The present thesis is a comparative study of the hydrodynamic effects of a few deterministic microasperity shapes in a thrust slider application. Numerical study based on finite difference methods is used to find the trend of important tribological properties such as friction and leakage. Also, this work utilizes a distinctive and practical approach for comparison by considering constant load conditions, instead of constant film thickness, as is expected in an operating thrust bearing. The results are encouraging and clearly reveal the existence of a transition point for asperity area fraction where a reversal in trends for both the coefficient of friction and leakage is observed. The shapes of asperities affect leakage but, have a negligible effect on coefficient of friction; however, the size and the type of asperity (positive or negative) do influence it. The effects of orientation, on the other hand, are found both on the coefficient of friction and leakage. Triangular asperities exhibit an advantage over the other shapes in terms of leakage. In general, the impact of shapes is distinguishable, more at higher asperity area fractions in accordance with the geometrical differences.

Granular Activated Carbon (GAC) is used in packed beds to treat trace quantities of icropollutants. Many years of research and industrial use has ensured that it is highly effective as a water treatment process. However, GAC is expensive and economic considerations mean it has to be recovered and re-used Powdered Activated Carbon (PAC; is a cheaper alternative but the particle size range means it is unsuitable for packed bed applications. This thesis describes a novel method for utilising PAC to treat micropollutants. By contacting carbon paracles with air bubbles, under conditions o.lrotational shear and a binding agent, oleyl alcohol, carbon-coated air bubbles form which remain stable while agitated byflowing water. A stabilised air bubble can be visualised as a phere with an impervious core (the air bubble), surrounded by a thin layer of porous matehal (PAC). Theory dictates that all these stabilised air bubbles can be moved counter-currently to a contaminated stream, higher throughputs than conventional packed beds are possible. Several aspects of this process are investigated. Bubble generation is critical and so the literature was reviewed to explain the mechanisms involved Practical use was made of this knowledge in designing a larger bubble generator. Transferring the coated-bubbles to a contacting column was difficult. Problems associated with the various methods employed are described and recommendations are made for improvement. The contacting column was used to assess the stability and adsorptive capacity of the bubbles. The possibility of counter-current flow using stabilised air bubbles was also evaluated and found to be incompatible with the current column design. The stabilised bubbles collected in the column resembled an inverted fluidised bed. Experiments were performed to test Richardson and Zaki's hydrodynamic laws for conventional fluidised beds were applicable to inverted beds. The adsorptive capacity of the bubbles was assessed by dosing the water with trace levels of phenol and p-chlorophenol. Samples taken from before and after the fluidised bed were analysed and compared. The results were inconclusive, although the concentration profile produced indicated that flow through the bubble bed was piston-flow.

Previous research has demonstrated that pool-riffle bedforms play a critical role in channel stability and ecosystem health in many natural gravel-bed channels. Although the bedform length is known to scale with channel width, no experimental research has yet isolated the effect of bedform length on pool-riffle hydrodynamics. To improve the understanding of the hydrodynamics of these bedforms so that they can be better incorporated in restoration practices, flume experiments were conducted testing the flow at seven different bedform lengths. Velocity profiles are measured in a 17 m flume with movable PVC bedforms using ultrasonic velocity profilers (UVPs). Smooth two-dimensional (no sinuosity) bedforms are used in order to isolate the key dynamics in convective acceleration and deceleration. The angle of transition between pool and riffle heights was 7°, so that permanent flow separation did not occur. Parameters calculated from the velocity and turbulence profiles include the Coles’ wake parameter (a measure of the deviation from the log law), shear stress estimated from the velocity profile, shear stress estimated from the Reynolds shear stress, and vertical velocity. From the individual velocity time series, the integral length scale and the integral time scales are also calculated. Overall, the length of riffles and pools exert a fundamental control on the distribution of flow and turbulence within a channel. In the pool, energy is dissipated both through turbulence and as the flow is redistributed to uniform flow conditions. In the riffle, kinetic energy increases as the flow velocity increases, and as the length increases, the flow moves towards a new uniform flow condition. The results start to explain the reasons behind the persistent scaling relation between width and bedform length. It can be concluded that uniform flow conditions exist at the end of the pool when the bedform length ratio is greater than approximately 1:5.0 when the riffle length is held constant, and that uniform flow conditions are no longer observed at the end of the pool when the bedform length ratio exceeds 1:7.0 when the pool length is held constant. Future research should concentrate on extending the results to include three-dimensional pool-riffle configurations, repeating bedform configurations, internal scaling parameters, and sediment transport. Ultimately, as the hydrodynamics of pool-riffle sequences are better understood, better bedform designs can be implemented in restoration projects.

The jaw musculature of Champsosaurus has been enigmatic since the taxon was first described. The extant phylogenetic bracketing method is used to determine the morphology of the jaw adductor musculature. Rotational mathematics is used to calculate the muscle forces, torques, angular accelerations, and angular velocities generated by the jaw muscles. The mechanical strength of the skulls of neochoristoderes and crocodilians are investigated using finite element analysis. Finally, the hydrodynamic performance of the skulls of neochoristoderes and crocodilians is studied. The analysis is used to compare neochoristoderes to their extant ecological analogues, crocodilians, and determine the palaeoecological implications of the results. It was found that Champsosaurus rotates the lower jaw faster, the mechanical strength was lower, and shows better hydrodynamic performance than crocodilians. The results suggest that Champsosaurus was ideally suited to prey upon small or juvenile fish, and did not overlap its niche with sympatric crocodilians. / Systematics and Evolution

A theoretical non-hydrostatic model is developed to describe the dynamics of a two-layer shallow water system in the presence of viscous and Coriolis effects. The Navier-Stokes equations are integrated over the water depth in each layer to obtain the layer-mean equations. To close the resulting equation set, perturbation expansions of the vertical momentum equation are used and the dynamic pressures are solved in terms of wave elevations and horizontal velocities. A preliminary analysis is also carried out and a result for the quasigeostrophic problems is given based on an previous study. Our final model is of the Bousinesq class which is nonlinear and dispersive, and includes the effects of surface wind stress, bottom friction, eddy diffusion and earth rotation. It is shown that our new model can be readily reduced to previous inviscid non-hydrostatic models. Our model can be used in numerical simulations to study real ocean problems such as hurricane generated waves, tidal induced current, and interactions among surface waves, internal waves and variable topographies. / Thesis (M. S.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 55-59). / UHM: Has both book and microform. / U.S. Geological Survey; project no. 06; grant agreement no. 14-08-0001-G2015

Three interrelated topics in ship hydrodynamics - resistance, wave-making and wave decay - are investigated in an attempt to improve the accuracy of some simple methods used in the preliminary design of thin ships. Several published sets of data from classical and recent boundary layer experiments on flat plates are used to estimate boundary layer quantities such as thicknesses and eddy viscosities. These quantities are subsequently used to modify the hull shape and the free-surface boundary condition as a means of including viscous effects on wave-making and ship-wave decay. A recent technique is used to analyse 161 experimental flat-plate turbulent boundary layer velocity profiles, and a new skin-friction line is derived. Some practical methods are proposed for the numerical quadrature of integrals arising in thin-ship hydrodynamics. We demonstrate that for some integrals, rapid oscillation, rather than being a hindrance to accurate quadrature, can actually be beneficial if appropriate techniques are employed. We find that boundary layer displacement thickness effects on wave resistance are very small and can be safely ignored for full-size vessels. On the other hand, the idea of a detachment layer, an indication of where the boundary layer begins to thicken rapidly, is shown to have a significant effect on wave resistance. A modification to the Kelvin free-surface boundary condition is used as a means of including viscous effects on wave-making. Detailed comparisons of total resistance predictions and experiments are made for three model-size Wigley hulls. It is shown that inclusion of viscous effects smooths out the well-known humps and hollows in the wave resistance curves calculated using Michell's (inviscid) integral. Predictions of the total resistance of a model Wigley hull using Michell's integral and a simple skin-friction line are shown to be as good as those of a modern CFD computer code. Furthermore, the simple method does so in a very small time on an inexpensive computer. The effect of employing a form factor on the skin-friction is shown to improve correlations between resistance predictions and experiments. It has recently been proposed that a form factor should also be applied to the wave resistance. We show that good predictions are indeed possible, but that the use of a modified form of Michell's integral and an “appropriate" value of the eddy viscosity leads to even better agreement. Two existing wave-decay models are examined and a new formulation is suggested that combines the theoretical – 1/2 decay rate of transverse waves with the -1/3 decay rate of diverging waves. The effects of viscosity on ship-wave decay are considered. It is found that large values of the viscosity, of the order required to have a significant effect on wave resistance, lead to an over-damping of far-field waves at low Froude numbers. We show that it may be possible to get a rough estimate of the (ambient) eddy viscosity from an analysis of the decay of ship-waves with transverse distance from the sailing line, without resorting to computationally expensive Fourier transform methods. Three wave decay models are used to estimate the eddy viscosity from the behaviour of the wave decay. The model that uses the theoretical decay rates of transverse and of diverging waves is found to be slightly better at recapturing the original eddy viscosity than the other two models. / Thesis (Ph.D.) - University of Adelaide, School of Mathematical Sciences, 2009

Thesis (PhDApSc(MineralsandMaterials))--University of South Australia, 2007.

Thesis (PhD) -- University of South Australia, 1994

The relationship between operating parameters, cell hydrodynamics, flotation response and scale-up of flotation rates has been explored using three geometrically similar Rushton turbine flotation cells with volumes of 2.25, 10 and 50dm³. Mean energy dissipation values measured using Laser Doppler Velocimetry (LDV) and a torque turntable method were in good agreement. As the cell volume was increased, the mean energy dissipation was proportional to N³D, rather than N³D² as may be expected based on dimensional analysis. Possible reasons for this difference are discussed. Aeration resulted in a slight increase in mean energy dissipation. Bubble diameters were measured using a University of Cape Town bubble size analyser to determine the frother concentration at which a constant bubble diameter was achieved for all operating conditions and cell volumes. The critical frother concentration required to achieve this was 20 ppm MIBC.

In the design of all marine craft the prediction of a vessel??s resistance characteristics is a major consideration. The accurate prediction of resistance is particularly important in the design of modern high-speed vessels where the primary contractual obligation placed upon the builder is the vessel??s achievable speed. Investigation was made of the methods of Doctors and Day, whereby the traditional Michell wave-resistance theory, published in 1898, is improved on through a better understanding of the hydrodynamics of transom sterns and the application of statistically determined form factors. One of the difficulties with the Michell theory is how to account for the hollow that forms behind a transom stern, a feature prevalent in high-speed vessels. A common approach in the numerical prediction of wave resistance for transom-stern vessels is to discretize the hollow as a geometrically-smooth addition to the vessel. Therefore, of great importance in accurate prediction of wave resistance is the hydrodynamics of, and in particular, the length and depth of the hollow formed behind the transom stern. Accordingly, a systematic series of transom-stern models were tank tested at various drafts and speeds in order to determine experimentally the length and depth of the hollow as a function of vessel speed, draft and beam. From the experimental data, algorithms for the determination of the length and depth of the transom hollow, have been developed and utilised in the discretization of the transom hollow for prediction of resistance using the Michell wave- resistance theory. Application of the developed hollow algorithms produced significant improvements in correlation of the experimental and theoretical predictions of total resistance, particularly in the lower Froude range. In addition to the transom-hollow investigation, form factors were obtained using least-squares regression of existing experimental data. The form factors were based on the major geometric parameters of the models used. In the research presented here, the method was applied to a large range of published resistance data for high-speed displacement vessels. Considerable improvement in correlation, between theoretical and experimental predictions of total resistance, was obtained by incorporating the calculated form-factors into the total resistance formulation.