Turbulent flows are encountered in nearly every case where fluid motion is involved. Turbulent flow in pipes is of great practical interest, and the problem of flow in the entry region is of special importance since the great majority of applications are in the realm of developing flow.

When entering into the subject of turbulent flow, it is essential to understand that the kind of flow with which we deal belongs to a particular class known as shear flow. These types of flow comprise flow fields in which relative velocities have been induced by shear stresses rather than by the action of pressure forces. In pipe flow, when the fluid enters through the well-rounded bell from a reservoir or from the calm open air, a uniform velocity distribution occurs at the pipe entrance. Immediately down stream from the entrance of the pipe, the flow is structured with a boundary layer near the wall, and is of uniform velocity profile in the central part. Due to the action of wall friction, the boundary layer grows thicker and thicker downstream. As the mass flux is constant throughout the pipe,’ the central stream must accelerate to compensate for this retardation of the flow near the wall. Finally, the boundary layer thickness reaches the value of pipe radius. The free stream, therefore, disappears from the central part of the pipe. Furthermore, Barbin and Jones (1)* pointed out that following the disappearance of the free stream, further changes in the velocity profile and turbulence structure occur before a fully developed condition is reached* The flow in the inlet region of a pipe is, therefore, a transition from a boundary layer type flow at the entrance to a fully developed flow downstream. The change of the free stream velocity in the entry region causes a greater reduction of the static pressure than that in the fully developed region.

The purpose of this thesis was to study the influence of manufacturing variations on gear performance. The manufacturing variations inherent in different manufacturing methods were studied to include the effect of real surfaces. Real surfaces have surface irregularities at least on some scale, which can significantly influence how loads are transmitted at the gear contact. To some extent, the lubricant design can help to prevent contact that could lead to tooth failures by forming a protective surface boundary layer. An experimental study was used to consider the compositions of these layers with a surface analysis method. In Paper A a robust design approach was used to find out to what extent the current standard for calculation of surface durability treats manufacturing variations and the choice of lubricant. The results show that the simplest calculation method used is not enough to predict the effect of these on surface durability. Additionally, the standard quality levels are poorly incorporated in the standard calculating procedures for surface durability, and the quality of the gear tooth is restricted to include only a few parameters. In Paper B a pin-on-disc machine was used to evaluate the tribofilm formation by the additives and the corresponding wear occurring in the boundary lubrication regime in environmentally adapted lubricants. Studies of the additive and base fluid interaction were carried out using glow discharge-optical emission spectroscopy. It was found that the chemically reacted surface boundary layers played an important role in terms of wear. More specifically, the oxide layer thickness had significant influence on wear. The findings also demonstrate the complexity of lubrication design formulations coupled to these layers. For example, it was found that the pre-existing surface boundary layer (before any lubricant had been added) played an important role in allowing the lubricant to react properly with the surfaces. The aim of Paper C was to contribute to the knowledge of how different surface topographies, tied to manufacturing methods, influence the early life contact conditions in gears. Topographical measurements of differently manufactured tooth flanks were used as data input to a contact analysis program. The variation in surface topography inherent in the manufacturing method was found to have a strong influence on the contact area ratio.

This work aims to examine the complexity of the current turbulent relationship between Slovakia and Hungary and its influence on the system of Carpathian states. The work is based on the Gérard Dussouy"s (2010) and Gyula Csurgai"s (2009) new geopolitical approach and offers a systemic, dynamic and interdisciplinary analysis of the development in Carpathian basin. The work indentifies the key factors that are feeding the Slovak-Hungarian relations. Consequently, it offers further prospectives of these relations and their reflection within the Carpathian Basin. Moreover, the analysis enables measuring of further development of the Carpathian region.

Includes bibliographical references / This dissertation seeks to explore the core drivers of international cooperation over shared water courses particularly in Southern African, using the example of the Okavango River Basin as a case study. As a starting point it highlights the hydro-political context of Southern African, which is dominated by more than 21 shared water courses and faces significant challenges to its water sector namely through climate variability and population growth. In light of these pressing issues which could create a security complex for sovereign riparian states, international cooperation over trans-boundary water sources is imperative. Drawing on core theories of international relations, this dissertation suggests that cooperation between riparian states is a result of strong institutional frameworks, at a river-basin, regional and international level. Cooperation is further reinforced through development functionalism which plays an important role in facilitating cooperation through the advancement of regional development goals and initiatives. Finally, the dissertation explores the role of international norms of cooperation over trans-boundary water courses and the important role they play in fostering cooperation. Using the case of the Okavango River Basin, the dissertation suggests that in Southern Africa, the strongest driver of cooperation is strong legal and institutional frameworks, which once established, form the basis for sustainable cooperation for water diplomacy between riparian states. Cooperation over the Okavango River Basin and the twenty years of cooperation established between Angola, Namibia and Botswana through the Permanent Cubango-Okavango River Basin Commission (OKACOM) highlights an optimistic account for hydro-political cooperation over trans-boundary water systems between sovereign riparian states and provides a useful model for water basin agreements that are yet to be established. This thesis thus concludes that in light of the growing challenges facing the water sector in Southern Africa, strong institutions and legal frameworks are required to enhance cooperation among riparian states.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1968. / Vita. / Bibliography: leaves 109-117. / by Rory Thompson. / Ph.D.

This study explores the boundary-work accomplished by seventeen female and male escort workers. Escort work, defined as the acceptance of money for spending time with and offering companionship to others, is not illegal; however, social scientific research indicates that escort workers often engage in paid sexual activity, thus placing their occupation within the realm of prostitution. Previous research indicates that escort workers, subsumed within the highest echelon of the prostitution hierarchy, are less likely than their street and brothel counterparts to report victimization and stigmatization, and are more likely to earn higher wages and use safe-sex practices. In light of these significant variations in work-related experiences, I use the boundaries framework and study boundary-work accomplished by the participants in an attempt to avoid perpetuating negative labels associated with escort work. I define boundary-work as the process by which individuals create symbolic distinctions between themselves and others, and the individualized process of structural boundary negotiation. Individuals play a significant role in the processes of group inclusion and exclusion through the creation of symbolic boundaries; they also must negotiate structural boundaries, such as laws and stereotypical gender roles. Thus: the study of boundary-work provides a means for social scientists to engage in intra- and inter-group comparisons among "deviant" and "non-deviant" individuals. Through in-depth interviews with nine female and eight male escort workers, I identified the symbolic boundaries they used to distinguish themselves from others. In addition to the identification of socio-economic, cultural and moral boundaries used as criteria for inclusion in and exclusion from their personal and professional lives, this study also identifies various strategies used to negotiate one structural boundary: criminal law. In addition, this study provides support for rational choice theory, as all of the participants viewed escort work as a chosen profession, and each participant believed the benefits outweighed the real costs and potential risks associated with escort work. Future research needs to (1) tease out the structural elements of boundary-work, (2) use a measure of relative saliency among symbolic boundaries, and (3) collect data regarding boundary-work accomplished by members of assumed "deviant" and "non-deviant" groups, in order to address basic assumptions of deviance.

The research on transition in supersonic and hypersonic boundary layers has been reinvigorated in the last decades because of the increased interest in high-speed flight. The receptivity to environmental disturbances of high-speed boundary layers developing over flat plates or curved surfaces is a very important problem because the transition process is directly impacted by it. The main objective of the research is to determine the effect of small steps on laminar high-speed boundary-layers that are excited by freestream disturbances in the form of vorticity and acoustic waves. Both supesonic and hypersonic regimes are analyzed using a high-order compressible Navier-Stokes numerical algorithm. It is found that both the backward and the forward steps are capable of stabilizing the disturbances that propagate inside the boundary layer. This will potentially delay the formation of three-dimensional disturbances that are precursors to transition into turbulence.

Görtler vortices develop in boundary layer flows over concave surfaces due to the imbalance between centrifugal forces and the wall-normal pressure gradient. These vortices can be efficient precursors to transition in boundary layers exposed to free-stream disturbance or surface non-uniformities, because they can alter the mean flow causing the laminar flow to breakdown into turbulence. In this thesis, a control technique aimed at reducing the energy associated with Görtler vortices that develop in supersonic boundary layers is introduced and tested. The control algorithm is based on distributed blowing and suction, with sensors placed either in the flow or at the wall. The result show that there is a dependence between the efficiency of the control algorithm and the spanwise separation of the vortices, that is the energy reduction is more significant for larger spanwise separations. The efficiency of the control algorithm seems to be insensitive to the variation of the Mach number.

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