Modern Dry Low Emissions (DLE) combustors are characterized by highly swirling and expanding flows that makes the convective heat load on the combustor liner gas side difficult to predict and estimate. A coupled experimental-numerical study of swirling flow and its effects on combustor liner heat transfer inside a DLE annular combustor model is presented. A simulated scaled up annular combustor shell was designed with a generic fuel nozzle provided by Solar Turbines to create the swirl in the flow. The experiment was simulated with a cold flow and heated walls. An infrared camera was used to obtain the temperature distribution along the liner wall. Experimentally measured pressure distributions were compared with the heat transfer results. The experiment was conducted at various Reynolds Numbers to investigate the effect on the heat transfer peak locations and pressure distributions. A CFD study was performed using Fluent and turbulence models and used to corroborate and verify the experimental results. Results show that the heat transfer enhancement in the annulus has slightly different characteristics for the concave and convex walls. Results also show a much slower drop in heat transfer coefficient enhancement with increasing Reynolds number compared to can combustors from a previous study. An introductory study of the effect of a soft wall on the heat transfer on the combustor liner is also presented. / Master of Science

Despite many advances in aviation noise control over the past 50 years, the industry is continually striving to reduce noise emissions. Turbofan engine acoustic liners are efficient attenuators of engine noise. Plasma actuators have been used as flow control devices in other settings and will now be studied as an enhancement for acoustic liners. A plasma actuator can excite oscillatory flow or a single direction (bias flow). Both flow types are studied as possible means to excite turbofan liners in order to improve the acoustic performance. Experiments revealed the oscillatory flow as the dominant factor in controlling resonator performance. The phase control of the actuator signal is an important parameter when dealing with the oscillatory flow. The actuator is first applied to a single resonator and then a set of six resonators. The experiments show that with the correct phase, the actuators improved the performance of a single resonator by 3 dB to 5 dB. The results for the array of actuators/resonators mirror the results of a single device. Beyond the improvements in performance, a number of other factors affect the usefulness of the plasma actuator technology in a turbofan environment. The ability of the actuator to produce plasma is susceptible to small imperfections in the device, and this property will likely be amplified in a perforated sheet with embedded actuators. Additional weight and energy consumed by the actuators is another factor to consider. Finally, plasma actuator operation produces ozone, so environmental effects deserve consideration as well. / Master of Science

Avaliou-se, experimentalmente, o efeito da contaminação, por uma solução de cloreto de cobre, na resistência ao cisalhamento de solos a serem utilizados na construção de liners. Foi escolhido o cloreto de cobre como contaminante pelo fato de os íons cobre serem os mais comuns nos aterros sanitários industriais. Apresentam-se resultados de ensaios de percolação em colunas e ensaios triaxiais convencionais do tipo CU para solos provenientes das formações Serra Geral (argilosos), Botucatu (arenosos) e uma mistura dos mesmos na proporção de 20% de solo Serra Geral e 80% de solo Botucatu. A mistura apresentou condutividade hidráulica e resistência mais adequadas para utilização em liners do que cada um dos solos isolados. Da análise dos resultados dos ensaios triaxiais do tipo CU, constatou-se a maior influência da contaminação no comportamento do solo Serra Geral, como conseqüência da dupla camada elétrica. Para os três solos, observou-se que o efeito da contaminação foi mais pronunciado para menores tensões confinantes / The contamination effects of copper chloride, on the shear strength of soils to be used as liners, were experimentally testes in laboratory. The copper chloride was chosen as the contaminant agent because it is the most common in found in industrial sanitary landfills. The results of percolation and conventional triaxial tests for soils from Serra Geral formation (clayed soils), Botucatu formation (sandy soils) and a mix in a convenient proportion with both soils are presented. The hydraulic condutivity and strength of the mixed soil indicated that it is more suitable to be used as liners than the original soils. From the comparison of triaxial test results, the effects of contamination were more significant in the soils from the Serra Geral formation as a consequence of the electrical double layer. For the three soils, the effects of contamination were more noticeable for smaller confining pressures

Ce travail de thèse s’inscrit dans l’effort de réduction des nuisances sonores dues à la soufflante d’unréacteur double-flux à l’aide de matériaux absorbants acoustiques, appelés communément «liners». Afind’optimiser ces traitements acoustiques, il convient d’étudier en détail la physique de la propagationacoustique en présence de liner. De plus, il s’agit d’améliorer la compréhension des instabilités hydrodynamiquespouvant se développer sur un liner sous des conditions particulières et possiblement génératricesde bruit. Ce travail de thèse a consisté à développer un code de calcul en formulation Galerkin discontinuepour l’analyse modale et la stabilité dans un conduit traité acoustiquement, code qui a été appliqué à desconfigurations réalistes, en considérant une section transverse ou longitudinale d’un conduit. Les étudesmodales réalisées dans la section transverse ont apporté des informations sur la propagation acoustiquedans une nacelle de turbofan avec des discontinuités du traitement acoustique («splices»), ainsi que dansle banc B2A de l’ONERA. Les calculs dans la section longitudinale ont nécessité l’implantation de conditionsaux limites PML pour tronquer le domaine de calcul, ainsi que d’une condition aux limites sur leliner, modélisée en domaine temporel à partir d’une extension de travaux existants dans la littérature.Avec ces outils, le code a permis de mettre en évidence une dynamique de type amplificateur de bruit dueau développement d’une instabilité hydrodynamique sur le liner en présence d’écoulement cisaillé ainsiqu’un rayonnement acoustique en amont et en aval du conduit dû à cette instabilité. / The current work deals with the reduction of aircraft engine fan noise using acoustic lining. In orderto optimise these liners, it is necessary to deeply understand the physics of acoustic wave propagation in lined ducts and to have a better knowledge of the hydrodynamic instabilities existing under particular conditions and likely to radiate noise. This work is about the development of a discontinuous Galerkin solver for modal and stability analysis in lined flow duct and the application of this solver to realistic configurations by considering the transverse or longitudinal section of a duct. The modal studies in the transverse section brought informations on acoustic propagation in a turbofan nacelle with lining discontinuities (“splices”) and in the B2A bench of ONERA. The computation in the longitudinal section of a duct required the implementation of PML boundary conditions in order to truncate the computational domain and of a boundary condition at the lined wall, modeled in temporal domain by the enhancement of a method published in the literature. With these features, the application of the solver highlighted a noise amplifier dynamics caused by the development of a hydrodynamic instability on the liner with sheared flow and a noise radiation mechanism upstream and downstream the lined section.

Avaliou-se, experimentalmente, o efeito da contaminação, por uma solução de cloreto de cobre, na resistência ao cisalhamento de solos a serem utilizados na construção de liners. Foi escolhido o cloreto de cobre como contaminante pelo fato de os íons cobre serem os mais comuns nos aterros sanitários industriais. Apresentam-se resultados de ensaios de percolação em colunas e ensaios triaxiais convencionais do tipo CU para solos provenientes das formações Serra Geral (argilosos), Botucatu (arenosos) e uma mistura dos mesmos na proporção de 20% de solo Serra Geral e 80% de solo Botucatu. A mistura apresentou condutividade hidráulica e resistência mais adequadas para utilização em liners do que cada um dos solos isolados. Da análise dos resultados dos ensaios triaxiais do tipo CU, constatou-se a maior influência da contaminação no comportamento do solo Serra Geral, como conseqüência da dupla camada elétrica. Para os três solos, observou-se que o efeito da contaminação foi mais pronunciado para menores tensões confinantes / The contamination effects of copper chloride, on the shear strength of soils to be used as liners, were experimentally testes in laboratory. The copper chloride was chosen as the contaminant agent because it is the most common in found in industrial sanitary landfills. The results of percolation and conventional triaxial tests for soils from Serra Geral formation (clayed soils), Botucatu formation (sandy soils) and a mix in a convenient proportion with both soils are presented. The hydraulic condutivity and strength of the mixed soil indicated that it is more suitable to be used as liners than the original soils. From the comparison of triaxial test results, the effects of contamination were more significant in the soils from the Serra Geral formation as a consequence of the electrical double layer. For the three soils, the effects of contamination were more noticeable for smaller confining pressures

L’étude présentée dans cette thèse se situe dans le domaine de l’acoustique modale des conduits avec des parois absorbantes et un écoulement moyen. Nous considérons une source de bruit en amont avec une fréquence fixe. Avec cela, nous étudions les modes propres acoustiques du conduit en terme de nombre d’onde qui sont présents.Avec cette étude, nous contribuons à la meilleure compréhension de la propagation du sondans ce type de configuration. Parmi les applications, il y a la réduction du bruit des moteurs des aéronefs.Une analyse numérique par la méthode pseudospectrale de collocation, sur la base de polynômes de Chebyshev, a été mise en ouvre pour obtenir le spectre des modes, dans un domaine transversal.Pour cela, deux programmes ont été utilisés : le programme FiEStA, qui a été développé dans le cadre de cette thèse, et qui résout les équations d’Euler linéarisées, en considérant un problème à une ou deux une ou deux dimensions. D’autre part, le programme MAMOUT, a été utilisé pour résoudre les équations de Navier-Stokes linéarisées, pour étudier plus spécifiquement les effets de la viscosité.Avec ces outils, on a constaté les effets de trois paramètres : lorsque le rapport d’aspect augmente, la densité des modes, en particulier des modes propagatifs, se développe également.Quand le nombre de Mach de l’écoulement moyen augmente, on observe les effets suivants sur les valeurs propres : un déplacement vers la partie réelle négative, une amplification de leur valeur absolue et un déplacement vers les modes d’indice inférieur. Le profil d’écoulement moyen induit aussi un déplacement dans les valeur propres, pas facilement prévisible. Il modifie également la forme des fonctions propres ; ce qui est notamment visible pour le mode d’onde plane. Les changements d’impédance induisent un échange cyclique de valeurs propres entre les valeurs de parois rigides des modes consécutifs. Avec certaines valeurs d’impédance, les modes acoustiques de paroi apparaissent. Ils sont caractérisés par la forme exponentielle de leurs fonctions propres.En plus des modes acoustiques, il existe des modes hydrodynamiques de surface qui se sont révélés avec quelques valeurs d’impédance et forme et nombre de Mach de l’écoulement moyen. Pour un ensemble de données de référence, ces modes ont été étudiés. L’impédance a été considérée avec un modèle basé sur des données de la littérature, tout comme le profil d’écoulement moyen.Un mode hydrodynamique a été trouvé. Avec certaines valeurs de la fréquence, l’ensemble des paramètres donne lieu à une instabilité. En utilisant le critère Briggs Bres pour la stabilité,l’instabilité a été jugée absolue.À partir du comportement des modes avec différentes valeurs de l’impédance, et conformément aux résultats publiés, nous avons défini la condition que le spectre doit remplir pour réduire autant que possible le bruit. C’est cela qu’on appelle l’impédance optimale. Nous avons calculé cette valeur pour différents fréquences et écoulements moyens. / The study presented in this thesis is within the domain of modal acoustics of lined ducts withgrazing flow. We consider an upstream source of noise with a fixed frequency, within a lined duct.From this, we study the eigenmodes in terms of wavenumber that are present in this system.With this study, we contribute to the better understanding of sound propagation in thedescribed configuration. Within its main applications, we can find the noise reduction fromaeroengines.A numerical analysis with the pseudospectral collocation method, based on Chebyshevpolynomials was used to obtain the spectrum of modes within the duct, in a domain transversalto the mean flow. For this, two programs were used: On one hand, within the frame of this thesis,the program FiEStA was developed. It solves the linearized Euler Equations, considering eitherone or two dimensions of the transversal plane. On the other hand, the already existing programMAMOUT was used for verification and to solve also the linearized Navier-Stokes Equations toobserve the effects of viscosity.With these tools, the first result was to notice the effects of three parameters: When theaspect ratio grows, the density of modes in the spectrum grows also. In particular, we havemore propagative modes. As the mean flow Mach number grows, we observe these effects on theeigenvalues: a displacement to the negative real part, a slight amplification of their absolute valueand a displacement towards the modes of lower index. The difference in mean flow profile inducesanother displacement in modes, not easily predictable. It changes also the shape of eigenfunctions,which is clearly seen for the planewave mode. The impedance changes induce a cyclic exchange ofeigenvalues from their hard wall value to the hard wall value of a consecutive mode. The changeof eigenfunction is gradually change in wavelength, to obtain the shape of the destination mode.With some impedance values, a pair of modes, called the acoustic surface modes arise. They arecharacterized by the exponential shape of their eigenfunctions.Besides these acoustic surface modes, there are also a pair of hydrodynamic surface modeswhich come to light with some values of impedance and shape and Mach number of the meanflow. With a benchmark data, these modes were studied. The impedance was considered from themodel of a measured liner while the mean flow profile was taken from experimental values. Withthis, the hydrodynamic mode was found. With specific values of frequency, the set of parametersgives rise to an instability. Using the Briggs-Bers criterion for stability, the instability was foundto be absolute for a given frequency.From the comportment of modes with different values of impedance, and in accordance withpublished results, we defined the condition that the spectrum has to fulfill to reduce as much aspossible the upstream noise. This is what we called the optimal impedance. We obtained it forseveral flow profiles and frequencies, in both 1D and 2D domains.

Este trabalho trata do desenvolvimento, montagem e teste de equipamentos para ensaios de materiais de baixa condutividade hidráulica, o qual inclui sistemas de controle hidráulico de volume constante, permeâmetros do tipo parede flexível e interfaces água-percolante. A vantagem desse arranjo está no maior controle dos ensaios e, notadamente, na redução do tempo de ensaio com emprego do sistema hidráulico de volume constante (sistema fechado), quando comparado aos ensaios que empregam o sistema aberto de controle hidráulico. Para testar o equipamento, foram ensaiados geocompostos bentoníticos (geosynthetic clay liners - GCLs) de fabricação nacional, em corpos de prova moldados com diâmetro de 100 mm e também, em uma mistura de solo com bentonita. Os resultados da condutividade hidráulica obtidos para os geocompostos bentoníticos se situaram na ordem de \'10 POT.-9\' e \'10 POT.-10\' cm/s, compatíveis com os publicados na literatura sobre o material, e os ensaios na mistura solo-bentonita produziu resultados na ordem de \'10 POT.-8\' cm/s, e foram conseguidos com cerca de 3 horas de ensaio. Aborda-se ainda a aplicabilidade da lei de Darcy aos materiais ensaiados. / This work describes the development, construction, calibration and test of equipment for testing low hydraulic conductivity materials, which includes constant volume hydraulic control system, flexible wall permeameters and permeating water interfaces. The advantage of this kind of apparatus is the greater test control, notably, the reduction of test duration due to the use of a constant volume hydraulic system (closed system), when compared to the opened system hydraulic control test. In order to test the equipment, geosynthetic clay liners (GCLs) manufactured in Brazil was used as test specimens of 100 mm diameter and also, a mixture of soil and bentonite. The results of hydraulic conductivity obtained for the GCL were in the range of \'10 POT.-9\' to \'10 POT.-10\' cm/s, comparable to what has been published by the specialized literature on this material, and the tests with the soil-bentonite mixture resulted in a conductivity about \'10 POT.-8\' cm/s, after 3 hours running the test. The applicability of Darcy´s law to the tested materials is also referred to.

La réduction des nuisances sonores est un enjeu permanent pour les acteurs de l’aéronautique. L’optimisation de la réduction de bruit apportée par les traitements acoustiques tapissant la nacelle des réacteurs turbofan passe par une caractérisation précise des matériaux employés dans l’environnement aéroacoustique d’utilisation, qui met en jeu un écoulement rasant de vitesse importante combiné à de forts niveaux sonores. L’objectif de cette thèse est de développer une méthode inverse pour la détermination de l’impédance acoustique de liners soumis à un écoulement rasant, basée sur des mesures non intrusives du champ de vitesse acoustique au-dessus du matériau par Vélocimétrie Laser Doppler (LDV). L’impédance de liner est obtenue par minimisation de l’écart entre le champ de vitesse acoustique mesuré et le champ simulé numériquement en résolvant les équations d’Euler linéarisées bidimensionnelles harmoniques, discrétisées par un schéma Galerkin discontinu. Le gradient de la fonction objectif minimisée est calculé via la résolution, à chaque itération, des équations directes et adjointes. Une première étape de validation du solveur est effectuée sur des cas-tests académiques, puis sur des cas expérimentaux impliquant des mesures de pression acoustique en paroi rigide opposée au liner. Dans un second temps, la méthode est appliquée à des mesures de vitesse acoustique obtenues par LDV dans le banc B2A de l’ONERA en l’absence d’écoulement. La dernière étape consiste à prendre en compte l’effet d’un écoulement rasant de profil cisaillé. Les impédances identifiées à partir de mesures LDV en présence d’écoulement ont notamment permis de gagner en compréhension sur les phénomènes d’absorption intervenant dans le banc B2A. / While aircraft noise constraints become increasingly stringent, efficient duct treatment of turbofan engines requires an accurate knowledge of liner impedance with grazing flow at high acoustic levels. This thesis aims at developing an impedance eduction method in the presence of grazing flow. The inverse process is based on acoustic velocity fields acquired by Laser Doppler Velocimetry (LDV) above the liner. The liner acoustic impedance is obtained by minimization of the distance between the measured acoustic velocity field and the simulated one. Computations rely on the resolution of the 2D linearized Euler equations in the harmonic domain, spatially discretized by a discontinuous Galerkin scheme. The gradient of the objective function is achieved by the resolution, at each iteration on the liner impedance, of the direct and adjoint equations. The solver is first validated on academic test cases, then on experimental results of acoustic pressure measurements at the rigid wall opposite the liner. Secondly the method is applied to acoustic velocity measurements obtained by LDV above the liner without flow, in the ONERA B2A test bench. The last step consists in taking into account the effects of a sheared grazing flow. The impedances educed from LDV measurements in the presence of flow namely allowed to gain insight into the absorption phenomena occuring in the B2A test bench.

Este trabalho trata do desenvolvimento, montagem e teste de equipamentos para ensaios de materiais de baixa condutividade hidráulica, o qual inclui sistemas de controle hidráulico de volume constante, permeâmetros do tipo parede flexível e interfaces água-percolante. A vantagem desse arranjo está no maior controle dos ensaios e, notadamente, na redução do tempo de ensaio com emprego do sistema hidráulico de volume constante (sistema fechado), quando comparado aos ensaios que empregam o sistema aberto de controle hidráulico. Para testar o equipamento, foram ensaiados geocompostos bentoníticos (geosynthetic clay liners - GCLs) de fabricação nacional, em corpos de prova moldados com diâmetro de 100 mm e também, em uma mistura de solo com bentonita. Os resultados da condutividade hidráulica obtidos para os geocompostos bentoníticos se situaram na ordem de \'10 POT.-9\' e \'10 POT.-10\' cm/s, compatíveis com os publicados na literatura sobre o material, e os ensaios na mistura solo-bentonita produziu resultados na ordem de \'10 POT.-8\' cm/s, e foram conseguidos com cerca de 3 horas de ensaio. Aborda-se ainda a aplicabilidade da lei de Darcy aos materiais ensaiados. / This work describes the development, construction, calibration and test of equipment for testing low hydraulic conductivity materials, which includes constant volume hydraulic control system, flexible wall permeameters and permeating water interfaces. The advantage of this kind of apparatus is the greater test control, notably, the reduction of test duration due to the use of a constant volume hydraulic system (closed system), when compared to the opened system hydraulic control test. In order to test the equipment, geosynthetic clay liners (GCLs) manufactured in Brazil was used as test specimens of 100 mm diameter and also, a mixture of soil and bentonite. The results of hydraulic conductivity obtained for the GCL were in the range of \'10 POT.-9\' to \'10 POT.-10\' cm/s, comparable to what has been published by the specialized literature on this material, and the tests with the soil-bentonite mixture resulted in a conductivity about \'10 POT.-8\' cm/s, after 3 hours running the test. The applicability of Darcy´s law to the tested materials is also referred to.

Neste trabalho analisa-se o comportamento de duas configurações de liners através da percolação com solução de \'K\'CL\'. São utilizadas amostras de solo compactadas, do interior do estado de São Paulo, provenientes da Formação Corumbataí, combinadas a um geocomposto bentonítico (GCL) de fabricação nacional. São utilizados ensaios em coluna de percolação em dois corpos-de-prova, nas configurações: solo compactado acima do GCL e solo compactado abaixo do GCL. Esses ensaios permitiram a determinação da condutividade hidráulica e dos parâmetros de transporte dos materiais estudados. Dessa forma, compara-se o comportamento desses materiais combinados com os resultados obtidos por Musso (2008), que adotou a configuração independente. Após o início da percolação com solução \'K\'CL\' a condutividade hidráulica (\'K\') das duas configurações apresentou comportamento crescente. No entanto, este aumento no \'K\' não afetou o desempenho hidráulico dos materiais, e a condutividade hidráulica mostrou-se com valores da ordem de \'10 POT.-11\' m/s. O fator de retardamento da configuração na qual o GCL encontra-se acima da camada de solo compactado se mostrou maior com relação à outra configuração analisada. No geral, considerou-se que esta configuração apresentou melhor desempenho como liner composto. Na comparação dos resultados obtidos nesta pesquisa com os apresentados por Musso (op. cit.) a condutividade hidráulica não diferiu, e as configurações de liner compostos apresentaram maiores fatores de retardamento do que o liner do solo compactado isoladamente. / This research analyzes the behavior of two sets of liners subjected to the percolation of \'K\'CL\' solution. Samples of compacted soil from Corumbataí Formation, combined with a geosynthetic clay liner (GCL) of brazilian manufacture were used. Column percolation tests were used in two specimens, in the settings: compacted soil above the GCL and compacted soil below the GCL. These tests allowed the determination of hydraulic conductivity and transport parameters of the materials under study. Thus, the behavior of these composite liners was compared with the results obtained by Musso (2008), which tested the independent configuration. After the start of percolation of the \'K\'CL\' solution the hydraulic conductivity (\'K\') of the two settings showed an increase. However, this increase in \'K\' did not affect the hydraulic performance of materials, and the hydraulic conductivity was observed with values of about \'10 POT.-11\' m/s. The retardation factor of the configuration in which the GCL is above the layer of compacted soil was larger in relation to the other configuration analyzed. Overall, it was considered that this configuration showed better performance as composite liner. Comparing the results with those presented by Musso (2008), the hydraulic conductivity didn\'t differ, and the composite liners had higher retardation factors than the liner of compacted soil alone.