The prediction of coastal groundwater movement is necessary in coastal management. However, the study in this field is still a great challenge due to the involvement of tidal-groundwater interactions and the phenomena of hydrodynamic dispersion between salt-fresh water in the coastal region. To date, numerous theories for groundwater dynamic have been made available in analytical, numerical and also experimental forms. Nevertheless, most of them are based on the zeroth-order shallow flow, i.e. Boussinesq approximation. Two main components for coastal unconfined aquifer have been completed in this Thesis: the vertical beach model and the sloping beach model. Both solutions are solved in closed-form up to higher order with shallow water parameter ([epsilon]) and tidal amplitude parameter ([alpha]). The vertical beach solution contributes to the higher-order tidal fluctuations while the sloping beach model overcomes the shortcomings in the existing solutions. From this study, higher-order components are found to be significant especially for larger value of [alpha] and [epsilon]. Other parameters such as hydraulic conductivity (K) and the thickness of aquifer (D) also affect the water table fluctuations. The new sloping solution demonstrated the significant influence of beach slope ([beta]) on the water table fluctuations. A comprehensive comparison between previous solution and the present sloping solution have been performed mathematically and numerically and the present solution has been demonstrated to provide a better prediction

Current hydro-turbines aim to capture the immense energy available in tidal movements, however commonly applied technologies rely on principles more applicable in hydroelectric dams. Tidal stream currents, such as in Coastal Georgia, are not strong enough to make such turbines both efficient and economically viable. This research proposes a novel low-energy vortex shedding vertical axis turbine (VOSTURB) to combat the inefficiencies and challenges of hydro-turbines in low velocity free tidal streams. Some of the energy in tidal streams is extracted naturally from vortex shedding; as water streams past a bluff body, such as pier, low pressure vortices form alternatively on each side, inducing a rhythm of pressure differentials on the bluff body and anything in its wake. VOSTURB aims to capture this energy of the vortices by installing a hydrofoil subsequent to the bluff body. This foil, free to oscillate, translates the vortex energy into oscillatory motion, which can be converted into a form of potential energy. The presented research will act as a 'proof of concept.' It aims to assess such foil motion, or the ability of VOSTURB to capture vortex energy, and begin to assess the amount of tidal energy that can be theoretically harnessed. In this study a small scale model of VOSTURB, a cylindrical bluff body with a hammer shaped hydrofoil, was tested in a hydraulic flume for various mean flow speeds. Tangential accelerations of the foil's center of gravity were obtained through the use of an accelerometer. The acceleration data was analyzed utilizing Fourier analysis to determine the fundamental frequency of the wing oscillations. The available power to be harnessed from the oscillatory motion was then estimated utilizing this fundamental frequency. Ultimately it was found that the frequency of the VOSTURB foil oscillations corresponded highly with the theoretical frequency of vortex shedding for all moderate to high flow speeds. Low speeds were found to produce inconsistent and intermittent small oscillations. This signifies at moderate to high flow speeds, VOSTURB was able to transform some vortical energy into kinetic. The maximum average power obtained 8.4 mW corresponded to the highest flow velocity 0.27 m/s. Scaled to Rose Dhu prototype conditions this represented 50 W at a flow velocity of 0.95m/s, the maximum available at Rose Dhu. Although it was ascertained that VOSTURB could consistently capture some of the vortical energy; the percentage of which could not be calculated with certainty. Thus, the average kinetic power assessments of the foil were compared to the available power of the mean flow for each flow speed calculated by two methods: (1) over the foil's swept area; (2) the area of fluid displaced by the bluff body immediately in front of the foil. The maximum efficiency of the foil, found for the fastest flow speed was at 18% and 45% respectively. It was found that both average foil power, available flow power, and efficiency all decreased with a decrease in flow velocity. This study can serve as only a preliminary study for the effectiveness of VOSTURB as a hydro-turbine for tidal power. In the experiments, the foil was allowed to oscillate freely with little resistance. Future testing of VOSTURB needs to observe whether the vortex energy can overcome the resistive torque introduced by a generator to induce oscillatory motion as well as further optimize the foil design. While the testing in this project assesses the kinetic energy or power of the vortex shedding, this future testing will provide insight into the actual work that can actually be converted into potential energy or power. Complementing this research, both a Harmonic Analysis of Least Squares (HAMELS) and a Complex Empirical Orthogonal Function (CEOF) Analysis was conducted on available surface height and current velocity data separately from an available Regional Ocean Modeling System (ROMS) model of Coastal Georgia. Such analysis were conducted to observe spatial and temporal tidal patterns advantageous to a possible prototype installation of a tidal turbine such as VOSTURB. The more conventional HAMELS analysis, which isolates components of a signal with a certain frequency, identified temporal and spatial patterns attributed to tidal constituents. CEOF analysis, where major patterns of variance are identified not according to prescribed frequencies, was employed to identify any patterns possible not attributed to the tidal constituents. This study was also in part to observe whether the CEOF analysis could identify any patterns of tidal propagation that could not be resolved by the HAMELS analysis. The CEOF and HAMELS analysis of the surface height output produced very similar results: major modes of surface height variation due to the diurnal and semidiurnal tidal constituents propagating up the estuary. The CEOF results did not produce any additional information that could not be found through the HAMELS analysis of the constituents and presented such results in an arguably more convoluted manner. In addition, the surface height analysis provided no direct insight into areas more advantageous to tidal power. The CEOF analysis of the vector current velocity data however did provide some insight. The CEOF of the current data was able to isolate patterns of variance corresponding to the tidal constituents. However, the CEOF was also able to identify local 'hotspots' of high current magnitudes not resolved by HAMELS. These local areas of high current magnitudes, most likely due to changes in hydrodynamic conditions such as channel constrictions, are advantageous for tidal power applications. These general areas could serve as a starting point for the location selection process for a possible prototype installation of VOSTURB if the area was refined more. Ultimately for a prototype installation of VOSTURB, further experimentation and analysis is required for both the turbine design and placement, such as a power conversion methodology for the turbine and a more spatially resolute set of data to perform a CEOF analysis on. With these tasks completed, the prototype installation will be part of a larger effort between the Georgia Institute of Technology and the Girl Scouts of America to create completely sustainable "Eco-Village" on Rose Dhu Island, GA. With an extensive community outreach planned to educate the public, Rose Dhu, along with championing hydrokinetic energy, will serve as a paradigm for sustainable design and energy.

Because the volume of flow through an inlet is proportional to the tidal range and the area of the tidal basin, Texas tidal inlets have some of the largest tidal basins relative to their entrance area of any inlet. Matagorda Bay at Pass Cavallo has an area of about 200 square miles, but only a mean diurnal tidal range of about 1.1 feet. From tide gage records the most important events modifying tidal currents in Pass Cavallo are the numerous wind tides each year that occur most frequently during the cooler months, November through May. Wind tides are most noticeable in Matagorda Bay because the astronomical tidal range is small, the fetch long (10-20 miles) and the depth only about 12 feet. Hurricanes and river floods that would raise water levels in Matagorda Bay by even 0.5 foot occur too infrequently to affect equilibrium conditions in the inlet. Pass Cavallo has passed through three time periods since 1856: 1856-1930, 1930-1965, and post 1965. Each time period was characterized by a different, and subsequently smaller tidal discharge, cross-sectional area and tidal channel length. The tidal discharge decreased between 1929 and 1935 when the Colorado River delta cut off part of east Matagorda Bay to reduce the tidal area of Matagorda Bay, and in 1965, the Matagorda Ship Channel was dredged across Matagorda Peninsula to reduce the volume of water passing through Pass Cavallo. Other features that changed with decreasing discharge, but remained stable during each time period, were the channel pattern, and location and shape of the Gulf bar and Pelican Island. During all three periods Pass Cavallo maintained stable cross-sectional shape, and tidal flow by-passing characteristics, except during the post 1965 when neither tidal flow by-passing nor bar by-passing were dominant. Since 1856 Pass Cavallo has remained geographically stable relative to its width. The axial trough has migrated southwestward about 1000 feet during the past 100 years--or about 1/9th the distance between Matagorda Peninsula and Matagorda Island. Shorelines adjacent to the inlet also have tended to move southwestward, but at a faster rate than the axial trough. Along the western side of the pass, shoreline erosion is related to jetties interrupting sediment transport southward from the western shoreline of Matagorda Bay, and to storms eroding the constructional beach extending northward from Matagorda Island. The modern flood delta at Pass Cavallo consists of a large, sandy platform, that is lobate into Espiritu Santo Bay with salt marsh, storm-tidal flats and tidal channels. The flood delta is located to the side of the channel pattern of Pass Cavallo, and appears to be active only during the high tides of hurricanes, tropical storms and "northers". There are three informal physiographic provinces on the flood delta, each one reflecting a different sediment supply and energy regime inherent in each bay and in the Gulf. 1) The Gulf of Mexico Province has the largest and best-developed intertidal beaches, surge channels, storm-tidal flats and mounds of all three provinces. Sand is the dominant sediment. 2) Matagorda Bay Province includes large marsh islands and tidal channels with fewer large vegetated mounds. Shell is very abundant in mounds, and a storm-tidal flats contain more mud and encroaching salt marsh than in the Gulf province. 3) Espiritu Santo Bay Province is composed mostly of sandy mud or muddy sand sediment, with the exception of erosional shell beaches that face a north or south fetch of 1 to 2 miles. This is the richest area biologically, consisting mostly of salt marsh and grassflats. / text

The principle source of heterogeneity affecting flow behavior in conventional clastic reservoirs is discontinuous, low-permeability mudstone beds and laminae (shales). Simple ‘streamline’ models have been developed which relate permeability anisotropy (kv/kh ) at the reservoir scale to shale geometry, fraction, and vertical frequency. A limitation of these models, especially for tidally-influenced reservoirs, is the lack of quantitative geologic inputs. While qualitative models exist that predict shale character in tidally-influenced environments (with the largest shales being deposited near the turbidity maximum in estuaries, and in the prodelta-delta front), little quantitative shale character data is available. The purpose of this dissertation is to collect quantitative data to test hypothetical relationships between depositional environment and shale character and to use this data to make geologically-based estimates of for different reservoir elements. For this study, high-resolution, lidar point-clouds were used to measure shale length, thickness, and frequency. This dissertation reports a novel method for using distance-corrected lidar intensity returns to distinguish sandstone and mudstone lithology. Lidar spectral and spatial data, photo panels, and outcrop measurements were used to map and quantify shale character. Detailed shale characteristics were measured from four different tidally-influenced reservoir analogs: estuarine point bar (McMurray Formation, Alberta, Canada), tidal sand ridge (Tocito Sandstone, New Mexico), and unconfined and confined tidal bars (Sego Sandstone, Utah). Estuarine point bars have long (l=67.8 m) shales that are thick and frequent relative to the other units. Tidal sand ridges have short (l=8.6 m dip orientation) shales that are thin and frequent. Confined tidal bars contain shales that are thin, infrequent, and anisotropic, averaging 16.3 m in length (dip orientation). Unconfined tidal bars contain nearly equidimensional (l=18.6 m dip orientation) shales with moderate thicknesses and vertical frequency. The observed shale geometries agree well with conceptual models for tidal environments. The unique shale character of each unit results in a different distribution of estimated . The average estimated kv/kh values for each reservoir element are: 8.2*10^4 for estuarine point bars, 0.038 for confined tidal bars, 0.004 for unconfined tidal bars, and 0.011 for tidal sand ridges. / text

The aim of this study is to present, compare and improve the options of power transmission for tidal current arrays. The potential to generate low or zero carbon power from the world’s tides is increasing as technology moves forward. The technically available tidal current energy resource, the resource that can be captured using existing technology, in the United Kingdom can supply a significant amount of the UK electricity demand. Even though tidal current devices have similarities to offshore wind turbines in many aspects, a number of characteristics differentiate the approach needed regarding power transmission and drive-train design. Some of these characteristics are: predictable direction and speed of the tidal current, predetermined available area in a tidal channel, less swept area due higher density of water, continuous underwater operation and smaller distances to shore. This thesis is based on the hypothesis that tidal current energy can be harnessed using today’s technology in an efficient manner. Technology progression never stops and as new materials and methods become available the cost of utilising tidal current energy will drop in the years to come. However, the research question that has to be asked is whether using today’s technology tidal arrays can be an alternative source of electrical power. In order to respond to this research question electromechanical models of tidal current devices have been developed in detail, from resource to the grid connection, using mathematical linear and non-linear programming in MATLAB/Simulink. The tidal models developed include the tidal resource, the tidal turbine with pitch control, geared induction and synchronous generators, the power electronics with the generator controller, the grid side controller, the cables for power transmission, the filters and the grid connection. All the modelling aspects of this study are presented in Chapter 3. Single tidal current devices were compared using different generator technologies, squirrel cage induction generator or permanent magnet synchronous generator, and different location of the power converters, in the nacelle near the generator or many kilometres apart from the generator. Regarding the generator technology, results showed that even though differences are minor, the permanent magnet synchronous generators are more efficient. Regarding the location of the power converters results showed that positioning the power converters in the nacelle always yields fewer electrical losses but component accessibility is minimised due to the underwater operation of the tidal current device. A key focus aspect of the study is the power transmission option with onshore converters which is presented in detail. Using this concept it is possible to generate electricity from tidal current devices but at the same time keep the highest possible system reliability despite the continuous underwater operation. This concept has been used in the first demonstration tidal current arrays developed by Andritz Hydro Hammerfest. What is more, data provided by Andritz Hydro Hammerfest were utilised in order to validate the simulation models. In this study a step forward is taken regarding the concept of keeping the converter dry and controlling the tidal current generator from afar. An algorithm is developed to design power harmonic filters for systems that use long distance controls. Power harmonic filters allow the long distance control system to operate reliably under all conditions but generate significant electrical losses. The power harmonic filter design algorithm presented in this thesis estimates the exact filter parameters so that the filter ensures maximum system reliability and generate minimum possible losses. In addition tidal array topologies using this concept are developed. The final part of this thesis compares a number of different tidal array topologies based on resource to grid efficiency and component accessibility for maintenance. Results showed that when tidal current devices are clustered per four turbines on offshore platforms it is efficient to use as many clusters as possible connected to a single cable whose both ends are connected to the grid. Locating the power converters in the nacelle yields fewer electrical losses compared to locating the power converters on the offshore platform. However, the difference is minimised because the distance between the tidal current device and the offshore platform is the least possible. Having the power converters on an offshore platform is beneficial in terms of accessibility for maintenance and operation because they are not underwater. The results and the methodology from this thesis can be extended to other offshore renewable energy systems such as the wind and wave. In addition, this study can be used as a stepping stone for decision making by tidal current developers.

Les espaces intertidaux correspondent à des estrans soumis à un régime de marée montrant un certain marnage. Il s’agit d’étendues basses constituées d’alluvions récentes, situées à proximité des mers à marée et envahies par les eaux lors des marées hautes. Les espaces intertidaux au nord du Vietnam sont sous l’influence de la mousson associé à un régime de marée diurne. Ils s’étendent sur environ 350 km le long de la côte. Le sud de la zone d’étude est marqué par le delta du fleuve Rouge et le fleuve Thai Binh qui apportent une grande quantité de sédiments, entraînant des estrans à dominante vaseuse ou vaso-silteuse. Le centre de la zone d’étude est caractérisé par des estrans noirs. L’exploitation du charbon dans la région de Cam Pha et de Ha Long expliquent un apport énorme de particules carbonées qui créent des estrans vaseux noirs tout à fait originaux. Cependant, les espaces intertidaux de ce secteur n’ont jusqu’à présent pas fait l’objet d’une étude détaillée. La présente thèse a pour objectif de répondre à quatre questions concernant ces espaces intertidaux :1. Comment la morphologie des estrans a-t-elle évolué depuis les 25 dernières années ?2. Quels sont les sédiments constituant ces estrans : granulométrie, teneur en carbonates, teneur en matière organique, etc. ?3. Quels sont les paramètres biophysiques de surface des estrans ?4. Quels sont les facteurs qui influencent les changements de morphologie des estrans et comment ces derniers peuvent-ils évoluer ?Afin de répondre à ces différentes questions, des images de télédétection tant optiques (Landsat, Spot, Aster, etc.) que radar (Sentinel-1A) ont été utilisées. Les analyses spatiales ont été réalisées à l’aide d’un système d’information géographique (SIG).Le présent travail est une thèse financée dans le cadre du programme liant l’Université de Sciences et Technologies de Hanoï et l’Université de Reims - Champagne-Ardenne, membre du consortium USTH. / Tidal flat is a special environment suffering tidal regime in which tidal flats are submerged during flood tide and exposing the air during ebb tide. Tidal flats in the north coast in Vietnam are constituted in diurnal tide condition with tide range varying from 0.3m to 3.5m. Along 350km coastline of the study area, the diversity of constituent conditions formed various tidal flats with different characteristic. Tidal flats in the southern part of the study area are fed by sediment from two large river systems, in the middle part forms the coal tidal flats, but the only sandy sediment along with tide domination constitute the large tidal flats in the north coast of the study area. This study apply remote sensing techniques and GIS tools to solve four scientific issues including: the evolution of tidal flats over periods from 1989 to 2014, the characteristics of sediments in tidal flats, the surface parameter of tidal flats, and the forcing factors which influence the future change of tidal flats. The results of the study shows that, tidal flats in the north coast in the study area are dramatically eroded but the tidal flats in the south coast are deposition by the concentration of fine sediments. In total 14 forcing factors, the coastal nature factor has highest forcing to the deposition of tidal flats. However, the factors of wind-wave effect and tidal flat width have negative influence to deposition. Consequently, the highest potential for future deposition of tidal flats are around the river mouths in the south coast but no potential for future deposition is in tidal flats in the north of the study area. This study is implemented in the framework of the cooperation between University of Science and Technology Ha Noi (USTH) and Université de Reims Champagne-Ardenne (URCA).

Les Pertuis Charentais sont un site d’écosystèmes interconnectés où les courants marins jouent un rôle déterminant. Un modèle de marée à haute résolution a été développé au cours de cette thèse pour comprendre et cartographier les traits principaux de la circulation hydrodynamique dans les Pertuis. Deux axes sont ainsi mis en avant dans cette étude. D’abord, un nouveau modèle de marées dans les Pertuis Charentais a été construit et validé à partir de différentes sources : données marégraphiques, données de courantomètres ADCP et images satellitaires. Une nouvelle approche de calibration de modèle de marée a été développée, basée sur la comparaison de la position de la ligne d’eau, frontière entre l’eau et la terre, avec celle prédite par le modèle. Puis dans un second temps, le transport et les agrégations en « bloom » de populations de méduses Rhizostoma, dont les proliférations et les échouages sont à l’origine de problèmes socio-économiques, ont été simulés numériquement. Des observations in situ ont permis de paramétrer le comportement de nage des méduses dans le modèle. Deux types de comportements des méduses, actif et passif ont été simulés. Les courants de marées en présence des forçages-type météorologiques ont été pris en compte. Les résultats indiquent que le comportement individuel de nage des méduses pourrait être une réponse adaptative aux facteurs abiotiques qui menacent la continuité de leur espèce mais que les courants marins restent la cause première de la formation des blooms. / The Pertuis Charentais are an interconnected ecosystems site where ocean currents play a key role. A high resolution tidal model was developed in this thesis in order to understand the main features of the hydrodynamic flows inside the Pertuis. Two topics were put forward in this study. First, a new tide model for the Pertuis Charentais was build up and validated by using different datasets: tide gauge records, measurements of currents by ADCP and satellite images. A new approach to model calibration was developed by comparing the observed position of the waterline, the boundary between land and water, with that predicted by the model. Secondly, the transport and bloom-like aggregation of the Rhizostoma jellyfish populations were simulated numerically. The jellyfish proliferation and stranding are a source of socio-economic problems. Two types of jellyfish behavior, active and passive were simulated. The tidal currents and typical meteorological forcing were taken into account. The results show that the individual behavior of swimming jellyfish is an adaptive response to abiotic factors for jellyfish survival.

Tidal power, or the use of tides for electricity production, exists in many forms including tidal barrages, which exploit tidal head differentials, and turbines placed directly in regions with large tidal current velocities. The latter is actively being investigated in many countries around the world as a means of providing renewable and wholly predictable electricity (cf. wind, solar and wave power). The expansion of the in-stream tidal industry is hindered however by several factors including: turbine durability, deployment and maintenance costs, and the lack of abundant locations which meet the necessary current velocities for turbine start-up and economic power production. A new novel type of augmentation device, entitled the ‘Tidal Acceleration Structure’ or TAS (Canadian patent pending 2644792), has been proposed as a solution to the limited number of coastal regions which exhibit fast tidal currents. In preliminary investigations, the TAS, a simple Venturi section consisting of walls extending from the seafloor to above the high water mark in an hourglass shape, was found as able to more than double current velocities entering the device. The results indicated a significant advantage over other current channeling technologies and thus the need for more in-depth investigations. The main objective of the present study was to optimise the design of the TAS and to predict the power that a turbine placed within it could extract from flow. To do this, two principal methods were employed. Firstly, a 1:50 scale model of the TAS was tested and its shape optimised in a 1.5 m wide flume. Secondly, a 3D numerical model (ANSYS Fluent) was used for comparison with the experimental results. During the tests, a TAS configuration was found that could accelerate upstream velocities by a factor of 2.12. In separate tests, turbines were simulated using Actuator Disc Theory and porous plates. The TAS-plate combination was found to be able to extract up to 4.2 times more power from flow than the stand-alone plate, demonstrating that the TAS could provide turbines with a significant advantage in slower currents. Though further research is needed, including the testing of a larger TAS model in conjunction with a small in-stream turbine, the results of this thesis clearly demonstrate the potential of the TAS concept to unlock vast new areas for tidal energy development.

No description available.

Master of Science / Department of Geology / Allen W. Archer / Abstract This study compares the tidally influenced facies found within the Tonganoxie Sandstone Member (Stranger Formation, Douglas Group) (Upper Pennsylvanian) of northeastern Kansas with similar facies directly observed in the upper intertidal mudflats of Turnagain Arm of Cook Inlet (Alaska, USA). The two settings contain strikingly similar facies that are characteristic of upper macrotidal estuaries with a strong influence of tidal activities. Identical aspects and features found within both settings include rhythmic vertical variation in stratum thicknesses (cyclic tidal rhythmites), high estimated sedimentation and aggradation rates, and biogenic and physical sedimentary structures (e.g., drag marks, raindrop impressions, arthropod traces and tetrapod trackways, zigzag burrows, runoff washouts, and upright trees, among others). Tidal rhythmites are the most important evidence that is indicative of the tidal influence on the depositional processes of these two study areas. Such cyclic tidal rhythmites have been reported and described from several Carboniferous settings in the eastern USA. Modern analogs to these Carboniferous rhythmites are usually found within upper macrotidal estuarine depositional environments, especially within fluvio-estuarine transitional zones. These environments are distributed over a wide range of modern latitudes. Using cyclic tidal rhythmites as modern analogs for interpreting similar ancient facies is a powerful tool for paleogeographic and paleoenvironmental reconstructions, although it is somewhat a new approach.