Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (Ph. D.)--University of Washington, 1993. / Vita. Includes bibliographical references (leaves [131]-137).

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: A.D. Kirwan, College of Earth, Ocean, & Environment. Includes bibliographical references.

Thesis (M. Sc.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 106-112.

Thesis (M.S.) -- Central Connecticut State University, 2005. / Thesis advisor: Daniel Larose. "... in partial fulfillment of the requirements for the degree of Master of Science in Data Mining." Includes bibliographical references (leaves 30-31). Also available via the World Wide Web.

abstract: A numerical study of incremental spin-up and spin-up from rest of a thermally- stratified fluid enclosed within a right circular cylinder with rigid bottom and side walls and stress-free upper surface is presented. Thermally stratified spin-up is a typical example of baroclinity, which is initiated by a sudden increase in rotation rate and the tilting of isotherms gives rise to baroclinic source of vorticity. Research by (Smirnov et al. [2010a]) showed the differences in evolution of instabilities when Dirichlet and Neumann thermal boundary conditions were applied at top and bottom walls. Study of parametric variations carried out in this dissertation confirmed the instability patterns observed by them for given aspect ratio and Rossby number values greater than 0.5. Also results reveal that flow maintained axisymmetry and stability for short aspect ratio containers independent of amount of rotational increment imparted. Investigation on vorticity components provides framework for baroclinic vorticity feedback mechanism which plays important role in delayed rise of instabilities when Dirichlet thermal Boundary Conditions are applied. / Dissertation/Thesis / M.S. Mechanical Engineering 2011

Current stoichiometric spark-ignited engine technologies require costly catalytic converters for reductions in tailpipe emissions. Load control is achieved by using a throttle, which is a leading contributor to reductions in efficiency. Spark-ignited lean burn natural gas engines have been proven to be more efficient and emit fewer pollutants than their stoichiometric counterparts. Load reduction in these engines can be achieved by regulating the air/fuel ratio of the intake charge thereby reducing the efficiency penalties inherent to throttling. Partially stratified charge (PSC) can provide further reductions in emissions and improvements in efficiency by extending the lean limit of operation. PSC is achieved by the ignition of a small quantity of natural gas in the vicinity of the spark plug. This creates an easily ignitable mixture at the spark plug electrodes, thereby providing a high energy ignition source for the ultra-lean bulk charge. Stratified charge engine operation using direct injection (DI) has been proposed as a method of bridging the throttleless load reduction gap between idle and ultra-lean conditions. A previous study was conducted to determine if PSC can provide a high-energy ignition source in a direct injected stratified charge engine. Difficulties with igniting the PSC injections in an air-only bulk charge were encountered. This study focuses on a fundamental Schlieren image-based analysis of PSC combustion. Natural gas was injected through a modified spark plug located in an optically accessible combustion bomb. The relationships between PSC injection timing, fuel supply pressure and spark timing were investigated. Spark timing is defined as the duration between commanded start of injection and the time of spark. As the fuel supply pressure was increased, the minimum spark timing that lead to successful combustion also increased. The largest spark timing window that led to successful combustion was determined to be 80 ms wide at an injection fuel supply pressure of 300 psi. The amount of unburned natural gas increased with increasing spark timing. A cold flow study of the PSC injection system was also conducted. The PSC injection solenoid was found to have a consistent average injection delay of 1.95 ms. The slope of the linear response region of observed injection duration to commanded injection duration was 8.4. Due to plenum effects, the average observed injection duration of the entire PSC system was an order of magnitude longer than the commanded injection duration and was found to vary significantly with fuel supply pressure. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The water in most reservoirs is density stratified with depth. This stratification leads to the inhibition of vertical movement, consequently, when water is withdrawn from the reservoir it tends to move in a jet-like layer called a withdrawal layer, towards the sink. By placing the sink at a certain depth, one is able to selectively withdrawal water from a limited range of depths and thus obtain water of a desired quality. Much work has been done in this field by considering a simplified boundary geometry, usually rectangular. However little attention has been given to the effects of accurate boundary geometry. For this thesis, five numerical experiments were conducted for the problem of a two-dimensional, viscous, incompressible, slightly-stratified flow towards a sink in a triangular reservoir. / Science, Faculty of / Mathematics, Department of / Graduate

Internal waves are generated in a fluid if the density increases continuously with depth. The variation in density with depth, or stratification, defines the natural frequency of the fluid N. Two common examples of stratified fluids are the ocean and atmosphere; internal waves are generated continuously in both mediums. Although there are many internal wave generation mechanisms, one common and frequently studied method is tidal flow over oceanic bathymetry. If the local natural frequency of the water near the topography is greater than the tidal frequencyω, internal waves will be generated by the tidal flow over the topography. If N=ω, only evanescent waves will be formed. Unlike internal waves, evanescent waves decay rapidly as they move vertically away from their generation site. As evanescent waves pass from an evanescent region (N=ω),through a turning depth (N=ω) and into a propagating region (N=ω), they become propagating internal waves. Because internal waves can propagate energy across large distances, they play an important role in oceanic mixing and the overall energy budget of the ocean. Knowing where these waves are formed from evanescent waves and their corresponding energy improves understanding of the impact on their surrounding area.Kinetic energy density of evanescent and internal waves formed from oscillatory flow over topography in evanescent regions is first estimated using synthetic schlieren experiments and a novel linear theory model. Experiments were performed with two Gaussian topographies in an exponential density profile. The linear theory model, which uses a set of equations that links the evanescent and propagating regions with the Airy function to overcome the discontinuity inherent with a turning depth, was compared to the experiments. Both methods showed that increasing Fr1,the strength of the evanescent region relative to the excitation frequency, causes the propagating kinetic energy to decrease. In addition, kinetic energy decreased with increasing distance between the topography and the turning depth. Because the model does not account for non-linearities such as turbulence generation, it regularly overestimates propagating kinetic energy relative to the experiments. After comparing the model with synthetic schlieren experiments, it was used to estimate that 25% of the evanescent wave energy generated by an oceanic topography located at 15◦N, 130◦E can become propagating wave energy.The influence of topography shape and fluid density profile on kinetic energy density was also explored through a combination of experiments, a linear theory model, and numerical simulations. From numerical simulations, kinetic energy can be directly calculated with the velocity pro-file and indirectly with the density perturbation field, in the same manner as the synthetic schlieren experiments. Average propagating internal wave kinetic energy (KE∗ 2) as a function of Fr1D/H,which combines Fr1 with the relative distance between the topography and the turning depth D/H,was compared for all methods. KE∗ 2 decreases with increasing Fr1D/H for all methods. Also, far from the turning depth, the direct and indirect simulations indicate similar kinetic energy when in the propagating region, where a distance from the turning depth can be quantified based on N and ω. This work was expanded to include a medium Gaussian, steep Gaussian, sinusoidal, and complex topography with two layer linear, parabolic, cubic, and exponential density profiles to investigate the validity of assuming an average natural frequency in the evanescent region and the impact of the topographic slope on KE∗ 2. A comparison of the density profiles indicated that using a two layer linear density profile has similar results compared to the other density profiles for estimating KE∗ 2 as a function of Fr1D/H. Also, KE∗ 2 is non-negligible for Fr1D/H<4. Increasing the maximum slope of a topography shape decreases the kinetic energy of the generated internal waves, though it was found that the energy is dependent upon the actual shape of the topography as well.Particle image velocimetry (PIV) experiments were performed and compared to synthetic schlieren (SS). While SS experiments generally resulted in an overestimate of kinetic energy relative to the PIV results, the trends from each experimental method matched well. It is recommended that SS be used in regions away from turning depths, but that either are valid in the evanescent and propagating regions. PIV methods should be used when results near the turning depth or the topography are desired.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21366号 / 工博第4525号 / 新制||工||1705(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 花崎 秀史, 教授 黒瀬 良一, 教授 稲室 隆二 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM