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Currently, the accurate prediction of the impact of an extreme wave on infrastructure located near shore is difficult to assess. There is a lack of established methods to accurately quantify these impacts. Extreme waves, such as tsunamis generate, through breaking, extremely powerful hydraulic bores that impact and significantly damage coastal structures and buildings located close to the shoreline. The damage induced by such hydraulic bores is often due to structural failure. Examples of devastating coastal disasters are the 2004 Indian Ocean Tsunami, 2005 Hurricane Katrina and most recently, the 2011 Tohoku Japan Tsunami. As a result, more advanced research is needed to estimate the magnitude of forces exerted on structures by such bores. This research presents results of a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method which is used to simulate the impact of extreme hydrodynamic forces on shore protection walls. Typically, fluids are modeled numerically based on a Lagrangian approach, an Eulerian approach or a combination of the two. Many of the common problems that arise from using more traditional techniques can be avoided through the use of SPH-based models. Such challenges include the model computational efficiency in terms of complexity of implementation. The SPH method allows water particles to be individually modeled, each with their own characteristics, which then accurately depicts the behavior and properties of the flow field. An open source code, known as SPHysics, was used to run the simulations presented in this thesis. Several cases analysed consist of hydraulic bores impacting a flat vertical wall as well as a sloping seawall. The analysis includes comparisons of the numerical results with published experimental data. The model is shown to accurately reproduce the formation of solitary waves as well as their propagation and breaking. The impacting bore profiles as well as the resulting pressures are also efficiently simulated using the model.

We study the hydrodynamics of wedge,knuckle and box cross-sectional profiles undergoing transient extreme motions, in particular forced entry and exit at constant velocity or acceleration. Extensive data for the forces, pressures and free-surface profiles is generated by an extension of a fully-nonlinear boundary-integral method. The code is thoroughly checked by altering the time step and particle spacing on the bodies and Lagrangian free-surface markers, and, for the wedge,checking self-similarity for the infinite Froude number (gravity free) constant velocity entry. Difficulties with inviscid flow around sharp corners are discussed. Results for exit are of particular interest since no zero-gravity approximation is valid and this precludes application of existing slamming theories in reverse. Whilst entry generally gives larger free-surface motions (spray jets), pressures and hence forces, calculation of exit is needed for the velocity of subsequent slamming and so is of practical interest too. These results are compared with an approximate analytical model, based on Schwarz-Christoffel transformations to calculate the infinite-frequency added mass of the cross-section below the mean water line. For constant acceleration of both entry and exit, the analytical theory is good during the early stages of motion. Later, the assumption of an undisturbed mean water level is clearly violated; the exact calculations show a large amount of draw-down (up-rise), the free-surface making contact with the body well below (above) the mean water level. We therefore examine the effect of reducing (increasing) the submerged body volume to take account of this, which prolongs the agreement between the results considerably and therefore might be used to improve practical calculation of extreme ship motions using existing strip theory codes. Full sets of numerical data input/output are provided in the appendices, together with some mathematical details. We also speculate on the possible application of John's equation to wedge entry.

Supercavitating torpedoes pose new threats to submarines, surface ships, and shore targets whose current countermeasures are inadequate against this technology. These torpedoes have the advantage over their predecessors and companion weapons of dramatically increased speed, which reduces the reaction time available for deploying a countermeasure heightening the threat to their intended target. Proliferation of supercavitating torpedoes has motivated research on countermeasures against them as well as on the fluid phenomenon which makes them possible. The goal of this research was to investigate an envisaged countermeasure; an acoustic field capable of slowing or diverting the weapon by disrupting the cavitation envelope. The research focused on the interactions between high-level sound signals and a supercavity produced by a small free-flying projectile. In order to conduct this study it was necessary to achieve three preliminary accomplishments involving the design of: 1) experimental apparatus that allowed for the study of a small-scale supercavitating projectile in the laboratory environment; 2) apparatus and software for measuring and recording information about projectile dynamics and supercavity geometry; and 3) an acoustic array and power source capable of focusing the desired sound signal in the path of the supercavitating object. Positive results have been found which show that the accuracy of a supercavitating projectile can indeed be adversely affected by the sound signal. This research concludes with results that indicate that it is acoustic cavitation in the medium surrounding the supercavity that is responsible for the reduced accuracy. A hypothesis has been presented addressing the means by which the acoustic cavitation could cause this effect. Additionally, corrugations on the cavity/water interface imposed by the pressure signal have been observed and characterized.

Slot-rectangular spouted beds, with rectangular cross-section and slotted gas inlets, have been proposed as a solution to overcoming scale-up difficulties with conventional axisymmetric spouted beds. They can be utilized in gas/particle processes such as drying of coarse particles and coating of tablets. However, application of this spouted bed was limited because of instability and insufficient hydrodynamic studies. The present work is therefore aimed at the study of hydrodynamics, stability and scale-up of slot-rectangular spouted beds. The hydrodynamic study was carried out in four slot-rectangular columns of various width-to-thickness ratios combined with various slot configurations, particles of different properties and a range of operating conditions. Hydrodynamics of slot-rectangular spouted beds showed major similarity with conventional spouted beds. However, equations and mechanistic models adopted from conventional axisymmetric spouted beds generally failed to provide good predictions for the three-dimensional slot-rectangular geometry. New empirical correlations were derived for the minimum spouting velocity and maximum pressure drop for different slot configurations. Slot-rectangular spouted beds also showed more flow regimes than conventional spouted beds. Nine flow regimes, as well as unstable conditions, were identified based on frequency and statistical analysis of pressure fluctuations. Slot geometrical configuration was found to be the main factor affecting the stability of slot-rectangular spouted beds. A comprehensive hydrodynamic study on the effect of slot configuration was therefore carried out. Slots of smaller length-to-width ratio, smaller length and greater depth were found to provide greater stability. Stable criteria for the slot configuration were found consistent with the conventional axisymmetric spouted beds with extra limitation on slot length-to-width ratio and slot depth. Local distributions of pressure, particle velocity and voidage, as well as spout shape and particle circulating flux, were compared for different slot configurations. Higher slot length-to-width ratios lead to slightly higher particle circulation rates. A previously proposed scale-up method involving multiple chambers was tested in the present work using multiple slots. Instability caused by the merging of multiple spouts and asymmetric flow was successfully prevented by suspending vertical partitions between the fountains. Some criteria and guidelines were also proposed for scale-up using multiple chambers.

A weakly nonlinear stability analysis was conducted for the flow induced in an incompressible, Newtonian, viscous fluid lying between two infinite parallel plates which form a channel. The plates are oscillating synchronously in simple harmonic motion. The disturbed velocity of the flow was written in the form of a series in powers of a parameter which is a measure of the distance away from the linear theory neutral conditions. The individual terms of this series were decomposed using Floquet theory and Fourier series in time. The equations at second order and third order in were derived, and solutions for the Fourier coefficients were found using pseudospectral methods for the spatial variables. Various alternative methods of computation were applied to check the validity of the results obtained. The Landau equation for the amplitude of the disturbance was obtained, and the existence of equilibrium amplitude solutions inferred. The values of the coefficients in the Landau equation were calculated for the nondimensional channel half-widths h for the cases h = 5, 8, 10, 12, 14 and 16. It was found that equilibrium amplitude solutions exist for points in wavenumber Reynolds number space above the smooth portion of the previously determined linear stability neutral curve in all the cases examined. Similarly, Landau coefficients were calculated on a special feature of the neutral curve (called a ???finger???) for the case h = 12. Equilibrium amplitude solutions were found to exist at points inside the finger, and in a particular region outside near the top of the finger. Traces of the x-components of the disturbance velocities have been presented for a range of positions across the channel, together with the size of the equilibrium amplitude at these positions. As well, traces of the x-component of the velocity of the disturbed flow and traces of the velocity of the basic flow have been given for comparison at a particular position in the channel.

The current work has developed a CFD model to characterise a pseudo-annular photocatalytic bubble column reactor. The model development was divided into three stages. Firstly, hydrodynamic assessment of the multiphase fluid flow in the vessel, which incorporated residence time distribution analysis both numerically and experimentally for validation purposes. Secondly, the radiation distribution of the UV source was completed. The final stage incorporated the kinetics for the degradation the model pollutant, sodium oxalate. The hydrodynamics were modelled using an Eulerian-Eulerian approach to the multiphase system with the standard k- turbulence model. This research established that there was significant deviation in the fluid behaviour in the pseudo-annular reactor when compared with traditional cylindrical columns due to the nature of the internal structure. The residence time distribution study showed almost completely mixed flow in the liquid phase, whereas the gas phase more closely represented plug flow behaviour. Whilst there was significant dependence on the superficial gas flow rate the mixing behaviour demonstrated negligible dependence on the liquid superficial velocity or the liquid flow direction, either co- or counter- current with respect to the gas phase. The light distribution was modelled using a conservative variant of the Discrete Ordinate method. The model examined the contribution to the incident radiation within the reactor of both the gas bubbles and titanium dioxide particles. This work has established the importance of the gas phase in evaluating the light distribution and showed that it should be included when examining the light distribution in a gas-liquid-solid three-phase system. An optimal catalyst loading for the vessel was established to be 1g/L. Integration of the kinetics of sodium oxalate degradation was the final step is developing the complete CFD model. Species transport equations were employed to describe the distribution of pollutant concentration within the vessel. Using a response surface methodology it was shown that the reaction rate exhibited a greater dependency on the lamp power that the lamp length, however, the converse was true with the quantum efficiency. This work highlights the complexity of completely modelling a photocatalytic system and has demonstrated the applicability of CFD for this purpose.

Bibliography: leaves 169-178 / iv, 201 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1989

Whole document restricted until 2010, see Access Instructions file below for details of how to access the print copy. / Blind Mexican cave fish (Astyanax fasciatus) lack a functioning visual system, and are known to use self-generated water motion to sense their surroundings; an ability termed hydrodynamic imaging. Nearby objects distort the flow field created by the motion of the fish. These flow distortions are sensed by the mechanosensory lateral line. Little is known about the fluid mechanics involved in hydrodynamic imaging, or how the behaviour of the fish might influence their ability to sense the world around them. Automated image analysis was used to study the effects of swimming kinematics on the ability of the fish to sense their surroundings when introduced into a novel environment. The fish reacted to avoid head-on collisions with a wall at a remarkably short mean distance of 4.0 ± 0.2 mm. The ability of the fish to react, was dependent on whether they were beating their tail as they approached the wall. When following surfaces, such as a wall, the fish changed their swimming kinematics significantly and used both tactile and hydrodynamic information. Measuring the tendency of the fish to follow a tightening curve showed the fish to be moderately thigmotactic. The flow fields around freely swimming fish were experimentally measured using Particle Image Velocimetry (PIV). A new algorithm was developed to calculate the pressure field around the fish based on the velocity field measured using PIV. The algorithm was validated against analytical and computational fluid dynamic (CFD) solutions. The flow fields around gliding fish and the stimuli to the lateral line of the fish were calculated using CFD models, validated against the experimental PIV data. The flow fields changed in characteristic ways as the fish approached a wall head-on or swam parallel to a wall. At 0.10 body lengths from a wall, the stimulus to the lateral line was estimated to be sufficient for the fish to be able to detect the wall, but this decreased rapidly with increasing distance from the wall. The CFD models suggested that the velocity of the fish does not affect the distance at which they detect an object. Hydrodynamic imaging is a short range sensory ability and blind cave fish require their sensitive lateral line and fast reactions in order to be able to use it to sense the world around them and avoid collisions. The information gained about the fluid mechanics of hydrodynamic imaging, and the flow measurement and modelling techniques developed here will be useful for further study of this remarkable ability.

Whole document restricted until 2010, see Access Instructions file below for details of how to access the print copy. / Blind Mexican cave fish (Astyanax fasciatus) lack a functioning visual system, and are known to use self-generated water motion to sense their surroundings; an ability termed hydrodynamic imaging. Nearby objects distort the flow field created by the motion of the fish. These flow distortions are sensed by the mechanosensory lateral line. Little is known about the fluid mechanics involved in hydrodynamic imaging, or how the behaviour of the fish might influence their ability to sense the world around them. Automated image analysis was used to study the effects of swimming kinematics on the ability of the fish to sense their surroundings when introduced into a novel environment. The fish reacted to avoid head-on collisions with a wall at a remarkably short mean distance of 4.0 ± 0.2 mm. The ability of the fish to react, was dependent on whether they were beating their tail as they approached the wall. When following surfaces, such as a wall, the fish changed their swimming kinematics significantly and used both tactile and hydrodynamic information. Measuring the tendency of the fish to follow a tightening curve showed the fish to be moderately thigmotactic. The flow fields around freely swimming fish were experimentally measured using Particle Image Velocimetry (PIV). A new algorithm was developed to calculate the pressure field around the fish based on the velocity field measured using PIV. The algorithm was validated against analytical and computational fluid dynamic (CFD) solutions. The flow fields around gliding fish and the stimuli to the lateral line of the fish were calculated using CFD models, validated against the experimental PIV data. The flow fields changed in characteristic ways as the fish approached a wall head-on or swam parallel to a wall. At 0.10 body lengths from a wall, the stimulus to the lateral line was estimated to be sufficient for the fish to be able to detect the wall, but this decreased rapidly with increasing distance from the wall. The CFD models suggested that the velocity of the fish does not affect the distance at which they detect an object. Hydrodynamic imaging is a short range sensory ability and blind cave fish require their sensitive lateral line and fast reactions in order to be able to use it to sense the world around them and avoid collisions. The information gained about the fluid mechanics of hydrodynamic imaging, and the flow measurement and modelling techniques developed here will be useful for further study of this remarkable ability.