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[pt] Esta dissertação apresenta análises dos ensaios de caracterização e de adensamento edométrico realizados em amostras indeformadas extraídas em diferentes profundidades de um depósito de argila mole localizado em Santa Cruz, região oeste da cidade do Rio de Janeiro, nos anos de 2005 e 2008. As amostras foram extraídas de uma região onde o depósito foi submetido ao carregamento de um aterro com cerca de 2,5 m de espessura, construído na década de 1970 para a implantação de uma subestação de energia. Para a interpretação dos resultados dos ensaios edométricos realizados em amostras extraídas cerca de 30 anos após o lançamento do aterro, foi necessária a interpretação detalhada dos dados dos ensaios de laboratório em conjunto com dados de investigações geotécnicas de campo, com a finalidade de estimar o perfil de tensões verticais efetivas in situ no momento da extração das amostras. São apresentados e discutidos dados de compressibilidade e adensamento obtidos dos ensaios edométricos, além de aspectos relativos à qualidade das amostras e à reconstituição das curvas de compressibilidade edométrica das amostras de baixa qualidade. De forma complementar, é realizado um exercício de estimativa do adensamento do depósito sob a carga do aterro na área de extração das amostras, levando em conta o efeito de submersão do aterro e a ocorrência simultânea dos chamados adensamentos primário e secundário. / [en] This dissertation presents analyses of the characterization and one-dimensional consolidation tests carried out on undisturbed samples taken at different depths from a soft clay deposit located in Santa Cruz, western region of Rio de Janeiro city, in 2005 and 2008. The samples were taken from a region subjected to the loading of a 2.5 m thick embankment, built in the 1970s for the implementation of a power substation. To interpret the results of the one-dimensional consolidation tests performed on samples taken about 30 years after the landfill construction, a detailed analysis of the laboratory test data along with field geotechnical investigation data was necessary to allow estimating the in situ vertical effective stress profile when the samples were taken. Compressibility and consolidation data obtained from the one-dimensional consolidation tests are presented and discussed, as well as aspects related to the samples quality and to the reconstruction of the one-dimensional compression curves obtained from the low quality samples. In addition, an estimate of the deposit consolidation under the landfill load at the area where the samples were taken is carried out taking into account the landfill submergence effect as well as the simultaneous occurrence of the so-called primary and secondary consolidations.

No / Rheological characterisation of hydroxyapatite -high density polyethylene (HA-HDPE) composites has been performed in terms of isothermal compressibility and wall slip. Addition of HA to the polymer melt decreases the compressibility of the melt. The unfilled HDPE was found to exhibit wall slip at shear stresses as low as 0.10 MPa. The flow curves of the composites showed three distinct regions: a gradient at low shear rates; a plateau region; and a gradient at higher shear rate. An increase in rheometer pressure seems to suppress the slip in composites. The 40 vol.-% HA-HDPE composite exhibited two critical shear stresses, one corresponding to wall slip, which occurs in the lower shear rate region of the flow curve, and the other corresponding to a plateau, which is identified with the stick-slip behaviour of unfilled HDPE reported in the literature. The plateau shear stress increased with filler volume fraction and this effect is attributed to the decreased compressibility of the melt. A good correlation with a negative correlation coefficient was found to exist between compressibility and shear stress in the plateau region. The slip observed in unfilled HDPE and at low shear rates in the 40 vol.-% HA- HDPE systems has been explained in terms of a low molecular weight polymer layer formed at the melt/wall interface. The large interfacial slip observed in the plateau region is attributed to complete disentanglement of adsorbed chains from free chains at the melt/wall interface at and beyond the plateau region.

The labyrinth seal is a non-contact annular type sealing device used to reduce the internal leakage of the working fluid which is caused by the pressure difference between each stage in a turbomachine. Reducing the leakage mass flow rate of the working fluid through the labyrinth seal is desirable because it improves the efficiency of the turbomachine. The carry-over coefficient, based on the divergence angle of the jet, changed with flow parameters with fixed seal geometry while earlier models expressed the carry-over coefficient solely as a function of seal geometry. For both compressible and incompressible flows, the Reynolds number based on clearance was the only flow parameter which could influence the carry-over coefficient. In the case of incompressible flow based on the simulations for various seal geometries and operating conditions, for a given Reynolds number, the carry-over coefficient strongly depended on radial clearance to tooth width ratio. Moreover, in general, the lower the Reynolds number, the larger is the divergence angle of the jet and this results in a smaller carry-over coefficient at lower Reynolds numbers. However, during transition from laminar to turbulent, the carry-over coefficient reduced initially and once the Reynolds number attained a critical value, the carry-over coefficient increased again. In the case of compressible flow, the carry-over coefficient had been slightly increased if radial clearance to tooth width ratio and radial clearance to tooth pitch ratio were increased. Further, the carry-over coefficient did not considerably change if only radial clearance to tooth width ratio was decreased. The discharge coefficient for compressible and incompressible flows depended only on the Reynolds number based on clearance. The discharge coefficient of the tooth in a single cavity labyrinth seal was equivalent to that in a multiple tooth labyrinth seal indicating that flow downstream had negligible effect on the discharge coefficient. In particular, for compressible fluid under certain flow and seal geometric conditions, the discharge coefficient did not increase with an increase in the Reynolds number. It was correlated to the pressure ratio, Pr. Moreover, it was also related to the fact that the flow of the fluid through the constriction became compressible and the flow eventually became choked. At low pressure ratios (less than 0.7), Saikishan’s incompressible model deviated from CFD simulation results. Hence, the effects of compressibility became significant and both the carry-over coefficient compressibility factor and the discharge coefficient compressibility factor needed to be considered and included into the leakage model. The carry-over coefficient compressibility factor, phi, had two linear relationships with positive and negative slopes regarding the pressure ratios. This result was not associated with the seal geometry because the seal geometry ratios for each instance were located within the nearly same ranges. Further, the phi-Pr relationship was independent of the number of teeth regardless of single and multiple cavity labyrinth seals. The discharge coefficient compressibility factor, psi, was a linear relationship with pressure ratios across the tooth as Saikishan predicted. However, in certain flow and seal geometric conditions, Saikishan’s model needed to be modified for the deviation appearing when the pressure ratios were decreased. Hence, a modified psi-Pr relationship including Saikishan’s model was presented in order to compensate for the deviation between the simulations and his model.

Les matériaux absorbants acoustiques, qui sont d’un intérêt stratégique en aéronautique pour la diminution passive du bruit des réacteurs d’avion, conduisent à une physique complexe où l’écoulement turbulent, des ondes acoustiques, et l’absorbant interagissent. Cette thèse porte sur la simulation de cette interaction dans le problème modèle d’un écoulement de canal turbulent avec des parois impédantes, par le biais de simulations numériques aux grandes échelles implicites, dans un contexte de calcul haute performance.Une étude est d’abord faite des grandes échelles dans un canal turbulent avec des parois rigides, en s’intéressant plus particulièrement à l’effet d’une faible compressibilité (Mach <3) sur les caractéristiques de ces échelles.Un canal turbulent avec une paroi de type impédance est ensuite simulé, avec une condition habituelle de périodicité dans le sens de l’écoulement. On observe que pour des faibles valeurs de la résistance et des fréquences de résonance basses, l’écoulement est instable, ce qui engendre une onde le long de l’absorbant, qui modifie la turbulence et augmente la trainée.Enfin, on se tourne vers une simulation de canal spatial en levant la condition de périodicité dans la direction de l’écoulement, ce qui permet d’introduire une onde acoustique en entrée de domaine. L’atténuation de l’onde dans l’écoulement turbulent est étudiée avec des parois rigides, puis un absorbant acoustique est introduit. Dans cette configuration plus réaliste, il est confirmé que l’écoulement peut devenir instable au bord amont de l’absorbant, ce qui empêche l’atténuation de l’onde acoustique incidente. / Acoustic liners are a key technology in aeronautics for the passive reduction of the noise generated by aircraft engines. They are employed in a complex flow scenario in which the acoustic waves, the turbulent flow, and the acoustic liner are interacting.During this thesis, in a context of high performance computing, a compressible Navier-Stokes solver has been developed to perform implicit large eddy simulations of a model problem of this interaction: a turbulent plane channel flow with one wall modeled as an impedance condition.As a preliminary step the wall-turbulence in rigid channel flows and associated large-scale motions are investigated. A straightforward algorithm to detect these flow features is developed and the effect of compressibility on the flow structures and their contribution to the drag are studied. Then, the interaction between the acoustic liner and turbulent flow is investigated assuming periodicity in the streamwise direction. It is shown that low resistance and low resonance frequency tend to trigger flow instability, which modifies the conventional wall-turbulence and also results in drag increase.Finally, the simulation of a spatial channel flow was addressed. In this case no periodicity is assumed and an acoustic wave can be injected at the inlet of the domain. The effect of turbulence on sound attenuation is studied without liner, before a liner is introduced on a part of the channel bottom wall. In this more realistic case, it is confirmed that low resistance acoustic liners trigger an instability at the leading edge of the liner, resulting in drag increase and excess noise generation.

Dans le cadre de la lutte pour la réduction des émissions de gaz à effet de serre, les biocarburants présentent un potentiel intéressant, en raison notamment de leur bilan CO2 "du puits à la roue" souvent très bon. Ainsi de nombreux programmes sont mis en œuvre, notamment en Europe, pour le développement de nouveaux carburants, et de moteurs automobiles adaptés à ces derniers. La conception de ces derniers nécessite une bonne maîtrise du système d’injection qui doit être aussi parfait que possible. Une meilleure connaissance du comportement et des propriétés sous haute pression de ces biocarburants revêt un caractère important. Le projet français NADIABIO rentre dans ce cadre et a pour principal objectif une meilleure maîtrise de l'injection (de la propagation d'onde dans la ligne HP à l'auto inflammation et la combustion) et de l'impact des biodiesels via une analyse fine à la fois numérique et expérimentale. En effet, dans le domaine des hautes pressions, la détermination des propriétés thermophysiques comme la densité ou les coefficients de compressibilité, présente souvent des difficultés contrairement à la vitesse du son qui peut se mesurer d’une manière simple et directe. Des dispositifs expérimentaux permettant d’effectuer des mesures de vitesses ultrasonores et de densité ont été mis au point pendant ce travail de thèse. Ils ont permis de fournir des données expérimentales de vitesses ultrasonores (pour des pressions et températures allant respectivement de 0,1 à 250 MPa et de 263,15 à 423,15K) et de densité (pour des pressions et températures allant respectivement de 0,1 - 100 MPa et de 283,15 à 393,15K). La campagne de mesure a été effectuée sur 12 biodiesels et sur un ensemble de 7 corps purs (EMHV, EEHV) représentatifs des mélanges étudiés. Cependant, pour des raisons de confidentialité, seuls les résultats relatifs aux corps purs et au Normafluid sont accessibles dans ce mémoire. Parallèlement, dans le but de proposer des méthodes de calcul prédictifs, nous nous somme intéressés à une procédure de type « predictor corrector », à une méthode de contribution de groupes moléculaires ainsi qu’à la théorie des états correspondants. Ces techniques de modélisation ont permis de déduire d’autres propriétés thermophysiques comme les coefficients de compressibilité, sous le même domaine de pression et de température. / Within the politic changes for the reduction of greenhouse gas emissions, biofuels present an interesting potential because of their very well CO2 balance sheet. Numerous projects were engaged in Europe, for the development of new fuels and for the design of automobile engines adapted to these carburant. The conception of new engine requires specific systems of injection which must be perfectly designed. With this aim in mind thermophysical properties such as density and compressibility must be known with accuracy. The French project “NADIABIO” goes into this industrial issue and its main objective consist in a better control of the injection (wave distribution in the High Pressure line, during the automobile inflammation and combustion process) and the impact of biodiesels (FAME and synthetic materials) on the environment through fine numerical and experimental analyses. The direct measurement of the density or the coefficients of compressibility often presents difficulties under high pressure. It is therefore easier to determine it indirectly from the velocity of sound, which can be measured in a simple and direct way with a good accuracy. Therefore, experimental devices allowing to make measurements of ultrasound speeds and density were finalized during this work. Experimental data of ultrasound speeds (from 0,1 to 250 MPa and from 263,15 to 423,15 K) and of density (0,1 to 100 MPa and 283,15 to 403,15K) have been determined with good precision on 19 biodiesels (mixtures and synthetic products (FAME, FAEE)). However, for reasons of confidentiality, only the results relative to the synthetic products and to Normafluid appear in this report. At the same time, with the aim of proposing predictive methods, we are interested in the procedure like “predictor-corrector”, in the method contribution of molecular groups and to the theory of the corresponding states which allowed deducting the other thermophysical properties like the coefficients of compressibility as a function of temperature and pressure.

Les matériaux hybrides de type MOFs sont des solides poreux dans lesquels des centres métalliques sont reliés entre eux par des ligands organiques. Il est possible, non seulement de faire varier la taille et la géométrie de leurs porosités, mais aussi de moduler leurs compositions chimiques en modifiant à la fois la nature de la brique inorganique et des groupements sur le ligand organique. Cette nouvelle famille de matériaux a fait l'objet d'une attention particulière ces dernières années pour des applications potentielles dans différents domaines à fort intérêt socio-économique comme le captage ou la séparation de gaz ou bien encore la catalyse. Au-delà d'une stabilité chimique et thermique, ces matériaux doivent être aussi suffisamment résistants mécaniquement pour s'adapter au mieux aux contraintes de l'application visée (mise en forme de l'échantillon, conditions opératoires….). Il est donc impératif de connaître les propriétés mécaniques de ces nouveaux matériaux, sujet qui n'a fait l'objet à ce jour que de très peu d'études. L'objectif de ce travail est donc de mettre en œuvre des mesures de diffraction des rayons X et neutrons sur grands instruments afin de caractériser dans un premier temps le comportement structural du matériau flexible MIL-53 (MIL pour Matériaux de l'Institut Lavoisier) sous l'application d'une pression mécanique modérée (P~1 GPa) en fonction de la nature du métal (Al,Cr) et de la fonction greffée sur le ligand organique (-H, -Cl, -CH3). Ces données expérimentales sont ensuite discutées à partir de résultats issus de la simulation moléculaire. L'étape suivante consiste à étudier l'effet du confinement de molécules de solvants dans les pores de ce solide sur la transition structurale du réseau hôte. Enfin, deux familles de MOFs rigides, la MIL-125(Ti) et l'UiO-66(Zr) (UiO pour Unversité d'Oslo) sont considérées afin de caractériser non seulement leur domaine de stabilité mécanique en pression (Pmax~ 5 GPa) mais aussi leur compressibilité. Les résultats ainsi obtenus sont comparés aux performances mécaniques des meilleurs MOFs. / Metal Organic Framework (MOF) materials have been the focus of intense research activities over the past 10 years, with the emergence of a wide range of novel architectures, constructed from inorganic clusters linked by organic moieties. In order to maintain their useful functionalities and high performances in the different fields explored so far (gas storage/separation, catalysis, sensors and many others), besides high chemical and thermal stabilities, MOFs must be also stable enough to resist to different mechanical constraints in both processing and applications. Indeed, there is nowadays a growing interest to characterize the mechanical behaviours of this class of materials under moderate and high applied pressure. This work first aimed to probe the pressure dependence of the structural behaviour of the highly flexible MIL-53 system [MIL stands for Materials of Institut Lavoisier] as a function of the nature of (i) the metal center (Al,Cr) and (ii) the functional group grafted on the organic linker (-H,-Cl,-CH3) using a combination of high-pressure x-ray/neutron diffraction and molecular simulations. The same methodology was further applied to probe how the presence of guest molecules affects the structural transition of this class of hybrid porous solids. Finally, the mechanical stability and the compressibility of two families of rigid MOFs, the MIL-125(Ti) and the UiO-66(Zr) [UiO stands for University of Oslo] up to high pressure (P~5 GPa) have been investigated and their properties in terms of bulk modulus were compared with the most resilient MOFs reported so far.

Ideal magnetohydrodynamics (MHD) simulations are known to have problems in satisfying the solenoidal constraint (i.e. the divergence of magnetic field should be equal to zero, $ ablacdotvec{B} = 0$). The simulations become unstable unless specific measures have been taken. In this thesis, a solenoidal constraint satisfying technique that allows discrete satisfaction of the solenoidal constraint up to the machine accuracy is presented and validated with a variety of test cases. Due to its inspiration from Chorin's artificial compressibility method developed for incompressible CFD applications, the technique was named as extit{artificial compressibility analogy (ACA)} approach. It is demonstrated that ACA is a purely hyperbolic, stable and consistent technique, which is moreover easy to implement. Unlike some other techniques, it does not pose any problems of the sort that $ ablacdotvec{B}$ errors accumulate in the vicinity of the stagnant regions of flow. With these crucial properties, ACA is thought to be a remedy to the drawbacks of the most commonly used solenoidal constraint satisfying techniques in the literature namely: Incorrect shock capturing and poor performance of the convective stabilization mechanism in regions of stagnant flow for Powell's source term method; exceedingly complex implementation for constrained transport technique due to the staggered grid representation; computationally expensive nature due to the necessity of a Poisson solver combined with hyperbolic/elliptic numerical methods for classical projection schemes. In the first chapter of the thesis, general background knowledge is given about plasmas, MHD and its history, a certain class of upwind finite volume methods, namely Riemann solvers, and their applications in MHD, the definition, constituents, formation mechanisms and effects of space weather and some of the space missions that are and will be performed in its prediction. Secondly, detailed analysis of the compressible ideal MHD equations is given in the form of the derivation of the equations, their dimensionless numbers which will be of use to specify the flows in the following chapters, and finally, the presentation of the MHD waves and discontinuities, which indicates the complexity of the system of ideal MHD equations and therefore their further numerical analysis. The next discussion is about the main subject of the thesis, namely the solenoidal constraint satisfying techniques. First of all, the definition and significance of the solenoidal constraint is given. Afterwards, the most common solenoidal constraint satisfying techniques in the literature are reviewed along with their abovementioned drawbacks. Moreover, particular emphasis is given to the Powell's source term approach which was also implemented in the upwind finite volume MHD solver developed. In addition, the hyperbolic divergence cleaning technique is presented in detail together with the resemblance and differences between it and ACA. Some other solenoidal constraint satisfying techniques are briefly mentioned at this stage. After these, ACA is presented in the following way: The point of inspiration, which is the analogy made with Chorin's artificial compressibility method developed for incompressible CFD, the introduction of the modified system of ideal MHD equations due to ACA, the derivation of the wave equation governing the propagation of $ ablacdotvec{B}$ errors and the analytical consistency proof. Having finished the core discussion of the thesis, the solver developed and its constituents are given in the fourth chapter. Furthermore, a brief overview of the platform into which this solver was implemented, namely COOLFluiD, is also given at this point. Afterwards, a thorough numerical verification of the ACA approach has been made on an increasingly complex suite of test cases. The results obtained with ACA and Powell's source term implementations are given in order to numerically analyse and verify ACA and compare the two methods and validate them with the results from literature. The sixth chapter is devoted to further validation of ACA performed with a variety of more advanced space weather-related simulations. In this chapter, also the $vec{B}_{ extrm{0}} + vec{B}_{ extrm{1}}$ splitting technique used to treat planetary magnetosphere is presented along with its application to ACA and Powell's source term approaches. This technique is utilized in obtaining the solar wind/Earth's magnetosphere interaction results and is based on suppressing the direct inclusion of the Earth's magnetic field, which is a dipole field, in the solution variables. In this way, problems are avoided with the energy equation that could arise from the drastic change of the ratio of the dipole field and the variable field computed by the solver (i.e. $frac{lvertvec{B}_{ extrm{0}}lvert}{lvertvec{B}_{ extrm{1}}lvert}$) in the computational domain. Finally, conclusions and future perspectives related to the material presented in the thesis are put forward.

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