part of the study focuses on validating the calculated in-cylinder velocities. A mesh sensitivity study is performed as well as a comparison of different turbulence models. A method to reduce computational time of the calculations is presented. The effects of engine speed on charge delay and charge amount inside the cylinder, the development of the in-cylinder flow field and the variation of turbulence parameters during the intake and compression stroke, are studied. The second part of the study focuses on the gasoline mixture and the variation of the valve timing, to retain different ratios of residual gases within the cylinder. After validation of the model, a final set of CFD calculations is performed, to investigate the effects of valve timing on flow and the engine parameters. The results are then compared to a fully homogeneous mixture model to study the benefits of varying valve duration. New key findings and contributions to CAI knowledge were found in this investigation. Reducing the intake and exhaust valve durations created a mixture temperature stratification and a fuel concentration distribution, prior to auto-ignition. It resulted in extending the heat release rate duration, improving combustion. However, shorter valve timing durations also showed an increase in heat transfer, pumping work and friction power, with a decrease of cylinder indicated efficiency. Valve timing, as a method to control auto-ignition, should only be used when the load limit of CAI engines, is to be improved.

La réduction de la consommation des bâtiments passe par : l'économie d'énergie, l'efficacité énergétique et l'utilisation des énergies renouvelables. Sur ce dernier point, l'intégration à grande échelle de composants photovoltaïques (PV) est une solution. Le rendement et la durée de vie des cellules PV en silicium cristalin diminuant avec l'augmentation de leur température de fonctionnement, il est essentiel de mettre au point des configurations d'intégration limitant leur échauffement. L'intégration en configuration de double-peau – la surface PV est séparée du bâtiment par une lame d'air – est une solution prometteuse. Sous l'effet de la chaleur, un écoulement de convection naturelle se met en place entre les deux parois, refroidissant ainsi les panneaux PV. Cet écoulement peut également servir de moteur pour la ventilation en été, et de préchauffage de l'air en hiver. Cette étude, expérimentale, fait partie d'un projet visant à comprendre le fonctionnement des double-peaux PV en analysant séparément les différents phénomènes physiques avant de prendre en compte l'ensemble des couplages. Elle porte plus particulièrement sur la convection naturelle au sein des double-façades verticales. Ici, la double-peau est modélisée par un canal vertical dont les deux parois principales sont chauffées sous des conditions de flux imposé. Un banc d'essais a été développé pour étudier la convection naturelle dans un canal vertical en eau. L'eau a été choisie pour se placer dans le cas d'un écoulement de convection pure (pas de rayonnement entre les parois). C'est un canal vertical de 65 cm de haut avec un écartement réglable placé dans une cuve de 1,5 m de haut contenant 160 L d'eau. Les parois sont chauffées à l'aide de 24 chaufferettes indépendantes délivrant un flux de chaleur uniforme, ce qui permet d'appliquer différentes configurations de chauffage. Des mesures de flux et de température sont réalisées au niveau des parois, et un système couplant de la velocimétrie laser Doppler deux composantes à un micro-thermocouple (25 μm) a été développé pour avoir accès aux vitesses verticale et horizontale et à la température dans le canal. Ce banc et son instrumentation sont décrits et les incertitudes de mesure associées ont été caractérisées. La configuration de chauffage uniforme symétrique a été étudiée ici pour différentes puissances injectées. Les profils de vitesse et de température moyennes mettent en évidence la présence d'un changement de régime d'écoulement dans le canal pour un nombre de Rayleigh indéntifié. L'étude approfondie des profils des fluctuations de vitesse et de température a permis de mettre au point une modélisation comportementale de ce changement de régime. De plus, une première approche est développée pour évaluer la pression dans le canal à partir de l'analyse et de l'estimation des différents termes de l'équation de conservation de la quantité de mouvement. / Reducing the building consumption passes through : energy saving, energy efficiency and the use of renewable energy sources for a local production of electricity. For the last point, the building integrated photovoltaic systems represent a promising solution. However, electrical yield and life time of silicon solar cells decrease with the increase of its operating temperature, that is why integrated configurations which limits cell overheating must be developed. The solution considered is the double-skin façade configuration : photovoltaic panels are separated from the building wall(or roof) by an opened air channel. This induces a natural convection flow that cools the rear surface of the photovoltaic panels. This flow can also be used for natural ventilation of buildings in summer or for air preheating in winter. This experimental study is part of a project on photovoltaic double-skin façades. In this project, each physical phenomena are analysed separately first, and the coupling between the different phenomena are studied in a second time. This thesis deals with the natural convection into the vertical double-skin façades. The system is modelled by a vertical channel with isoflux heating at the two mains walls. An experimental apparatus was developed in the laboratory for studying natural convection in water in a vertical channel. Water is used as the working fluid to avoid radiative heat transfer and obtain a pure convective flow. The channel is 65 cm high with an adjustable gap. It is placed in a 1.5 m high glass tank filled with 160 L of distilled water. The main walls are heated through 24 independant electrical heaters maintaining a constant heat flux, which allows differents boundary condition (symmetrical, asymmetrical, uniforme, alternated, etc). Heat flux and temperature measurements are made at the walls. The velocity (horizontal and vertical) and temperature of the flow are measured through a two components Laser Doppler Velocimetry system combined with a micro-thermocouple (25 μm diameter). This apparatus is described in details and the measurement uncertainties were characterized. The symmetrical uniform heating configuration was studied here with the analyse of velocity and temperature profiles in the channel for several input power (46 W to 562 W). These profiles show a change in flow regime in the channel that is analysed with turbulent quantities along the channel. Moreover, the pressure is estimated in the channel from the analysis of all the terms of the momentum conservation equations.

The development of a Doppler Global Veocimetry (DGV) system is described. An argon ion laser has been modified to suit the requirements of DGV. An etalon with high precision tilting control has been mounted in the laser cavity. The backward mirror of the laser cavity has been mounted on a piezotranslator for controlling the laser cavity length. Two iodine cells have been designed and manufactured: one with a bead of iodine in the cell volume, the other with a limited amount of iodine. The iodine absorption line of both cells has been calibrated with good repeatibility. The laser has been stabilized in frequency, so that operations during a measurement session in the lab are simplified. The capabilities of DGV measurements have been tested in two jets, at low and at high speeds. Velocity fluctuations of the jet could be followed, in spite of the highly noisy signals. The first steps towards three velocity component measurements with a single camera in a difficult environment such as the geometry of a turbomchinery cascade have been made. Imaging two views of a target on the same camera sensor is discussed, along with the spatial and luminosity calibration required. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

La surdité est un problème de santé publique. Le vieillissement de la population explique ainsi une grande partie des causes de surdités, par la fréquence de la presbyacousie. Le principal moyen de la réhabilitation auditive est représenté par les prothèses auditives conventionnelles. Les aides auditives ont considérablement progressé ces dernières années, principalement en termes d’amélioration du traitement du signal. Ceci étant dit, outre le problème économique, certains facteurs limitent encore les bénéfices que les patients peuvent ressentir (occlusion du conduit auditif, effet larsen, absence d’amplification en ambiance sonore,…). Les implants d’oreille moyenne sont destinés à amplifier le signal sonore en le transmettant à l’oreille moyenne pour compenser une perte auditive. Ils sont indiqués en cas d’échec ou de contre-indication de l’appareillage conventionnel. Cependant, les implants d’oreille moyenne présentent certaines limites comme l’insuffisance de performance. Des données récentes montrent que les performances des techniques de réparation de la chaîne ossiculaire sont dépendantes du couplage des prothèses ossiculaires à la chaîne des osselets. Par ailleurs, des avancées dans la compréhension de la biomécanique de la chaîne ossiculaire confirment l’importance du placement et du couplage des procédés de restauration chirurgicaux. Nous avons formulé l’hypothèse selon laquelle ces données pouvaient être appliquées aux implants d’oreille moyenne pour en améliorer les performances. Nous avons voulu analyser expérimentalement les effets sur les performances de variables telles que : placement d’un transducteur, le couplage à la chaîne des osselets, la taille de l’effecteur, l’effet de stimulations alternatives. Nous avons utilisé un transducteur électromagnétique de dernière génération (Otologics MET-V Gen 2) et une technique d’analyse de la vibration des structures de l’oreille moyenne par vélocimétrie laser. Les résultats ont montré une nette amélioration des performances en fonction des modifications de placement et de couplage à la chaîne des osselets ou à la fenêtre ronde. / Hearing loss is a public health issue. Ageing is the most frequent cause of deafness. The main option for the rehabilitation of hearing loss is the use of conventional hearing aids. These aids have dramatically improved their performance for the past 20 years, mostly with regards to signal processing. However, in addition to economic reasons, some limitations remain (occlusion, feedback, hearing in noise…) and limit the satisfaction of patients. Active middle ear implants (AMEI) have been developed to overcome some of these problems and are indicated n conventional hearing failed to improve patients’ quality of hearing. However, AMEI suffer from limitations, as insufficient performances for severe hearing losses. Recent experimental and clinical data have highlighted the importance of coupling and placement of ossicular reconstruction passive prosthesis use. Other reported new findings regarding the biomechanism of the ossicular chain, especially for high frequency hearing, which is, unfortunately, where most people have their hearing loss. We hypothesized that these findings could be applied to AMEI use. We have analysed experimentally the effects on AMEI performance of variables such as: placement, coupling, size of tranduscer vibrating tip, alternative stimulation options. We used a electromagnetic tranducer from Otologics LLC to drive the middle ear or round window membrane, and a laser Doppler vibrometer to assess for the induced middle transfer function. Results have shown that we could provide great improvement in performance when varying the coupling method and the placement to the ossicular chain or the round window membrane.