When traditional linearised theory is used to study free-surface flows past a surface-piercing object or over an obstruction in a stream, the geometry of the object is usually lost, having been assumed small in one or several of its dimensions. In order to preserve the nonlinear nature of the geometry, asymptotic expansions in the low-Froude or low-Bond limits can be derived, but here, the solution invariably predicts a waveless free-surface at every order. This is because the waves are in fact, exponentially small, and thus beyond-all-orders of regular asymptotics; their formation is a consequence of the divergence of the asymptotic series and the associated Stokes Phenomenon. In this thesis, we will apply exponential asymptotics to the study of two new problems involving nonlinear geometries. In the first, we examine the case of free-surface flow over a step including the effects of both gravity and surface tension. Here, we shall see that the availability of multiple singularities in the geometry, coupled with the interplay of gravitational and cohesive effects, leads to the discovery of a remarkable new set of solutions. In the second problem, we study the waves produced by bluff-bodied ships in low-Froude flows. We will derive the analytical form of the exponentially small waves for a wide range of hull geometries, including single-cornered and multi-cornered ships, and then provide comparisons with numerical computations. A particularly significant result is our confirmation of the thirty-year old conjecture by Vanden-Broeck & Tuck (1977) regarding the impossibility of waveless single-cornered ships.

[Truncated abstract] With rapidly increasing population densities along coastlines and rising global sea levels, coastal protection has become a major concern for coastal communities. Predicting sediment transport in nearshore regions, however, is one of the most challenging tasks faced by coastal researchers in designing coastal structures or beach nourishment schemes. Although nearshore sediment transport mainly occurs in the longshore direction, cross-shore sediment transport is crucial in determining the shoreline evolution and beach morphology . . . This study investigated the factors influencing sediment re-suspension and cross-shore suspended sediment flux in the frequency domain through a series of field measurements conducted at several different locations and a numerical model. Only oscillatory flow components were examined and the mean flow components were not considered. Although many different factors such as cross-shore location with respect to breaker line, significant wave height to water depth ratio (Hs/h), normalised horizontal velocity skewness (<u³>/‹u²›³/²), median grain size (d50), breaker type, and wave groupiness appeared to influence the magnitude of cross-shore suspended sediment flux, bed ripples was identified as the major contributing factor in changing the direction of suspended sediment flux due to incident swell waves. Moreover, the direction changed significantly with ripple type. High frequency measurements, obtained to examine the influence of turbulent kinetic energy (TKE) on higher sediment suspension events observed under wave groups indicated that higher TKE was generated at the seabed by approaching wave groups, which in turn resulted in higher suspension events.°1

In this study, available coastal models are briefly discussed and under wind waves and a numerical shoreline change model for longshore sediment transport based on &ldquo / one-line&rdquo / theory is developed. In numerical model, wave diffraction phenomenon in one-dimensional modeling is extensively discussed and to represent the irregular wave diffraction in the sheltered zones of coastal structures a simpler approach based on the methodology introduced by Kamphuis (2000) is proposed. Furthermore, the numerical model results are compared with analytical solutions of accretion and erosion at a single groin. An application to a case study of a groin field constructed to the east side of Kizilirmak river mouth, at Bafra alluvial plain, is carried out by the numerical model. The results of comparisons show that the numerical model is in good agreement with the analytical solutions of shoreline changes at a groin. Similarly, numerical model results are compared with field data of Bafra and it is shown that they are in good agreement qualitatively. Therefore, the numerical model is accepted to be capable of representing of shoreline evolution qualitatively even for complex coastal regions.

Climate change and anticipated impacts of sea level rise such as increased coastal erosion, inundation, flooding due to storm surges and salt water intrusion to freshwater resources will affect all the countries but mostly small island countries of oceans and low-lying lands along coastlines. Turkey having 8333 km of coastline including physically, ecologically and socio-economically important low-lying deltas should also prepare for the impacts of sea level rise as well as other impacts of climate change while participating in mitigation efforts. Thus, a coastal vulnerability assessment of Turkey to sea level rise is needed both as a part of coastal zone management policies for sustainable development and as a guideline for resource allocation for preparation of adaptation options for upcoming problems due to sea level rise. In this study, a coastal vulnerability matrix and a corresponding coastal vulnerability index &ndash / CVI (SLR) of a region to sea level rise using indicators of impacts of sea level rise which use commonly available data are developed. The results of the matrix and the index enable decision makers to compare and rank different regions according to their vulnerabilities to sea level rise, to prioritize impacts of sea level rise on the region according to the vulnerability of the region to each impact and to determine the most vulnerable parameters for planning of adaptation measures to sea level rise. The developed coastal vulnerability assessment model is used to determine the vulnerability of G&ouml / ksu Delta (Specially Protected Area), Mersin that has unique geological, ecological and socio-economical properties which are protected and recognized by both national and international communities.

In this study, a numerical model &ldquo / Modified Coast-Structure Interaction Numerical Model&rdquo / (CSIM) is developed with an implicit approach to determine the shoreline changes due to wind wave induced longshore sediment transport under the presence of groins, T-groins and offshore breakwaters by making modifications on the explicit numerical model &ldquo / Coast-Structure Interaction Numerical Model&rdquo / (CSI). Using representative wave data transformed to a chosen reference depth from deep water, numerical model (CSIM) simulates the shoreline changes considering structure interference. Breaking and diffraction within the sheltered zones of coastal structures defined for offshore breakwaters by using vectorial summation of the diffraction coefficients and as for T-groins shore-perpendicular part forms a boundary to define the shoreline changes seperately at two sides of the structure. Numerical model, CSIM is tested with a case study by applying in Bafra Delta, Kizilirmak river mouth at Black sea coast of Turkey. Numerical model simulations show that model results are in good agreement qualitatively with field measurements.

In this study, new design approaches are introduced for the seismic design of block type quay walls after reviewing the conventional methodologies. Within the development of the new design approaches an inverse triangular dynamic pressures distributions are applied to define both seismic earth pressures and seismic surcharge pressures. Differently from the conventional design methodology, the hydrodynamic forces are taken into consideration while dynamic forces are specified and equivalent unit weight concept is used during the both static and dynamic calculations Compatibility of this new design approaches are tested by case studies for the site and it is seen that the numerical results are in good agreement qualitatively with field measurements.

The wind and wave (wind wave/swell wave) climate has an important role in the design and operation of coastal and marine structures, harbors and ports. The objective of this study is to identify the statistical characteristics of the winds, wind waves and swell waves in Eastern Mediterranean, and coastline of T&uuml / rkiye. For this purpose, the data of wind speed and direction, swell and wind wave height, period and direction for a certain duration with the six hours time intervals are obtained from ECMWF for the wind and wave climate computations. The data covers the area of eastern Mediterranean region. In order to compute the wind and wave climate at any selected coastal location, a software is developed by Serhan Aldogan in his MSc thesis. For every location, the wind wave roses, significant height of wind wave and swell wave versus mean period of primary wind directions, extreme probability analysis and distribution, and log-linear cumulative probability analysis and distributions is presented, compared and discussed. By the help of the specifically developed software, it is possible and convenient to analyze the wind and wave climate using ECMWF data at any coordinate.

Block type quay walls are commonly used as berthing structures both in Turkey and worldwide. In this study, stability analysis of block type quay wall is carried out using pseudo-static method. A computer program named QSAP (using Excel spreadsheet) has been developed for the design of block type quay walls. QSAP has been prepared based on the rules of Turkish Seismic Design Codes for Coastal Structures, 2008. Reliability of this program is verified by a comparative study of Derince Port block type quay wall, damaged in Marmara earthquake (1999), with manual solution and field measurements. A newly introduced placement methodology &ldquo / Knapsack&rdquo / is also studied with QSAP and the results are compared with the conventional placement method.

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.

In this thesis, the wind-wave records obtained at three locations along the Turkish coasts (Alanya, Dalaman and Hopa) are analyzed. Probability distributions of individual wave characteristics (wave height, wave period and wave steepness) are obtained and compared with the model distributions. Goodness of fit of the observed distributions is checked by Chi-square test and Kolmogorov-Smirnov tests. Joint probability distribution of individual wave heights and periods is also studied and compared with the theoretical distributions. The relationships among various statistical wave height parameters and statistical wave period parameters are investigated and compared with the theoretical and reported values.