L'intérêt croissant susciter par les applications biomédicales des plasmas non thermiques, inspire le développement de nouvelles sources plasmas. Les décharges à barrière diélectrique (DBD) ou les décharges couronne générées dans l'air ambiant ou dans le flux de gaz rare sont généralement utilisées. Production des plasmas directement dans un liquide a un grand potentiel pour les processus de stérilisation des substances liquides et pour le traitement extracorporel du sang. Les mécanismes physiques de formation d’une décharge électrique dans un milieu liquide ne sont toujours pas entièrement compris .La première partie de cette thèse examine le sujet de l'initiation et le développement de décharge nanoseconde dans les diélectriques liquides (eau déminéralisée, éthanol et n-pentane). La visualisation ombroscopique résolue en temps, la spectroscopie optique d'émission et les mesures électrique sont appliqués à l’étude d’une décharge électrique initiée sur une électrode à pointe positive.Nous avons montré que, selon l'amplitude de tension trois scénarios différents peuvent se produire dans des diélectriques polaires, notamment, la cavitation d'une bulle, le développement de décharge dans une cavité gazeuse (le mode ‘buisson’) et l'initiation de la décharge filamentaire (le mode ‘arborescent’) se propageant directement dans le liquide. La différence dans la formation et la propagation de deux modes de la décharge (‘buisson’ et ‘arbre’) révèle les mécanismes physiques étant très distincts.Dans la deuxième partie de ce travail, nous abordons la question d’interaction entre les plasmas froids atmosphériques avec les cellules vivantes in vitro et in vivo. L’étude porte sur le mécanisme de la mort cellulaire induite par le plasma. Cytométrie de flux avec deux marqueurs AnnexinV (AV) et de l'iodure de propidium (PI) a été appliquée pour l’analyse de la viabilité cellulaire. On montre l’induction de l' apoptose dans les cellules de T lymphocyte humain (Jurkat) et dans les cellules épithéliales (HMEC) traités par le plasma de DBD nanoseconde. Dans les souris nudes l'induction de l'apoptose et de la nécrose en fonction de la dose est observé par la microscopie électronique dans les coupes de l'épiderme. L'analyse histologique montre l’apparition des lésions importantes dans l'épiderme , derme, hypoderme et les muscles en fonction de la durée du traitement. Production de peroxyde d'hydrogène dans le milieu de culture (PBS) exposé au plasma de DBD est mesurée à l’aide d’une sonde fluorescente sélective (Amplex® Red). La viabilité des cellules de la thyroïde humaines ( HTori -3) et des cellules de mélanome (1205Lu) cellules démontre la dépendance nonmonotone de la concentration de H2O2. Le rôle majeur du peroxyde d'hydrogène produit par plasma et du champ électrique de la DBD est suggéré. / Growing interest in biomedical applications of nonthermal plasmas inspires the development of new plasmas sources. Dielectric barrier (DBD) and corona discharges produced in ambient air or in noble gas flow are typically applied. Direct production of plasma in liquids has a great potential for sterilization of liquid substances and extracorporeal blood treatment. The physical mechanisms of discharge formation in liquid medium are not fully understood.The first part of this thesis deals with the initiation and development of the nanosecond discharge in liquid dielectrics (deionized water, ethanol and n-pentane). Time-resolved shadowgraph visualization, optical emission spectroscopy and electrical diagnostics are applied to investigate the discharge formation on point anode.We have shown that depending on the applied voltage amplitude three different scenario can occur in the polar dielectric, namely, cavitation of a bubble, discharge development in the gaseous cavity (bush-like mode) and initiation of the filamentary discharge (tree-like mode) propagating in bulk liquid. Formation of the bush-like and the tree-like discharges is governed by distinct physical mechanisms, resulting in strongly different plasma parameters.In the second part of this work we address the question of how cold atmospheric plasma interacts with living cells in-vitro and in-vivo, and what is the mechanism of plasma induced cell death. Flowcytometry based cell viability assay with two markers AnnexinV (AV) and Propidium iodide (PI), demonstrates a dose dependent induction of the apoptosis for human T lymphocyte (Jurkat) and epithelial (HMEC) cells treated with DBD plasma. In nude mice model, induction of apoptosis and necrosis in dose dependant manner is observed by electron microscopy in thin epidermis sections. Histological analysis shows significant lesions appeared in epidermis, dermis, hypodermis and muscle as a function of treatment duration. Production of hydrogen peroxide in culture medium (PBS) exposed to DBD plasma is measured using selective fluorescent probe (Amplex® Red). Cell viability of human thyroid epithelial (HTori-3) and melanoma (1205Lu) cells demonstrates nonmonotonous dependence on H2O2 concentration. The major role of plasma produced hydrogen peroxide and DBD electric field is suggested.

The coronal mass ejections (CMEs) are phenomena that evidence the complex solar activity. During the CME evolution in the solar wind (SW) the shock and sheath (Sh) are established. With these, the transfer of energy and shock thermalization have origin through several processes like instabilities and particle acceleration. Here, we present two studies related to CMEs. In the first study, we analyze the existence of the KelvinHelmholtz instability (KHI) at the interfaces CMESh and ShSW. For this purpose, we assumed two CMEs that propagate independently in the slow and fast SW. We model velocities, densities and magnetic field strengths of sheaths, and SW in the CMEs flanks, in order to solve the Chandrasekhar condition for the magnetic KHI existence. Our results reveal that KHI formation is more probably in the CME that propagate in the slow SW than in CME propagating in the fast SW. It is due to large shear flow between the CME and the slow SW. Besides we find that the interface ShSW is more susceptible to the instability. In the second study, we examine the distributions of particle acceleration and turbulence regions around CME-driven shocks with wave-like features. We consider these corrugated shock as the result of disturbances from the bimodal SW, CME deflection, irregular CME expansion, and the ubiquitous fluctuations in the solar corona. We model smooth CME-driven shocks using polar Gaussian profiles. With the addition of wave-like functions, we obtain the corrugated shocks. For both shock types are calculated the shock normal angles between the shock normal and the radial upstream coronal magnetic field in order to classify the quasi-parallel and quasi-perpendicular regions linked to the particle acceleration and turbulence regions, respectively. Our calculations show the predisposition of the shock to the particle acceleration and indicate that the irregular CME expansion is the relevant factor in the particle acceleration process. We consider that these wave-like features in shocks may be essential in the study of current problems as injection particle, instabilities, downstream-jets, and shock thermalization. / As ejeções de massa coronal (do inglês coronal mass ejections, CMEs) são consideradas traçadores da atividade solar. Durante a evolução das CMEs no vento solar (do inglês solar wind, SW), o choque e o envoltório (do inglês sheath, Sh) são estabelecidos. Nesta fase, a transferência da energia e a termalização do choque podem ter origem através de vários processos, entre eles instabilidades e aceleração de partculas. Aqui nós apresentamos dois estudos relacionados às CMEs. No primeiro estudo, analisamos a existência da instabilidade KelvinHelmholtz (KHI) nas interfaces CMESh e ShSW. Para isto, supomos duas CMEs que se propagam independentemente no SW lento e rápido. Modelamos as velocidades, densidades e a intensidade do campo magnético dos envoltórios e SW nos flancos das CMEs, a fim de resolver a condição de Chandrasekhar para a existência da KHI magnética. Nossos resultados revelam que a formação da KHI pode ser mais provável na CME que se propaga no SW lento do que na CME que se propaga no SW rápido. Isto é devido a um maior cisalhamento entre a CME e o SW lento. Além disso, encontramos que a interface ShSW é ser mais suscetvel à instabilidade. No segundo estudo, examinamos as distribuições das regiões de aceleração de partculas e turbulência em choques ondulados com caractersticas semelhantes a ondas. Assumimos choques ondulados como resultado de perturbações do SW bimodal, deflexão da CME, expansão irregular da CME, e flutuações onipresentes na coroa solar. Construmos choques sem ondulações usando perfis Gaussianos. Com adição de funções semelhantes a ondas, obtemos os choques ondulados. Para ambos tipos de choques, calculamos os ângulos entre o vector normal ao choque e o campo magnético coronal radial, assim classificamos as regiões como quase-paralelas e quase-perpendiculares que são ligadas às regiões de aceleração de partculas e turbulência, respectivamente. Nossos cálculos mostram a predisposição do choque para o fenômeno de acceleração de partculas, e indicam que a expansão irregular da CME é o fator de maior relevância neste processo. Consideramos que assumir ondulações nos choques pode ser essencial nos estudos de problemas atuais como injeção de partculas, instabilidades, jatos e termalização dos choques.

Dans des milieux tels que les gaz, les plasmas et les milieux granulaires, un objet se déplaçant à des vitessessupersoniques, compresse et chauffe le fluide devant lui, formant ainsi une onde de choc. La zone hors-équilibreappelée front d’onde, où ont lieu de brusques variations de température, pression et densité, présente unestructure particulière, avec notamment des distributions des vitesses des particules fortement non-gaussienneset difficiles à visualiser. Dans une avancée importante en 1951, Mott-Smith décrit le front d’onde comme lasuperposition des deux états que sont le gaz supersonique initial et le gaz subsonique compressé et chauffé,impliquant ainsi l’existence de distributions des vitesses bimodales. Des expériences à grands nombres de Machont confirmé cette structure globalement bimodale. Ce modèle n’explique cependant pas la présence d’un surplusde particules à des vitesses intermédiaires, entre le gaz supersonique et le gaz subsonique.Ce travail de thèse porte sur l’étude des ondes de choc dans les gaz granulaires, où les particules interagissentuniquement par des collisions binaires inélastiques. Dans ces gaz dissipatifs, la température granulaire, traduisantl’agitation des particules, permet de définir l’équivalent d’une vitesse du son par analogie aux gaz moléculaires.Les basses valeurs de ces vitesses du son dans les gaz granulaires, permettent de générer facilement des ondes dechoc dans lesquelles chaque particule peut être suivie, contrairement aux gaz moléculaires. La première partie decette étude porte sur l’effet de la dissipation d’énergie, due aux collisions inélastiques, sur la structure des ondesde choc dans les gaz granulaires. Les modifications induites sur la température, la densité et la vitesse moyennemesurées, sont interprétées à l’aide d’un modèle basé sur l’hypothèse bimodale de Mott-Smith et intégrant ladissipation d’énergie. La deuxième partie est consacrée à l’interprétation des distributions des vitesses dans lefront d’onde. À partir des expériences réalisées dans les gaz granulaires, une description trimodale, incluant unétat intermédiaire supplémentaire, est proposée et étendue avec succès aux distributions des vitesses dans lesgaz moléculaires. / In different materials such as gases, plasmas and granular material, an object, moving at supersonic speed,compresses and heats the fluid ahead. The shock front is the out-of-equilibrium area, where violent changesin temperature, pressure and density occur. It has a particular structure with notably strongly non-Gaussianparticle velocity distributions, which are difficult to observe. In an important breakthrough in 1951, Mott-Smithdescribes the shock front as a superposition of two states: the initial supersonic gas and the compressed andheated subsonic gas, implying existence of bimodal velocity distributions. Several experiences at high Machnumbers show this overall bimodal structure. However this model does not explain the existence of a surplusof particles with intermediate velocities, between the supersonic and the subsonic gas.This thesis focuses on shock waves in granular gases, where particles undergo only inelastic binary collisions.In these dissipative gases, the granular temperature, reflecting the particle random motion, allows to definethe equivalent to the speed of sound by analogy with molecular gases. The low values of this speed of soundpermit to generate easily shock waves in which each particle can be tracked, unlike molecular gases. The firstpart of this work focuses on the effect of the energy dissipation, due to inelastic collisions, on the shock frontstructure in granular gases. Modifications induced on temperature, density and mean velocity, are captured bya model based on the bimodal hypothesis of Mott-Smith and including energy dissipation. The second part isdevoted to the study of velocity distributions in the shock front. From experiences in granular gases, a trimodaldescription, including an additional intermediate state, is proposed and successfully extended to the velocitydistributions in molecular gases.

INTRODUÇÃO: O tratamento com ondas de choque (TOC) é utilizado para tratar numerosas afecções musculoesqueléticas, incluindo-se as pseudartroses e as tendinopatias. Há poucos estudos bem estruturados sobre a eficácia do TOC no tratamento da síndrome dolorosa miofascial (SDM) e não há ensaio clínico aleatorizado sobre sua utilização no tratamento das SDMs das regiões lombar e glútea. OBJETIVOS: Avaliar a eficácia do TOC no tratamento das SDMs das regiões lombar e glútea. CASUÍSTICA E MÉTODOS: Foi realizado estudo prospectivo, controlado, com amostra aleatória e duplamente encoberto sobre o tratamento de doentes com dor moderada a intensa decorrente de SDM nas regiões lombar e glútea com duração superior a seis meses, submetidos previamente a tratamento padronizado com antidepressivo, analgésico, terapia física e orientações fisioterápicas durante seis semanas. Foram elegíveis 46 doentes que apresentavam dor com intensidade >= 4 de acordo com a EVA dentre os 121 convocados. Durante seis semanas os doentes elegíveis foram submetidos a tratamento farmacológico e fisioterápico padronizado. Sete doentes usufruíram melhora clínica importante e oito abandonaram o estudo, restando 31 doentes que participaram efetivamente do estudo. Após a randomização, 14 doentes foram submetidos a TOC com cabeçote ativo e 17 a TOC com cabeçote placebo. Foram avaliados os aspectos demográficos, a apresentação clínica, a incapacidade funcional, a intensidade e as características da dor até um ano após a realização dos procedimentos destes 31 doentes. As avaliações foram realizadas com uso da Escala Visual Analógica (EVA), Questionário de Incapacidade de Roland-Morris (RDQ), Índice de Incapacidade de Oswestry (ODI), Versão Reduzida do Questionário de Dor McGill (SF-MPQ) e Inventário Diagnóstico da Dor Neuropática 4 (DN4). RESULTADOS: Não houve diferenças estatisticamente significativas entre os grupos quanto às características sociodemográficas dos doentes. Entretanto, a duração das queixas de dor dos doentes do grupo TOC ativo foi significativamente superior (p < 0,05) a dos do grupo TOC placebo. Em relação aos doentes tratados com TOC placebo, os doentes tratados com TOC ativo usufruíram redução estatisticamente significativa da dor de acordo com a EVA na interação grupo versus tempo a partir do momento \"três meses\"; a melhora manteve-se estatisticamente significativa durante um ano (p < 0,001), achado que sugere que o efeito analgésico instala-se em longo prazo e mantém-se prolongadamente. Não ocorreu modificação estatisticamente significativa na interação grupo versus tempo nas pontuações dos questionários RDQ, ODI e SF-MPQ ao longo do tempo nos doentes de ambos grupos. No momento \"12 meses\" ocorreu redução superior a 50% da incapacidade funcional da dor lombar avaliada de acordo com o RDQ em 70,0% dos doentes do grupo TOC ativo e em apenas 14,3% dos doentes tratados com TOC placebo; diferença percentual estatisticamente significativa (p < 0,05). Ocorreu também redução superior a 50% das pontuações do ODI na avaliação realizada no momento \"12 meses\" em 70,0% dos doentes incluídos no grupo TOC ativo e em apenas 14,3% dos doentes do grupo TOC placebo, diferença percentual estatisticamente significativa (p < 0,05). CONCLUSÕES: O tratamento com o TOC ativo dos doentes com SDM nas regiões lombar e glútea proporcionou melhora significativa da dor a partir do momento \"três meses\" até, pelo menos, o momento \"12 meses\" de acompanhamento, achado que sugere que seu efeito analgésico instala-se tardiamente. Adicionalmente, proporcionou melhora da funcionalidade de acordo com o RDQ e ODI na avaliação realizada no momento \"12 meses\" / INTRODUCTION: Extracorporeal shockwave therapy (ESWT) has been used successfully in different musculoskeletal conditions, including pseudarthrosis and tendinopathies. However, there are very few well-structured studies on the efficacy of ESWT in the treatment of myofascial pain syndromes (MPSs) and no randomized clinical trial about the ESWT in the treatment of lumbar and gluteal myofascial pain. OBJECTIVES: To assess the efficacy of ESWT in the treatment of lumbar and gluteal MPSs. MATERIAL AND METHODS: The study was prospective, randomized, double-blind and placebo-controlled. From 121 patients with moderate or severe pain due to MPS in the lumbar and gluteal regions lasting more than six months were enrolled; a total of 46 patients with pain intensity >= 4 according to the VAS were considered eligible. The elected patients were treated with antidepressant, analgesic and physical therapy as a standard protocol during six weeks. Seven patients had significant clinical improvement with the pharmacological and physical therapies and eight dropped out the study. The remainder 31 patients were randomized and 14 underwent active ESWT and 17 underwent placebo ESWT. The demographic aspects, clinical presentations, functional disabilities, severity and characteristics of pain were evaluated previously to the inclusion in the study until the end of the first year after the treatment with active or placebo ESWT. The evaluations were based on the Visual Analogue Scale (VAS), Roland- Morris Disability Questionnaire (RDQ), Oswestry Disability Index (ODI), Short- Form of the McGill Pain Questionnaire (SF-MPQ), and the Neuropathic Pain Diagnostic Questionnaire 4 (DN4). RESULTS: There were no statistical differences between the groups regarding the baseline characteristics of the patients. However, the duration of pain of the patients treated with active ESWT was significantly higher (p < 0,05) than those treated with placebo ESWT. There was no statistically significant variation over time in the RDQ, ODI and SF-MPQ scores between the patients from each group. Patients treated with active ESWT presented a significant reduction of pain severity according to the VAS from the third until the 12nd month of follow-up (p < 0,001), finding indicative that the analgesic effect of the ESWT starts late but remains over time. At the 12nd month of follow-up, 70,0% of the patients treated with active ESWT and just 14.3% of the patients from de placebo ESWT group had more than 50% improvement of the functional disability of the low back pain according to the RDQ, statistically significant difference (p < 0,05). There was also a reduction of more than 50% of ODI scores in the 12th month of follow-up in 70.0% of the patients treated with active ESWT and in only 14.3% of the patients treated with placebo ESWT (p < 0,05). CONCLUSIONS: The active ESWT provided a significant and lasting reduction in pain intensity from the third until the 12th month of follow-up, finding that suggests that its analgesic effect settles late and has long duration. Additionally, it provided improvement of the functionality according to the RDQ and ODI at the 12th month of follow-up

The coronal mass ejections (CMEs) are phenomena that evidence the complex solar activity. During the CME evolution in the solar wind (SW) the shock and sheath (Sh) are established. With these, the transfer of energy and shock thermalization have origin through several processes like instabilities and particle acceleration. Here, we present two studies related to CMEs. In the first study, we analyze the existence of the KelvinHelmholtz instability (KHI) at the interfaces CMESh and ShSW. For this purpose, we assumed two CMEs that propagate independently in the slow and fast SW. We model velocities, densities and magnetic field strengths of sheaths, and SW in the CMEs flanks, in order to solve the Chandrasekhar condition for the magnetic KHI existence. Our results reveal that KHI formation is more probably in the CME that propagate in the slow SW than in CME propagating in the fast SW. It is due to large shear flow between the CME and the slow SW. Besides we find that the interface ShSW is more susceptible to the instability. In the second study, we examine the distributions of particle acceleration and turbulence regions around CME-driven shocks with wave-like features. We consider these corrugated shock as the result of disturbances from the bimodal SW, CME deflection, irregular CME expansion, and the ubiquitous fluctuations in the solar corona. We model smooth CME-driven shocks using polar Gaussian profiles. With the addition of wave-like functions, we obtain the corrugated shocks. For both shock types are calculated the shock normal angles between the shock normal and the radial upstream coronal magnetic field in order to classify the quasi-parallel and quasi-perpendicular regions linked to the particle acceleration and turbulence regions, respectively. Our calculations show the predisposition of the shock to the particle acceleration and indicate that the irregular CME expansion is the relevant factor in the particle acceleration process. We consider that these wave-like features in shocks may be essential in the study of current problems as injection particle, instabilities, downstream-jets, and shock thermalization. / As ejeções de massa coronal (do inglês coronal mass ejections, CMEs) são consideradas traçadores da atividade solar. Durante a evolução das CMEs no vento solar (do inglês solar wind, SW), o choque e o envoltório (do inglês sheath, Sh) são estabelecidos. Nesta fase, a transferência da energia e a termalização do choque podem ter origem através de vários processos, entre eles instabilidades e aceleração de partculas. Aqui nós apresentamos dois estudos relacionados às CMEs. No primeiro estudo, analisamos a existência da instabilidade KelvinHelmholtz (KHI) nas interfaces CMESh e ShSW. Para isto, supomos duas CMEs que se propagam independentemente no SW lento e rápido. Modelamos as velocidades, densidades e a intensidade do campo magnético dos envoltórios e SW nos flancos das CMEs, a fim de resolver a condição de Chandrasekhar para a existência da KHI magnética. Nossos resultados revelam que a formação da KHI pode ser mais provável na CME que se propaga no SW lento do que na CME que se propaga no SW rápido. Isto é devido a um maior cisalhamento entre a CME e o SW lento. Além disso, encontramos que a interface ShSW é ser mais suscetvel à instabilidade. No segundo estudo, examinamos as distribuições das regiões de aceleração de partculas e turbulência em choques ondulados com caractersticas semelhantes a ondas. Assumimos choques ondulados como resultado de perturbações do SW bimodal, deflexão da CME, expansão irregular da CME, e flutuações onipresentes na coroa solar. Construmos choques sem ondulações usando perfis Gaussianos. Com adição de funções semelhantes a ondas, obtemos os choques ondulados. Para ambos tipos de choques, calculamos os ângulos entre o vector normal ao choque e o campo magnético coronal radial, assim classificamos as regiões como quase-paralelas e quase-perpendiculares que são ligadas às regiões de aceleração de partculas e turbulência, respectivamente. Nossos cálculos mostram a predisposição do choque para o fenômeno de acceleração de partculas, e indicam que a expansão irregular da CME é o fator de maior relevância neste processo. Consideramos que assumir ondulações nos choques pode ser essencial nos estudos de problemas atuais como injeção de partculas, instabilidades, jatos e termalização dos choques.

The interaction of a shock wave with a boundary layer is a classic viscous/inviscid interaction problem that occurs over a wide range of high speed aerodynamic flows. For example, on transonic wings, in supersonic air intakes, in propelling nozzles at offdesign conditions and on deflected controls at supersonic/transonic speeds, to name a few. The transonic interaction takes place at Mach numbers typically between 1.1 and 1.5. On an aerofoil, its existence can cause problems that range from a mild increase in section drag to flow separation and buffeting. In the absence of separation the drag increase is predominantly due to wave drag, caused by a rise in entropy through the interaction. The control of the turbulent interaction as applied to a transonic aerofoil is addressed in this thesis. However, the work can equally be applied to the control of interaction for numerous other occurrences where a shock meets a turbulent boundary layer. It is assumed that, for both swept normal shock and unswept normal shock interactions, as long as the Mach number normal to the shock is the same, then the interaction, and therefore its control, should be the same. Numerous schemes have been suggested to control such interaction. However, they have generally been marred by the drag reduction obtained being negated by the additional drag due to the power requirements, for example the pumping power in the case of mass transfer and the drag of the devices in the case of vortex generators. A system of piezoelectrically controlled flaps is presented for the control of the interaction. The flaps would aeroelastically deflect due to the pressure difference created by the pressure rise across the shock and by piezoelectrically induced strains. The amount of deflection, and hence the mass flow through the plenum chamber, would control the interaction. It is proposed that the flaps will delay separation of the boundary layer whilst reducing wave drag and overcome the disadvantages of previous control methods. Active control can be utilised to optimise the effects of the boundary layer shock wave interaction as it would allow the ability to control the position of the control region around the original shock position, mass transfer rate and distribution. A number of design options were considered for the integration of the piezoelectric ceramic into the flap structure. These included the use of unimorphs, bimorphs and polymorphs, with the latter capable of being directly employed as the flap. Unimorphs, with an aluminium substrate, produce less deflection than bimorphs and multimorphs. However, they can withstand and overcome the pressure loads associated with SBLI control. For the current experiments, it was found that near optimal control of the swept and unswept shock wave boundary layer interactions was attained with flap deflections between 1mm and 3mm. However, to obtain the deflection required for optimal performance in a full scale situation, a more powerful piezoelectric actuator material is required than currently available. A theoretical model is developed to predict the effect of unimorph flap deflection on the displacement thickness growth angles, the leading shock angle and the triple point height. It is shown that optimal deflection for SBLI control is a trade-off between reducing the total pressure losses, which is implied with increasing the triple point height, and minimising the frictional losses.

The growing requirements to achieve hypersonic flights, as in the case of reentry vehicles, pose a serious challenge to the designers. This demands an understanding of the features of hypersonic flow and its effect on hypersonic vehicles. Hypersonic shock tunnels are one of the most widely used facilities for the purpose of obtaining valuable design data by conducting experiments on scaled down models. They are operated by conventional shock tubes by rupturing metal diaphragms placed between the driver and driven sections of the shock tube. Shock tunnels are being extensively used in spite of some of the drawbacks they possess. Due to the varying nature of metal diaphragm rupture, reproducibility of the experiment results is difficult to obtain. Damage to model and inner surface of the shock tube can happen when the diaphragm petal breaks away from the diaphragm. Lastly the time consuming diaphragm replacement process is not desired in applications which require quick loading of shock waves on the specimen. All these disadvantages call for the replacement of the diaphragm mode of operation with a diaphragmless mode of operation for the generation of shock waves. The main objective of the present study is to design and demonstrate the working of a diaphragmless hypersonic shock tunnel. The motivation for the present study comes from the fact that the diaphragmless operation of a shock tunnel has not been reported so far in the open literature. All the research works carried out deal with diaphragmless drivers operating only a shock tube. In the present work, the conventional metal diaphragm is substituted by fast acting pneumatic valves which serve the purpose of quickly opening the driven section of the shock tube to allow the driver gas to rush in, resulting in the formation of a shock wave. To design a diaphragmless driver, a detailed study of the shock formation process is accomplished which helps in understanding the effect of valve opening time on the shock formation distance. Also the theoretical basis for the design of a pneumatic cylinder is understood. Following the theoretical studies, three types of diaphragmless drivers are designed and tested. The first setup incorporates a rubber membrane, which acts as a valve. The rubber membrane when bulged closes the mouth of the driven section and on retraction the driven section is opened to the driver gas. The second and the third setups utilise two different types of double acting pneumatic cylinders. Experimental results of the three diaphragmless drivers operating a shock tube are analysed and compared with the ideal shock tube theory. Better repeatability in terms of shock Mach number is shown with all three diaphragmless shock tubes when compared with a conventionally operated shock tube. Finally, the best among the three systems is identified to operate the hypersonic shock tunnel 2 (HST2) facility of the Shock Waves laboratory, IISc. Demonstration of the working of the diaphragmless shock tunnel is shown by performing heat transfer measurements on a 3 mm backward facing step flat plate model. The experimental results are compared with those obtained in a conventional shock tunnel. CFD studies on diaphragmless shock tube model are done to have an idea on the flow in the shock tube there by identifying the shock formation distance. ANSYS-CFX package is used for this purpose. Further, results from the numerical simulation of hypersonic flow over the backward facing step model are compared with the experimental results thus validating the code.

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Die vorliegende Arbeit beschreibt die Ergebnisse der Synthese und Charakterisierung der Hochdruckphase von Aluminiumnitrid mit Kochsalzstruktur (rs-AlN). Die Versuche wurden mittels Schockwellensynthese unter Verwendung der „flyer-plate-Methode“ mit anschließender Probenrückgewinnung durchgeführt. Für verschiedene Aluminiumnitridpulver mit einer Ausgangsporosität k = rho_solid/rho_porous von 1,5 bis 2,5 wurde bei einem Druck von 15 bis 43 GPa die Phasenumwandlung von der Wurtzitstruktur (w-AlN) in die Kochsalzstruktur (rs-AlN) bewirkt. Es ist damit erstmals gelungen, rs-AlN mit dynamischen HP-HT-Methoden herzustellen und damit Probenmengen im Milligramm- bis Grammbereich zu erhalten. Dadurch ist es möglich Untersuchungen durchzuführen, die zur weiteren Erforschung und Charakterisierung des Materials beitragen sollen. Im Fokus liegen dabei insbesondere die Untersuchung der mechanischen, thermischen und chemischen Stabilität, um die Eignung des Materials zur Herstellung ultraharter Komposite zu evaluieren. Die geschockten Pulver bestehen aus einem Phasengemisch aus dem Ausgangsmaterial (w-AlN), der Hochdruckphase (rs-AlN), Aluminiumoxid und -oxynitriden, sowie amorphen Aluminiumhydroxiden. Die höchste Ausbeute an rs-AlN (~41 Ma% bei 2 mm Probenhöhe) kann bei Drücken von 24 GPa und einer Ausgangsporosität k von 2,1 erhalten werden. Anhand dem Auftreten verschiedener Al-O-N Phasen kann die Schocktemperatur für die einzelnen Versuche abgeschätzt werden (<1700 °C bis <2000 °C). Die Phasenumwandlung wird durch die Temperaturerhöhung aufgrund der Schockkompaktion der Pulver aktiviert. Als entgegenwirkender Prozess wurde die thermisch aktivierte Rückwandlung in die Niederdruckphase w-AlN aufgrund einer zu hohen Post-Schocktemperatur und einem zu langsamen Abkühlen der Probe postuliert. Daraus ergibt sich eine optimale Temperatur für den Versuchsaufbau von 1700 bis 1900 °C, bei der die höchsten rs-AlN Anteile beobachtet wurden. Eine Verringerung der Probenhöhe erhöht den Einfluss von Mehrfachreflektionen in der Probe und trägt damit zur Verbesserung der Umsetzung bei. Für drei Nanopulver (Kristallitgröße <25 nm) wurde die teilweise Umwandlung in die Kochsalzstruktur beobachtet, wohingegen für ein gröberes Nanopulver und ein Submikropulver (Kristallitgröße >45 nm) kein rs-AlN in den geschockten Proben nachgewiesen werden konnte. Es wird ein Stabilisierungsmechanismus der Kochsalzstruktur durch Kristallitgrößeneffekte vorhergesagt. Die Verringerung der Kristallitgröße führt zur Herabsetzung des Umwandlungsdrucks w-AlN -> rs-AlN. Es lässt sich daher schlussfolgern, dass für kleinere Partikel die Hochdruckmodifikation aufgrund der geringeren Entfernung vom chemischen Gleichgewicht bei Normalbedingungen stabilisiert werden kann, wohingegen für größere Kristallite die Rückwandlung in die Ausgangsphase geschieht. Weitere Stabilisierungsmechanismen wurden diskutiert. Mithilfe einer Rietveld-Verfeinerung der Röntgendiffraktogramme wurde die Gitterkonstante des rs-AlN mit a = 4,044 ± 0,001 Å und die Kristallitgröße mit 15,3 ± 0,2nm bestimmt. Die mittels hoch-aufgelöster Transmissionselektronenmikroskopie (TEM) bestimmte Kristallitgröße (10 bis 20 nm) ist in guter Übereinstimmung mit den Ergebnissen der Rietveld-Verfeinerung. Mit 27Al Kernspinresonanzspektroskopie (NMR) wurde die oktaedrische Al–N-Umgebung (AlN6) mit einer korrigierten chemischen Verschiebung von 2 ppm nachgewiesen. Anhand der IR-Spektren wird eine Al–N-Schwingungsbande des rs-AlN bei ca. 490 cm−1 vermutet. Dynamisch-thermische Untersuchungen zeigen, dass nanokristallines rs-AlN bei 600 °C beginnt zu Aluminiumoxid zu oxidieren und damit keine größere Beständigkeit im Vergleich zum w-AlN zeigt. Die thermisch aktivierte Rückwandlung des rs-AlN in die Niederdruckphase wurde ab 1200 °C (in Argon) bzw. 1100 °C (im Vakuum) bei einer Heizrate von 10 K/min beobachtet. Eine gute chemische Beständigkeit des Aluminiumnitrid mit Kochsalzstruktur gegenüber Wasser, Natronlauge und Säuren (HCl, H2SO4, H3PO4, HNO3 und Königswasser) wurde in Langzeit-Löslichkeitsversuchen nachgewiesen. / In the present work the results of the synthesis and characterisation of the high-pressure phase of aluminium nitride with rocksalt structure (rs-AlN) are presented. The experiments were carried out with the flyer-plate-method with subsequently sample recovery. For different aluminium nitride powders with starting porosities k = rho_solid/rho_porous of 1.5 to 2.5 the phase transition from wurtzite structure (w-AlN) to the rocksalt structure (rs-AlN) was induced at a pressure of 15 to 43 GPa. This is to our knowledge the first succesful synthesis of rs-AlN with dynamic HP-HT methods. With this advance, samples in the milligram or gram range can be produced. Therefore further investigations to characterise the material are possible, especially the study of the mechanical, thermal and chemical stability to validate the potential for the production of ultrahard composites. The shocked samples consist of a phase mixture from the starting material (w-AlN), the high-pressure phase (rs-AlN), aluminium oxide and oxynitrides, as well as amorphous aluminium hydroxides. The highest yield of rs-AlN (~41 wt% at 2 mm sample height) can be obtained at a pressure of 24 GPa and a starting porosity k of 2.1. The shock temperature can be estimated by the formation of different Al-O-N phases (<1700 °C to <2000 °C). The phase transition is activated by the raise of temperature due to shock compression. A thermal activated reconversion to the low-pressure phase w-AlN caused by a high post-shock temperature and a slow cooling of the sample is postulated as a contrary process. This results in an optimum temperature of 1700 to 1900 °C for this set-up. A decrease of the sample height increases the influence of multiple reflections and therefore causes a better transformation. A partial conversion to rs-AlN was observed for three nanopowders (crystallite size <25 nm), whereas for a more coarse nanopowder and an submicronpowder (crystallite size >45 nm) no rs-AlN could be found in the shocked samples. A stabilisation mechanism of the rocksalt phase by crystallite size effects is predicted. The reduction of the crystallite size causes a decrease of the transition pressure for w-AlN -> rs-AlN. It can be concluded, that for smaller particles the high-pressure phase can be stabilised at ambient conditions on the basis of the smaller distance from equilibrium, whereas for larger particles the reconversion to the low-pressure phase occurs. By a Rietveld refinement of the X-ray diffractograms, the lattice constant of rs-AlN and the crystallite size was determined to be a = 4.044 ± 0.001 Å respectively 15.3 ± 0.2 nm. The crystallite size of rs-AlN (10 to 20 nm) determined with high-resolution transmission electron microscopy (TEM) is in good agreement with the results of the Rietveld refinement. The octahedral Al–Npolyhedral (AlN6) was demonstrated by 27Al nuclear magnetic resonance spectroscopy (NMR) with a corrected chemical shift of 2 ppm. Based on infrared spectroscopy (FTIR) an AlN vibration band at about 490 cm−1 is assumed. Dynamic thermal analysis show, that the rs-AlN starts to oxidise to alumina at 600 °C and thus have no greater resistance in comparison with w-AlN. The thermal activated reconversion of rs-AlN to the low-pressure phase starts at 1200 °C (in argon) respectively 1100 °C (under vacuum) at a heating rate of 10 K/min. The aluminium nitride with rocksalt structure shows a good chemical resistance against water, caustic soda and acids (HCl, H2SO4, H3PO4, HNO3 and aqua regia).

The interaction of a shock wave with a boundary layer is a classic viscous/inviscid interaction problem that occurs over a wide range of high speed aerodynamic flows. For example, on transonic wings, in supersonic air intakes, in propelling nozzles at offdesign conditions and on deflected controls at supersonic/transonic speeds, to name a few. The transonic interaction takes place at Mach numbers typically between 1.1 and 1.5. On an aerofoil, its existence can cause problems that range from a mild increase in section drag to flow separation and buffeting. In the absence of separation the drag increase is predominantly due to wave drag, caused by a rise in entropy through the interaction. The control of the turbulent interaction as applied to a transonic aerofoil is addressed in this thesis. However, the work can equally be applied to the control of interaction for numerous other occurrences where a shock meets a turbulent boundary layer. It is assumed that, for both swept normal shock and unswept normal shock interactions, as long as the Mach number normal to the shock is the same, then the interaction, and therefore its control, should be the same. Numerous schemes have been suggested to control such interaction. However, they have generally been marred by the drag reduction obtained being negated by the additional drag due to the power requirements, for example the pumping power in the case of mass transfer and the drag of the devices in the case of vortex generators. A system of piezoelectrically controlled flaps is presented for the control of the interaction. The flaps would aeroelastically deflect due to the pressure difference created by the pressure rise across the shock and by piezoelectrically induced strains. The amount of deflection, and hence the mass flow through the plenum chamber, would control the interaction. It is proposed that the flaps will delay separation of the boundary layer whilst reducing wave drag and overcome the disadvantages of previous control methods. Active control can be utilised to optimise the effects of the boundary layer shock wave interaction as it would allow the ability to control the position of the control region around the original shock position, mass transfer rate and distribution. A number of design options were considered for the integration of the piezoelectric ceramic into the flap structure. These included the use of unimorphs, bimorphs and polymorphs, with the latter capable of being directly employed as the flap. Unimorphs, with an aluminium substrate, produce less deflection than bimorphs and multimorphs. However, they can withstand and overcome the pressure loads associated with SBLI control. For the current experiments, it was found that near optimal control of the swept and unswept shock wave boundary layer interactions was attained with flap deflections between 1mm and 3mm. However, to obtain the deflection required for optimal performance in a full scale situation, a more powerful piezoelectric actuator material is required than currently available. A theoretical model is developed to predict the effect of unimorph flap deflection on the displacement thickness growth angles, the leading shock angle and the triple point height. It is shown that optimal deflection for SBLI control is a trade-off between reducing the total pressure losses, which is implied with increasing the triple point height, and minimising the frictional losses.