Thesis (Ph.D.)--University of Adelaide, Dept. of Applied Mathematics, 1998? / Errata pasted onto front end paper. Bibliography: leaves 131-136.

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Kuo-Chuin Wong, College of Marine and Earth Studies. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [195]-201).

Tidal stream energy presents challenges that will require the development of new engineering tools if designs are to harness this energy source effectively. At first glance one might imagine that tidal stream energy can be treated as wind with appropriate adjustment for fluid properties of water over air, and account taken of the harsher offshore environment; both waves and turbulence. However, it is now well accepted that the flow past turbines that are constrained by the local sea bed, sea surface, and possibly also neighbouring turbines and channel sides, will differ markedly from that of an ostensibly unblocked wind turbine. Garrett & Cummins (2007) were the first to demonstrate that operating a turbine in a non- negligibly blocked flow passage presents a different flow solution and importantly a significant opportunity to enhance the power that can be delivered by blocked turbines with the limit of power extraction exceeding the Lanchester-Betz limit for operation of unblocked wind turbines. Although it is impractical to array real turbines across the entire width of a channel it has been proposed to use short arrays of turbines making use of local constructive interference (blockage) effects; Nishino & Willden (2012) showed that although the phenomenal power limits of Garrett & Cummins are unobtainable in a real flow, a significant uplift in the limit of power extraction can be achieved for short fences of turbines arrayed normally to the flow in wide cross-section channels. However, it does not follow that rotors designed using unblocked wind turbine tools are capable of extracting any more power than they are designed for and hence the power uplift made available through blockage effects may be squandered. This thesis sets out to develop design tools to assist in the design of rotors in blocked environments that are designed to make use of the flow confinement effects and yield rotors capable of extracting some of the additional power on offer in blocked flow conditions. It is the pressure recovery condition used in wind turbine design that requires relaxation in blocked flow conditions and hence it is necessary to resort to a computational framework in which the free stream pressure drop can be properly accounted for. The tool of choice is a computational fluid dynamics embedded blade element method. As with all models with semi-empirical content it is necessary to select and test correction models that account for various simplifications inherent to the use of the blade element method over a fully blade resolved simulation. The thesis presents a rigorous comparison of the computational model with experimental data with the various correction methods employed. The tool is then used to design rotors, first for unblocked operation, with favourable comparison drawn to lifting line derived optimal Betz rotor solutions. The final objective of the study is to design rotors for operation in short fence configurations of four turbines arrayed normally to the flow. This is accomplished and it is shown that by using bespoke in situ rotor design it is possible to extract more power than possible with non-blockage designs. For the defined array layout and operating conditions, the bespoke rotor array design yields a power coefficient 26% greater than the implied Betz limit for an unblocked rotor and 4% greater than operating a rotor designed in isolation in the same array.

No description available.

In spite of the widely perceived importance of suspended particulate material (SPM) , its distribution in the shelf seas and the processes controlling its variation are little known. This thesis reports an exploratory study of the spatial and time dependant variability of SPM in an area of the northern Irish Sea. SPM was determined both directly by gravimetric methods and via measurements of beam attenuation (c). Spatial distributions were determined from grid surveys using a profiling transmissometer. In addition a six month record of beam attenuation and current velocity was obtained from a site off the north coast of Anglesey. A clear spatial pattern in the surface distribution of c was observed which was similar to the distribution of h/ta, suggesting that concentrations of SPM are determined by the availability of TKE from tidal stirring. A strong seasonal cycle of c was observed in mixed water, with values decreasing in June, July and August which suggested a reduction in the supply of SPM during summer. In stratified water, high concentrations of SPM remained confined to the dense layer below the thermocline. The seasonal cycle was observed in the time series from the mooring, but in addition there was a marked response to tidal currents in the spring and in autumn. Close analysis of the record in April and May-showed signals at M% and M4frequencies. These variations in c were attributed to a local response to tidal currents causing erosion of the sea-bed and to the oscillation of a horizontal gradient in c in the region. A regression model was found to explain 35% of the variance in data from a5 week time series. 70% of the variance was explained for four day time series, near spring tides. The relationship between c and tidal flows was more marked at spring tides than at neaps.

THE THESIS This thesis describes the investigation of an estuarine front, the 'tidal-intrusion front, which was initially found in the Seiont estuary, North Wales but has subsequently been observed at other locations. In the Seiont, the front forms after low water, moves a considerable distance into the estuary to an upstream limit, retreats from the estuary and finally weakens, all within the duration of the flooding tide. It separates mixed from stratified regimes and is characterised by its surface appearance; inside the estuary, the front is 'V'-shaped with its apex directed towards the estuary head. Associated convergent flows include collection of all surface buoyant material at the apex of the V. Following a considerable field investigation of the front in the Seiont, two short periods were spent studying a similar feature in Loch Creran, Scotland. In the process of investigating other sites to determine the range of estuarine parameters appropriate to a stable tidal-intrusion front, an alternative estuarine convergence was discovered in the Conwy estuary, North Wales. The Conwy shows similar frontal behaviour to the Seiont during the early part of the flood tidal phase, but increased flood currents subsequently break down stratification producing an estuary of the 'well-mixed' class. 5 Throughout the remainder of the flood tide an axial line of debris forms along a substantial proportion of the estuary length. The persistence of the line indicates a secondary circulation which includes surface convergence towards the estuary axis. However, the line disperses at high water and no similar system is apparent during the ebb. The specific aims of the thesis may be summarised with respect to: a) the tidal-intrusion or T.I. front; i) to understand the parameters which govern the movements of the front. ii) to explain and/or reproduce by modelling, the three-dimensional aspects of the 'V'-shaped frontal boundary. b) the axial convergence or A.C. i) to detrmine the nature of the secondary circulation in the Conwy i.e. the pattern of cross-sectional secondary velocities. ii) to determine a mechanism which accounts for both the production of a sustained secondary circulation and its existence only during the flood phase of the tide. and finally, we attempt to define the stable parameter ranges for both types of convergence.

A review of the technology of useful conversion of wave power and tidal power is presented. These two power resources are reviewed separately, but on the same basis: principles of operation, existing devices or plants and research and development. Promising wave power devices in Britain, the United States and Europe are discussed. If wave power is to be competitive, one of the first requirements may be energy densification. Proposed energy densification schemes include resonance, high pressure water and wave focussing. Wave focussing is a Norwegian invention, technically feasible, and although more research and development is required, it appears to be more promising than alternative forms of wave power utilisation. According to a preliminary cost analysis, it could be competitive with conventional hydro-electric power. The large scale exploitation of tidal power has been considered seriously for about half a century; the literature on the topic is voluminous. The main limitations of tidal power are its intermittent nature and the high costs involved in the construction of a plant. The existing pilot plants at the Rance and Kislaya Guba have respectively proved that tidal power is technically feasible and that construction costs could be reduced. With the rapid increase in the price of fossil fuels, tidal power plants may be realised at the two best sites in the world, the Bay of Fundy and the Severn Estuary.

No description available.

Hydrokinetic tidal power is a novel and emergent technology undergoing continuous advancement with much of the progress focused on large utility scale projects. This resource is potentially underutilized because much of the coastal United States, despite having substantial tidal currents, do not have the deep and wide environments required by most of the developing turbine technology. This dissertation includes a detailed characterization of the tidal hydrodynamics for Rose Dhu Island, Georgia used for a tidal energy resource assessment as well as a general feasibility study for tidal estuaries with extensive wetlands. For predictions and evaluation of the estuarine hydrodynamics, data from an existing numerical model of the estuary encompassing the island is utilized. Field measurements in close proximity to the island are used to calibrate the model as well as characterize local hydrodynamic features. After the model calibration, the simulation data is used to evaluate the hydrodynamics. Wetland dominated estuaries commonly have a high degree of non-linear distortion which govern the relative durations and strengths of the tidal stages and thus the overall hydrodynamics and incoming hydrokinetic energy. The Ogeechee Estuary is characterized as ebb dominant with peak ebb and flood volume fluxes near high tide as a result of the increased storage capacity of the wetlands. Lowering the average wetland elevation in the model decreased ebb dominance and quickened the transition from flood to ebb tide. Increased domain friction in the model removed energy from the system and reduced ebb dominance. Enhanced model marsh friction reduced lateral flooding of the wetlands as well as ebb dominance. Localized measurements surrounding the island are analyzed to determine a location near the southwest coast of the island as a hydrokinetic energy hotspot. A kinematic and dynamic analysis is performed using channel transect measurements to identify key physical processes behind the hotspot formation. The hotspot forms due to sub-critical flow acceleration over a singular bump in the topography. High streamwise momentum is further concentrated at the hotspot due to secondary circulation cells across the channel. Flood tide circulation is characterized by two co-rotating cells induced by channel curvature and delineated by the bump. Ebb circulation consists of two counter-rotating cells from flow confluence of two upstream channels. Once the hydrodynamics are understood, the theoretical and technical resource assessment of the island is completed. A sensitivity analysis of hydrokinetic energy and tidal distortion is performed on synthetic data. For a principle constituent and its first harmonic, distortion greatly changes as does the distribution of velocities and energy as the relative phase varies. While the theoretical energy remains consistent, the technical energy can greatly vary. This effect is reduced with the addition semi-lunar variation. Using a simplified analytical method, the maximum average channel power is estimated as 8.80 MW. For the hotspot it is estimated that there is 30.3 MWh available to capture yearly with an average power of 3.46 kW for a turbine with an area of 10 square meters. For the same turbine area with conservative efficiencies, the hotspot could provide a yearly technical energy of 10.9 MWh with an average power of 1.25kW for the island. Due to the complex localized hydrodynamics, both the theoretical and technical resource varies greatly across and along the channel. These considerations are more pertinent when performing a hydrokinetic energy resource assessment in a marsh estuary than for large scale bay-ocean exchange environments, the present industry focus.