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Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 188-196). Available also in a digital version from Dissertation Abstracts.

We present new, accurate astrophysical parameters for both components of the six short-period Algol-type binary stars RZ Cas, AT Peg, TX UMa, AF Gem, RU UMi and HU Tau. The accuracy of the astrophysical parameters is ensured by the determination of a mass ratio for each of the systems from the spectroscopic orbits of both components via the cross correlation technique. For RZ Cas and AT Peg we have developed a simple technique to correct the observed photometry for the presence of the secondary component. Spectral classification of the primary component of AT Peg was aided by the use of an improved Doppler tomography technique. The systems RZ Cas, AT Peg, TX UMa, AF Gem and HU Tau are found to be apparently normal semi-detached Algol-type systems and accurate masses and radii have been determined with a typical precision of a few percent. For RU UMi we have been able to confirm the suspected semi-detached configuration. We have compiled a list of nine Algol-type binary stars, five from this study, for which the observed astrophysical parameters have been determined accurately using a combination of both spectroscopic and photometric data in a self-consistent solution. The general model of non-conservative case B evolution adequately explains the properties of these systems as a group. Angular momentum loss via a magnetic stellar wind is shown to be an important factor in the evolution of these systems. However, there appear to be no published evolutionary models which can be used to estimate the properties of the progenitors of these systems. For the more massive systems the best available models predict periods that are too large by ~50-250% and luminosities for the faint components that are too high by factors of 10-20.

Dans le cadre d’une contribution à la modélisation des caloducs oscillants, le modèle mis en place se résume à une bulle seule se déplaçant dans un tube de dimension capillaire.Une densité volumique de chaleur est considérée dans la paroi du capillaire, et la température de référence considérée n’est pas la température de saturation de la phase vapeur,mais la température extérieure au tube ce qui permet la variation de la température de saturation dans le temps et une meilleur adéquation du modèle avec la réalité. La résolution du modèle est effectuée par étapes selon la technique de perturbation du domaine,et les effets physiques de moindres importances peuvent être ajoutés au problème simplifié, en particulier les effets inertiels. Cette résolution a permis de définir une nouvelle corrélation portant sur la hauteur de film déposé par le bouchon liquide en mouvement en fonction du nombre capillaire et d’un nombre d’évaporation représentant l’intensité du chargement thermique. Ce modèle permettra aussi d’étudier l’influence réciproque des champs de vitesse et de température sur le bouchon de liquide devant le ménisque en déplacement. La résolution du problème associé à la partie arrière de la bulle met en évidence la formation d’un bourrelet de liquide entre le film de liquide déposé à la paroi et le ménisque arrière. La taille de ce bourrelet est fortement dépendante de la densité de flux de chaleur imposée à la paroi. Dans le cas o`u le ménisque arrière remouille un film adsorbé laissé à la paroi après assèchement du film, la ligne triple présente des ondulations axiales dues à son déplacement, et non au chargement thermique. La densité de flux de masse évaporée à l’interface liquide-vapeur entraîne une modification non seulement de la température de saturation, mais aussi de la masse de la bulle. Un modèle thermodynamique de la phase vapeur a ´et´e mis en place pour étudier les paramètres importants influençant les variations temporelles des caractéristiques géométriques et thermodynamiques de la bulle. / The model of a single bubble moving in a capillary tube is written as a contribution to the modeling of Pulsating Heat Pipes. A constant heat load is considered at the wall, and the reference temperature of the problem is defined to be the outside medium temperature, which is closer to reality, and thus allowing the saturation temperature of the vapor phase to vary. Using domain perturbation techniques, a step-by-step resolution ofthe model is implemented, allowing minor physical effects to be taken into consideration,for example the inertial effect on the receding meniscus. A new correlation is proposed on the thickness of the liquid film deposited by the receding meniscus, by means of the capillary number and an evaporation number representing the thermal condition. The velocity and temperature fields in the liquid plug ahead of the meniscus can also be obtained. The resolution of the problem associated with the rear-end of the bubble,where the rear meniscus advances on either a micrometric liquid film or an adsorbed film left by the dry-out of the capillary wall, shows a corrugating liquid-vapor interface.The magnitude of these corrugations is strongly dependent on the value of the heat load applied at the wall. In the case of wall rewetting, the interface corrugations at the triple line are due to its displacement, and not to the thermal boundary condition. Because the evaporative mass flux through the liquid-vapor interface modifies the vapor bubble mass, a complete transient thermodynamical model of the bubble is implemented. In this case, the important parameters controlling the kinematics, dynamics and thermodynamics of the bubble were identified.

Please read the abstract in the dissertation. / Dissertation (MSc)--University of Pretoria, 1965. / gm2014 / Electrical, Electronic and Computer Engineering / Unrestricted

M.Sc. / This project involves the analysis of data obtained through membership of the Kepler Asteroseismic Science Consortium Working Group 9, viz. proprietary data received from the Kepler Space Telescope. In this work, Kepler data on KIC011175495 are de-trended, and subject to a lengthy iteration of refined and sophisticated analysis routines, using many software platforms based on sound physical principles. The iteration is shown to converge to final values for the binary parameters and the pulsation frequencies present in the system. Conclusions are made on the interpretation of these results and the way forward for further analysis of this and related systems.

Ce document propose une démarche expérimentale permettant de reproduire les écoulements pulsés, que l’on retrouve dans le collecteur d’échappement d’un moteur, sur les caractéristiques des performances d’un turbocompresseur de suralimentation. Une étude comparative des différents moyens d’essais existants, permettant de reproduire les effets pulsés en entrée de la turbine d’un turbocompresseur, est présentée. Elle permet d’évaluer les avantages et les inconvénients de chacun pour définir un cahier des charges de fonctionnalité d’un nouveau banc d’essai Les travaux permettant la mise en oeuvre de l’instrumentation spécifique propre à répondre aux besoins de développement de ce moyen d’essai sont exposés. Le principal objectif est pouvoir obtenir une mesure du débit instantané ainsi que celle de la température instantanée. Les premiers résultats obtenus avec les conditions d’essais utilisant le système mis en place pour simuler le régime pulsé, complétés par une analyse des différentes procédures d’exploitation, montrent qu’il est possible de restituer des essais cohérents en régime d’écoulement stationnaire et pulsé afin de les comparer. Les possibilités d’exploiter d’autres résultats sont évoquées, compte tenu de la flexibilité du banc ; il est en effet possible faire varier de façon indépendantes plusieurs types de conditions d’écoulements pulsés pour simuler, par exemple, différents points de charge d’un moteur donné ou de simuler différentes valeurs du nombre de cylindres. / The document presents the results of an experimental work devoted to create pulse flows, independently from a real car engine, equivalent to the exhaust pipe engine flow characteristics, on the overall performances of a turbocharger. A comparative analysis on existing test stands that are able to perform such flow conditions is presented. This allows defining a new test stand which specific conditions that are not already covered by previous test stands. All steps concerning the ability to set up of the new test stand and more specifically instrumentation development and acquisition systems are detailed. First set of results obtained with the test stand, in pulse conditions, are presented with some analysis on performance comparisons between steady and pulse inlet conditions at the turbocharger inlet section. The new pulse test stand allows performing more flexible variations of inlet flow unsteady conditions, different thrust load values and number of motor cylinders as well

A numerical study was carried out for enhanced heat transfer from two heated blocks in a pulsating channel flow by porous heat sink. The flow over the fluid region is governed by the Navier-Stokes equation, and the flow through the porous medium is governed by the Darcy-Brinkman-Forchheimer equation. These two flows are coupled through the interface boundary conditions at the porous/fluid and porous/solid interfaces. After a stream function-vorticity transformation, solution of the coupled governing equations for fluid/porous/solid composite system is obtained using the control-volume-based procedure and hybrid scheme. Comprehensive time-dependent flow and temperature data obtained and averaged over a cycle of pulsation in a periodic steady state. In addition, this study details the effects of variation in the governing parameters, such as inertia parameter, Dracy number, Reynolds number, Strouhal number, pulsation amplitude and geometric parameters, to illustrate important fundamental and practical results. The results show that the periodic change of shape of interblock recirculation flow caused by porous-covering blocks has significant enhanced effect on flow pattern and heat transfer characteristics. This enhanced effect is found to increase with Reynolds number, Strouhal number and pulsation amplitude but decrease with Dracy number. In comparison with the non-porous heat sink case for a steady non-pulsating flow, significant increases in the average Nusselt number are predicted and the instantaneous maximum temperatures within the heated block array are reduced. Moreover, it is shown that specific choices in certain geometric parameters, such as interblock space, can make pronounded change in the cooling of heated block.

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