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No description available.

No description available.

This thesis is concerned with the steering and manoeuvring of surface ships. Recent developments in hull design have seen the introduction of the pram stern. This hullform has proved less directionally stable than more conventional stern shapes. Recent theoretical developments include the effect of stern vortices in a slender-body treatment of the ships hull. The inclusion of these vortex effects explains the discrepancy between the distribution of force and moment coefficients along a hull obtained experimentally compared to those determined using slender body theory alone. As yet this approach requires the position and strength of the shed vortices to be determined by other means. The theory also offers a means of explaining the relative instability of the pram stern. An experiment has been designed to directly test some of the predictions of this theory. The experiment entailed oblique towing of a set of 7 hullforms with segmented stern sections. The first group of five models are based on the British Bombardier with a variety of conventional and pram stem configurations. The remaining models were based on a simple elliptic hullform. The experiments provide detailed data of the longitudinal distribution of force and moment sway derivatives of the stem regions of these models. The experimental evidence provided support for the theoretical predictions, although some results were inconclusive because of the effect of additional flow phenomena. The physical insight provided by the generalised slender body theory has generated the impetus to use a semi-empirical approach to predict the manoeuvring derivatives from basic hull geometry. The equations developed for the linear velocity derivatives use predictors based on the physical phenomena and are formulated to recognise the interdependency of these derivatives. The new equations are statistically more satisfactory than previous analyses of this type.

Graduation date: 1993

The movement of organisms and resources within ecosystems are essential elements in the productivity, stability, and distribution of communities. This thesis examines how water velocity, a defining factor of lotic systems, influences the dispersion of benthic organisms and particulate organic matter in small stream ecosystems. Variation in movement-related behaviours in two rheophilous (‘flow-loving’) mayflies (Epeorus and Baetis) and two rheophobic (‘flow-avoiding’) mayflies (Ameletus and Paraleptophlebia) were compared to determine how benthic organisms disperse between and within habitat patches in hydrodynamically complex landscapes. The degree to which water velocity and particle shape influence the retention of organic matter (including deciduous leaves, conifer needles, red-cedar fronds, and branch fragments) was examined to determine how physical factors determine detrital resource availability in streams. Although water velocity did not influence the crawling rates of Baetis and Ameletus in daylight conditions, both mayflies dispersed rapidly upstream in low-velocity flows in dark conditions. Drift rates of both mayflies were lower in daylight than dark conditions, and were generally inversely related to their habitat preferences. Escape responses in grazing Epeorus, Baetis, and Ameletus larvae in a range of flow conditions showed that retreat distance was more sensitive than flight initiation distance to variation in water velocity, suggesting that hydrodynamics mediate the risks of predation and the costs of flight in stream systems. Comparisons of the transport distances of live larvae, dead larvae, and passive tracer particles in low and high water velocities showed that drift distance varied substantially among taxa, and that behavioural control over drift distance generally declined as water velocity increased. While organic matter particles generally travelled further in high-velocity reaches, leaves were retained in riffles when they impacted on protruding clasts, while ‘stiff’ particles were retained when they settled into streambed interstices. Leaves placed in high-velocity microhabitats were broken down more slowly than leaves in low-flow areas, likely due to the exclusion of large-bodied detritivores. In conclusion, this thesis supports the view that hydrodynamic forces control trophic interactions and local population dynamics in stream ecosystems by directly altering the physical – and sometimes behavioural – processes of particle entrainment, transport, and deposition.

In the pulp and paper industry, the interaction between the gas, liquid, and solid phases occurring in various unit operations is often not clearly understood. Such multi-phase operations include flotation deinking (a separation process of paper fibres in the recycling process) as well as the delignification and bleaching operations in the kraft pulping process. Much of the design, operation, and optimization of such processing equipment are dependent upon past experience as well as trial-and-error methodologies. Pulp fibre suspensions possess a complex and unique rheology. The unpredictability of the behaviour of pulp suspensions at any given mass concentration is due to the bonding between the fibres resulting in network formation (which depends on suspension consistency) with this interaction creating complexity in fluid flow in various unit operations. This thesis describes the gas hydrodynamic behaviour and gas-liquid mass transfer characteristic in low- and medium-consistency pulp suspensions in batch operation. First, the hydrodynamic behaviour of the gas phase (air) in water and pulp suspensions having mass concentrations up to Cm = 7% is examined by visually observing and recording the bubble shape, size, and rise velocity in a rectangular channel. Results are obtained using a high-speed video camera. Second, the hydrodynamic behaviour is described in terms of the gas holdup along with axial and radial gas phase distributions in water and kraft pulp suspensions having mass concentrations between Cm = 0.5 and 9% in a batch-operated cylindrical bubble column. The gas holdup results are compared using three methods: the suspension height method, the pressure difference method, and the electrical resistance tomography (ERT) method. Finally, the volumetric gas-liquid mass transfer characteristic of air in water and kraft pulp suspensions having mass concentrations up to Cm = 4% is examined in the same bubble column in batch-operation using a dissolved oxygen probe. Experimental results were comparable to that in literature for water and for pulp fibre suspensions having Cm < 2%. The presence of fibres had a significant effect on the gas holdup and mass transfer characteristic with results providing insight on the limitations that exist in industrial pulp unit operations.

Thesis (PhD)--University of South Australia, 2004.

Thesis (M.S.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Otto Stein. Includes bibliographical references (leaves 41-43).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaf 113). Also available via the Internet.