The flow field behavior in the vicinity of a perforated breakwater and the efficiency of the breakwater under regular waves were studied. To examine the efficiency of the structure thirteen types of regular wave conditions with wave periods T = 1, 1.2, 1.6, 2, 2.5 sec and wave heights Hi = 2, 4, 6, 8, 10 cm in an intermediate water depth of 50 cm were tested. The incoming, reflected and transmitted wave heights were measured using resistance type wave gauges positioned at the required locations. The efficiency of the structure was calculated considering the energy balance for the system. The efficiency of the structure for different wave conditions and with different parameters are shown and compared. Seven types of regular waves with wave periods T = 1, 1.6, 2, 2.5 sec and wave heights Hi = 4, 6, 8, 10 cm in an intermediate water depth of 50 cm were tested for the flow behavior study. In order to study the flow field variation with phase, ten phases were considered per one wave. The Particle Image Velocimetry (PIV) technique was employed to measure the two dimensional instantaneous velocity field distribution and MPIV (Matlab toolbox for PIV) and DaVis (a commercial software) were used to calculate the velocity vectors. By repeating the experiments and taking an average, the mean velocity field, mean vorticity field, mean turbulent intensity and mean turbulent kinetic energy field were calculated for each phase and for each wave condition. The phase average fields for each wave condition for each of the above mentioned parameters were calculated taking the average of ten phases. The phase averaged velocity, vorticity and turbulent kinetic energy fields are presented and compared. The energy dissipation based on both elevation data and the velocity data are presented and compared. It was found that for more than 75% of the tested wave conditions, the energy dissipation was above 69%. Thus the structure is very effective in energy dissipation. Further it was found that for all the tested wave conditions most of the turbulent kinetic energy form near the free surface and near the front wall, where as behind the back wall of the structure the turbulent kinetic energy was very small.

Abstract The purpose of this research is to evaluate the tension variation of mooring rope on the floating breakwater made of abolish tires and the efficiency of wave elimination under the interaction of wave and water current. It has been shown that using the mooring rope system could reduce 56% instantaneous tension of the floating breakwater under the interaction. The mooring rope system on the floating breakwater had the maximum efficiency of wave elimination with low flow velocity (V) and high wave height (H). For instance, when V was 5 cm/sec and H was 15 cm, I found when the attack anger was 45¢X, 60¢X, or 90¢X, the efficiency of wave elimination was 73.7%, 72.10%, or 73.2% respectively. However, the efficiency of wave elimination was lower when V and H were high. For instance, when V was 15 cm/sec, H was 10 cm and the attack anger was 90¢X, the efficiency of wave elimination was only 40%. The efficiency of wave elimination was generally about 50% under other conditions. Therefore, the floating breakwater with mooring rope system apparently has high practical function and value.

The flow field behavior in the vicinity of a perforated breakwater and the efficiency of the breakwater under regular waves were studied. To examine the efficiency of the structure thirteen types of regular wave conditions with wave periods T = 1, 1.2, 1.6, 2, 2.5 sec and wave heights Hi = 2, 4, 6, 8, 10 cm in an intermediate water depth of 50 cm were tested. The incoming, reflected and transmitted wave heights were measured using resistance type wave gauges positioned at the required locations. The efficiency of the structure was calculated considering the energy balance for the system. The efficiency of the structure for different wave conditions and with different parameters are shown and compared. Seven types of regular waves with wave periods T = 1, 1.6, 2, 2.5 sec and wave heights Hi = 4, 6, 8, 10 cm in an intermediate water depth of 50 cm were tested for the flow behavior study. In order to study the flow field variation with phase, ten phases were considered per one wave. The Particle Image Velocimetry (PIV) technique was employed to measure the two dimensional instantaneous velocity field distribution and MPIV (Matlab toolbox for PIV) and DaVis (a commercial software) were used to calculate the velocity vectors. By repeating the experiments and taking an average, the mean velocity field, mean vorticity field, mean turbulent intensity and mean turbulent kinetic energy field were calculated for each phase and for each wave condition. The phase average fields for each wave condition for each of the above mentioned parameters were calculated taking the average of ten phases. The phase averaged velocity, vorticity and turbulent kinetic energy fields are presented and compared. The energy dissipation based on both elevation data and the velocity data are presented and compared. It was found that for more than 75% of the tested wave conditions, the energy dissipation was above 69%. Thus the structure is very effective in energy dissipation. Further it was found that for all the tested wave conditions most of the turbulent kinetic energy form near the free surface and near the front wall, where as behind the back wall of the structure the turbulent kinetic energy was very small.

The aim of this investigation was to measure and analyse wave loading on a full scale coastal structure in order to validate current breakwater design methods and to improve understanding of the physical processes involved. A range of new, robust field measurement instrumentation was developed and deployed at the chosen field site, the Alderney Breakwater in the Channel Islands. The instrumentation deployed in this particularly harsh wave loading environment included an array of wave loading pressure sensors together with co-located void fraction gauges, which were used to measure the percentage air entrained within the seawater. Wave data was measured by means of a sea bed array of six pressure sensors which were logged using an underwater data logger. Data from the instrumentation mounted on the breakwater wall was logged with a high specification remote data logger. Both the instrumentation and the data acquisition equipment were developed and adapted specifically for this investigation and as a result over 150 high quality data sets were recorded at very high logging rates, which allowed field data analysis at an unprecedented level. New calibration and data processing methods were developed for the analysis of this novel set of data records. Due to the meticulous planning, instrument development, data acquisition development, and deployment the data collected is, to the best of the Author's knowledge, the highest quality wave loading field data collected to date. The wave conditions measured at the site were used as inputs to three commonly used design methods for vertical coastal structures, which were used to estimate the maximum wave loading pressures over the height of the structure. The pressures and forces predicted by the models were contrasted with measured values and it was found that the Goda method (1985) predicted the events with a high degree of accuracy provided that the waves were not breaking directly onto the structure. When waves did break onto the structure high magnitude, short duration pressures were frequently measured which sometimes also acted over a very small spatial area. There was a large degree of temporal and spatial variability in the high magnitude breaking wave pressures and they were not accurately predicted by any of the models. The relationship between wave momentum flux and wave loading impulse was investigated both on a record by record basis and using a wave by wave analysis. For the Alderney field site a consistent relationship was found between the wave momentum flux and wave loading impulse, which could be used to estimate the wave loading impulse and duration for known wave input conditions. Features of interest were also identified from temporal comparisons of individual co-located pressure and aeration traces, including negative pressures and a negative correlation between air content and pressure over short time scales.

This thesis presents an original theoretical investigation, based on diffraction theory (extended for permeable structures by Sollitt & Cross [56]), of the performance of segmented rubble mound breakwaters. The amount of protection offered by such a breakwater is a function of the rubble construction (characterized by porosity and permeability), geometry and spacing of segments as well as depending on the the characteristics of the incident wave field. To explore the influence of these factors on the performance of these breakwaters, the diffraction by three related structures have been considered :a periodic array of impermeable blocks, a single continuous rectangular section permeable structure and a periodic array of permeable blocks in shallow water.

The performance of a flexible structure as a breakwater is investigated numerically. The structure is a hemicylinder and is filled with water of uniform pressure. It is anchored along the sides. Only flexural modes are present. The structure is modeled as an elastic shell using the finite element program ABAQUS. The fluid is assumed to be inviscid and incompressible. The fluid flow is analyzed using a boundary integral method and the integral equation is solved numerically by a panel method. The vibration characteristics of the structure are analyzed both in the absence and presence of water. The hydrodynamic coefficients, forces, and the dynamic response of the structure in waves are obtained as a function of the wave number. Two different water depths of 5 m and 6 m are considered. For each water depth, normal and oblique incident waves are considered. The free surface elevation in front of and behind the structure is evaluated for different wave frequencies and directions. The results indicate that the flexible structure is effective in reducing the incident wave intensity over a wide range of frequencies. / Master of Science

The Cleveland Harbor East Breakwater, Cleveland, OH, rehabilitation was completed in 1980. The easternmost 4,440ft (1,341m) was armored with 29,741 two ton (1,814kg) dolosse, slender concrete armor units (CAU) used on coastal structures since 1964. The armor structurally failed within 33 years, a relatively short life for CAU structures. This thesis re-examines the monitoring data from rehabilitation to failure to investigate the deterioration of the armor layer up to the Hurricane Sandy related storm event and includes new information to correlate the remnants of Hurricane Sandy to dolos armor damage that was significant enough to require a new rehabilitation. Probable causes of dolos failures at Cleveland include underdesign, forcing stresses, settlement, ice pressure, continuous surface wave action and extreme storm events. The conditions during the Hurricane Sandy 100-year storm event included a 2 to 3ft (0.6 to 0.9m) storm surge, significant wave heights of 17.4ft (5.3m) and 9.2sec significant wave periods. Post-storm monitoring reinforced the acceptance that most, if not all, new significant dolos damage was the result of the remnants of Hurricane Sandy, resulting in areas of catastrophic armor unit failure along the 1979-1980 dolosse rehabilitation section of the Cleveland Harbor East Breakwater.

The purpose of this study was to evaluate the local and regional processes causing the shoreline recession of an eroding beach/berm/wetland system on the eastern shore of Mobile Bay. The analysis was then used to evaluate different technologies which could meld to create a holistic shoreline protection design to fortify the entire spectrum of the shoreline. Wind waves are the major erosional force causing a bi-directional, but southerly dominated, longshore transport and an erosional cross-shore transport during large wave events. Erosion mitigation technologies which promote ecological integrity are presented and include: oyster shell breakwaters, SAV establishment, intertidal grass plantings, and tree and shrub plantings. By combining these technologies, a plan which mitigates erosion as well as greatly increases the health of the local ecosystem can be formed. By fortifying in this manner the shoreline and its communities can be more resilient and prepared for future climatological changes and conditions.

For oblique and normal water waves at various frequencies, the use of moored cylinders as breakwaters is considered numerically using linear three-dimensional analysis. The breakwater can be used by itself for protection of small structures or as a series of cylinders to protect a harbor, shoreline, or moored vessel from the destructive energy associated with incident water waves. The breakwater is completely submerged below the free surface and is attached to the ocean floor with six symmetrically configured mooring lines. The cylinder is filled with air and the mooring lines remain taut during the structure's motion. Six degrees of freedom describe the motion of the breakwater and additional degrees of freedom are introduced as the cables are modeled with the use of lumped masses connected with springs. The fluid is assumed to be inviscid and incompressible, so that the velocity field can be written as the gradient of the velocity potential. A boundary integral method is used to solve the integral equations that define the external fluid flow. Free vibrations of the cylinder in both air and water are considered and "dry " and "wet" natural frequencies are computed. Motions caused by water waves are studied to establish the effect of certain parameters on the effectiveness of the breakwater. The transmission coefficient is shown to be somewhat misleading when compared to plots that show the spatial variation of the wave amplitude. / Master of Science

­^¤åºK­n A time-independent finite-difference numerical scheme is developed to study the dynamic response of a submerged and a floating breakwater under the wave loading of a fully numerical force. The coupled surge, heave and pitch motion of a floating breakwater and the wave-structure interaction are included in the model. The numerical results are validated uses several bench mark studies and results available elsemlse. The wave reducing effect of a submerged and a floating breakwaters were analysis and discusse.