No description available.

No description available.

Large amplitude interfacial waves are an important feature of annular gas-liquid two-phase flow. They act as a source of entrainment for liquid droplets. They occur for liquid flow rates above a critical value which depends on the gas flow rate. This thesis examines the formulation of a mathematical model to describe the behaviour of these nonlinear waves. Attention is focussed on the case of vertical upwards flow with reference to the experimental conditions for the rig at AERE Harwell. A comprehensive account is given of the limitations and similarities of mathematical models proposed by earlier research workers and their applicability to vertical two-phase flow. The most suitable approaches are found to be kinematic wave theory and an integral method. Experiments have been carried out at AERE Harwell to determine the relationship between liquid flux and film thickness required by kinematic wave theory and also to test some of the theory's predictions. There is a discussion of the difficulties involved in modelling the stresses exerted by the turbulent gas core on disturbance waves. The applicability of Benjamin's 'quasi-laminar' theory is considered. A linear stability analysis indicates that the interface is always unstable. The linear theory cannot provide a criterion for disturbance wave inception. Alternative explanations for wave inception are suggested. The SMAC (Simplified Marker And Cell) numerical method has been developed to model the time dependent behaviour of large amplitude waves in vertical annular two-phase flow. Finally, it is proposed that any realistic mathematical model for disturbance waves should be based upon kinematic wave theory and should take account of wave-breaking.

The work reported in this thesis falls into three distinct, though intimately related parts. Part I is concerned with the production of a variable temperature two-phase flow test facility for studying single and two-phase flows around arbitrary two-dimensional bodies. It includes the initial design study required to define an operational envelope for the facility, and the design and constructional features of its main components and ancilliary systems. The design of a two-phase flow vapour ventilation experiment is described, together with the operating procedure for the facility. Part II reports single and two-phase experiments with a two-dimensional circular cylinder, the two-phase flows being generated by inducing natural cavitation. The cavitation inception flow regime was found to be strongly influenced by viscous effects. Three forms of incipient cavitation were observed, two attached or very close to the cylinder surface, and one of a detached nature, occurring well downstream in the wake of the cylindrical test body. These inception modes have been related to the fully wetted viscous flow around the cylinder in the Reynolds number range 10⁵ <R_d<10⁶. The development of cavitation from these three aforementioned incipient states was investigated. Viscous effects were found to influence both the limited and developed cavitation flow regimes. For development of cavitation at Reynolds numbers corresponding broadly to the supercritical range for fully wetted flow, a critical cavitation number was found at which the apparent free stream lines of the flow changed from a concave to a convex disposition. For the experimental configuration used, this critical cavitation number was independent of Reynolds number, for Reynolds numbers above the critical value. With development of cavitation at Reynolds numbers corresponding broadly to the subcritical range for fully wetted flow, no such gross changes in flow pattern were observed, the displacement of the apparent free streamlines of the flow between the limited and fully developed cavitating states being minimal. Part III contains recommendations for modifications to the experimental facility and suggestions for further studies arising from the results reported herein.

No description available.

Abnormal pressures have been measured in the deep boreholes at the Bruce site, southern Ontario, where a deep geologic repository for low and intermediate level radioactive waste disposal has been proposed. The pressure regime in the stratigraphic units exhibits either higher than hydrostatic pressure (over-pressured) or lower than hydrostatic pressure (under-pressured) are considered to be abnormal. At the Bruce site, the Ordovician sediments are under-pressured while the underlying Cambrian sandstone and the overlying Guelph carbonate are over-pressured. Hypotheses have been documented in literature to explain the phenomenon of abnormal pressures. These hypotheses include osmosis, glacial loading and deglaciation unloading, exhumation of overlying sediments, crustal flexure and the presence of an immiscible gas phase. Previous work on the Bruce site has shown that the under-pressures in the Ordovician limestone and shales could not be explained by glaciation and deglaciation or by saturated analyses. The presence of a gas phase in the Ordovician formations has been determined to be a reasonable cause of the under-pressure developed in the Ordovician shales and limestones at the Bruce site. Support for the presence of a gas phase includes solution concentrations of methane, concentrations of environmental isotopes related to methane and estimates of water and gas saturations from laboratory core analyses. The primary contribution of this thesis is the sensitivity analyses performed on the hydrogeologic parameters with respect to a one dimensional two-phase flow model. First, a one dimensional two-phase air and water flow model was adopted and reconstructed to simulate the long-term evolution of the groundwater regimes at the DGR site. Then the hydrogeologic parameters which impact the presence of under-pressure in the groundwater are investigated. Data required to quantify the properties of geologic media and groundwater are adopted directly from borehole testing and laboratory testing results. The permeable boundaries of the domain are assumed to be water saturated and pressure specified (using hydrostatic conditions in the Guelph Formation and hydrostatic with 120 m over-pressure condition in the Cambrian and Precambrian). Isothermal conditions were assumed, thus constant water density and viscosity values are estimated for the average total dissolved solids (TDS) concentration of the modelled stratigraphic column. A constant diffusion coefficient (a diffusivity of $0.25\times10^{-8}$ m$^2$/s) of air in water is assumed with a saturation-dependent tortuosity. The air generation rate is assumed to simulate the gas phase generated in the Ordovician formations. The numerical simulation of up to 4 million years provides a means to explore the behaviour of gas phase dissipation due to partitioning into the water phase and diffusive transport in the solute phase. Results confirmed that the presence of a gas phase would result in the under-pressure in water.

Thesis (Ph. D.)--University of Adelaide, Dept of Mechanical Engineering, 1987. / One microfilm reel (16 mm.) in pocket. Includes bibliographical references (leaves 194-201).

Thesis (Ph.D.) -- McMaster University, 1999. / Includes bibliographical references (leaves 222-229). Also available via World Wide Web.

Thesis (Ph. D.)--Ohio University, 2001. / Title from PDF t.p.

Thesis (Ph.D.)--University of Tulsa, 1974. / Bibliography: leaves 89-91.