No description available.

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.

No description available.

Enhancing the performance of mixing and fluid entrainment by excitation of quasi-steady jets has been a subject of research for more than three decades. During the 1980s a special emphasis was placed on mechanically oscillating planar jets and the possibility to augment thrust of V/STOL aircraft. However, during this time, little attention was paid to the classification of flow regimes, the development of coherent structures or the existence of different regions in the flow within the jet near field. For the present study, a large aspect ratio nozzle was oscillated in the direction transverse to the width of the nozzle in simple harmonic motion. For a constant nozzle height, the stroke length, oscillation frequency and jet velocity were systematically varied. Over 240 flow cases were examined using a novel method of phase-locked flow visualisation. Following an initial analysis of the acquired data, a small subset of flow conditions was selected for further quantitative investigation using Particle Image Velocimetry (PIV). The phase-locked flow visualisation led to the identification and classification of three separate flow regimes, the Base Flow, the Resonant Flow and the Bifurcation Flow Regimes. Each regime is linked to the other regimes by the presence of a small number of repetitive coherent structures in the form of starting and stopping vortices. The analysis revealed a relationship between the stroke-to-nozzle height ratio and the ratio of the forcing frequency to the natural vortex shedding frequency in the planar jet. This directly contradicts the relationship between the Strouhal and Reynolds numbers of the jet that was proposed by previous investigators. Comparison of phase-locked PIV and flow visualisation data confirms both, the validity of the new regime classification and the identification of relevant large-scale structures. Time-averaged vorticity data are also used to further illustrate the differences between the three flow regimes. Investigation of the time-averaged qualitative data for the Base and Resonant Flow Regimes show that three distinct flow regions exist within both regimes. Adjacent to the nozzle is the initial formation region, where all large-scale structures form. This is followed by a coherent near-field region in which the jet exhibits very little spread for both the Base and Resonant Flow Regimes. Within this region no pairing of the large-scale vortices from the opposing sides of the flow can be found. This region is followed by a transition region that is marked by the sudden breakup and dissipation of all visible large-scale coherent structures. The vortex formation distance is then investigated using the available PIV data and compared with the results of previous investigations. The data show that the formation distance depends on the jet velocity, oscillation frequency and the stroke length. The agreement with previous data is poor due to differences in the method of measurement. Quantitative data are also used to investigate the centreline velocity decay in relation to changes of the jet Reynolds number and stroke-to-nozzle height ratio. The results show that the velocity decay rate increases with increasing stroke length as is expected from findings of earlier studies. In addition the centreline velocity decay rates in the mean jet transition region appear to be constant for each stroke length in the cases examined. Finally, conclusions are drawn and recommendations for future work are presented. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349701 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2009

Enhancing the performance of mixing and fluid entrainment by excitation of quasi-steady jets has been a subject of research for more than three decades. During the 1980s a special emphasis was placed on mechanically oscillating planar jets and the possibility to augment thrust of V/STOL aircraft. However, during this time, little attention was paid to the classification of flow regimes, the development of coherent structures or the existence of different regions in the flow within the jet near field. For the present study, a large aspect ratio nozzle was oscillated in the direction transverse to the width of the nozzle in simple harmonic motion. For a constant nozzle height, the stroke length, oscillation frequency and jet velocity were systematically varied. Over 240 flow cases were examined using a novel method of phase-locked flow visualisation. Following an initial analysis of the acquired data, a small subset of flow conditions was selected for further quantitative investigation using Particle Image Velocimetry (PIV). The phase-locked flow visualisation led to the identification and classification of three separate flow regimes, the Base Flow, the Resonant Flow and the Bifurcation Flow Regimes. Each regime is linked to the other regimes by the presence of a small number of repetitive coherent structures in the form of starting and stopping vortices. The analysis revealed a relationship between the stroke-to-nozzle height ratio and the ratio of the forcing frequency to the natural vortex shedding frequency in the planar jet. This directly contradicts the relationship between the Strouhal and Reynolds numbers of the jet that was proposed by previous investigators. Comparison of phase-locked PIV and flow visualisation data confirms both, the validity of the new regime classification and the identification of relevant large-scale structures. Time-averaged vorticity data are also used to further illustrate the differences between the three flow regimes. Investigation of the time-averaged qualitative data for the Base and Resonant Flow Regimes show that three distinct flow regions exist within both regimes. Adjacent to the nozzle is the initial formation region, where all large-scale structures form. This is followed by a coherent near-field region in which the jet exhibits very little spread for both the Base and Resonant Flow Regimes. Within this region no pairing of the large-scale vortices from the opposing sides of the flow can be found. This region is followed by a transition region that is marked by the sudden breakup and dissipation of all visible large-scale coherent structures. The vortex formation distance is then investigated using the available PIV data and compared with the results of previous investigations. The data show that the formation distance depends on the jet velocity, oscillation frequency and the stroke length. The agreement with previous data is poor due to differences in the method of measurement. Quantitative data are also used to investigate the centreline velocity decay in relation to changes of the jet Reynolds number and stroke-to-nozzle height ratio. The results show that the velocity decay rate increases with increasing stroke length as is expected from findings of earlier studies. In addition the centreline velocity decay rates in the mean jet transition region appear to be constant for each stroke length in the cases examined. Finally, conclusions are drawn and recommendations for future work are presented. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349701 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2009

Thesis (M.S. - Geosciences)--University of Arizona, 1983. / Includes bibliographical references (leaves 136-140).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1984. / Includes bibliographical references (leaves 84-87).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 183-184).

Thesis (M.S.)--University of Nevada, Reno, 2007. / "August 2007." Includes bibliographical references (leaves 81-85). Online version available on the World Wide Web.