Thesis (Ph. D.)--University of Hawaii, 1998. / Includes bibliographical references (leaves 124-132).

Thesis (M.S.)--Naval Postgraduate School, 1988. / Cover title. "June 1988." Includes bibliographical references (p. 194-202).

Thesis (Ph. D.)--Johns Hopkins University, 1996. / Vita. Includes bibliographical references (leaves 137-150).

Includes bibliography. / Ocean waves represent an important design factor in many coastal engineering applications. Although extreme wave height is usually considered the single most important of these factors there are other important aspects that require consideration. These include the probability distribution of wave heights, the seasonal variation and the persistence, or duration, of calm and storm periods. If one is primarily interested in extreme wave height then it is possible to restrict one's attention to events which are sufficiently separated in time to be effectively independently (and possibly even identically) distributed. However the independence assumption is not tenable for the description of many other aspects of wave height behaviour, such as the persistence of calm periods. For this one has to take account of the serial correlation structure of observed wave heights, the seasonal behaviour of the important statistics, such as mean and standard deviation, and in fact the entire seasonal probability distribution of wave heights. In other words the observations have to be regarded as a time series.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2002. / 198 leaves double sided printed, preliminary pages i-xx and numberd pages 1-1-12-6.Includes bibliography. List of tables, figures and appendices and acronyms. Scanned with a HP Scanjet 8250 Scanner to pdf format (OCR). / ENGLISH ABSTRACT: In this study the numerical short wave model SWAN is evaluated for application to a selected coastal region in South Africa. The aim of this study was to evaluate the degree of accuracy with which SWAN can simulate prototype nearshore wave spectra and wave parameters (e.g. wave height, mean wave direction and mean wave period) for an Algoa Bay field case. Algoa Bay represents a typical deep, sheltered embayment on the South African south coast, which is exposed to high-energy swell. Sensitivity analyses on various wave-related processes were also done, with the aim of establishing the dominant physical processes and appropriate model setup for the Algoa Bay field case. With the dominant wave-related processes and appropriate model setup for the Algoa Bay field case established, selected final runs were performed to determine the degree of accuracy with which SWAN can simulate prototype conditions, by comparing its results with available field recordings. This study comprises a review of the SWAN evaluation work conducted to date by others, an overview of South African coastal conditions, and numerical model simulations. The model simulations, which represent the main focus of this study, were conducted for a selection of available offshore wave conditions (at 85 m water depth) observed during the Algoa Bay field case and were compared to available nearshore observations (at 17 m water depth). Environmental conditions of waves, wind and currents were included in these simulations. The study focuses on model application and sensitivity analysis, rather than model development, and includes evaluation of all relevant processes, without focussing on any specific model aspect. The results of this study show that SWAN simulations correlated well with observations at the nearshore station in Algoa Bay, both in wave spectral shape and its associated parameters. Dominant processes identified for the field case were depth-induced refraction, bottom friction and directional spreading. This finding agrees with those of previous evaluations of SWAN and previous modelling experience by others. It is shown that high-energy swell is relatively more sensitive to the choices of model setup than wind sea. Based on the simulation results of high-energy swell, it is concluded that the calculation of depth-induced refraction in SWAN seem to contain a degree of inaccuracy. It is also concluded that the findings of this study could be used as a guideline to SWAN modelling studies along the South African south coast. / AFRIKAANSE OPSOMMING: In hierdie studie word die toepassingsmoontlikhede van die numeriese kortgolf model SWAN vir 'n geselekteerde gedeelde van die Suid-Afrikaanse kuslyn beoordeel. Die doel van hierdie studie is om die vlak van akkuraatheid waarmee SWAN prototipe golfspektra en golfparameters (bv. golfhoogte, gemiddelde golfrigting en gemiddelde golfperiode) in die vlakwater kan simuleer te beoordeel, vir 'n Algoabaai gevallestudie. Algoabaai verteenwoordig 'n tipiese diep, beskermde baai aan die Suid-Afrikaanse kuslyn, wat blootgestel is aan hoe-energie deining. Sensitiwiteitstoetse is ook uitgevoer vir verskillende golfprosesse, met die doel om die dominante fisiese prosesse en gepaste modelopstelling vir die Algoabaai gevallestudie te vind. Nadat die dominante golfprosesse geidentifiseer is, en die toepaslike modelopstelling gevind is, is finale simulasies uitgevoer vir geselekteerde gevalle om die mate van akkuraatheid te bepaal waarmee SWAN prototipe kondisies kan simuleer, deur simulasie resultate met beskikbare veldmetings te vergelyk. Hierdie studie bestaan uit 'n samevatting van die evaluasiewerk verrig op SWAN deur andere, 'n samevatting van golf-, wind- en stroomtoestande aan die Suid-Afrikaanse kus en numeriese modelsimulasies. Die modelsimulasies, wat die hooffokus van hierdie studie is, is uitgevoer vir 'n seleksie van beskikbare diepsee golftoestande (in 85 m waterdiepte) uit die Algoabaai gevallestudie en is vergelyk met beskikbare vlakwater metings (in 17 m waterdiepte). Omgewingstoestande van golwe, wind en seestrome is ingesluit in hierdie simulasies. Die studie fokus op modeltoepassing en sensitiwiteits-analise, eerder as modelontwikkeling, en behels die beoordeeling van alle toepaslike modelprosesse, sonder om te fokus op enige spesifieke model aspek. Die resultate van hierdie studie toon aan dat die SWAN simulasies goed korrileer met vlakwater meetings in Algoabaai, vir beide golfspektraalvorm en verwante golfparameters. Bodemrefraksie, bodemwrywing en rigtingsspreiding is geidentifiseer as dominante modelprosesse. Hierdie resultaat kom ooreen met bevindings van vroeere beoordeling van SWAN en modelleer-ervaring deur andere. Dit word aangetoon dat hoe-energie deining relatief meer sensitief is vir modelopstelling as wind-see. Gebasseer op resultate van simulasie met hoe-energie deining, word die gevolgtrekking gemaak dat die berekening van bodemrefraksie in SWAN 'n mate van onakkuraatheid toon. Die gevolgtrekking word ook gemaak dat die resultate van hierdie studie as riglyn gebruik kan word vir modelleerwerk met SWAN aan die Suid-Afrikaanse suidkus.

Large beach cusps with wavelengths O(200m), sometimes termed mega-cusps, were measured along 18km of the Southern Monterey Bay coastline from October 2004 to April 2005 to investigate the cuspate shoreline response to rip current systems. Monterey Bay is a unique location for the study of rip current systems, which has with well defined rips that are present all year long, a large dune erosional rate, and incident wave energy that is primarily shore-normal with a large alongshore gradient. Contours of the coastline were extrapolated from the surveys using an all-terrain vehicle equipped with Kinematic GPS. Cusp spacing was inferred from the data using a zero up-cross technique and found to be O(230m) for low wave energy beaches and O(250m) for high wave energy beaches. Migration rates of the cusps were found to be 1-5m/day owing to the quasi-uniform erosion of the dune system. Cusps were found to be semi-permanent features with length scales dependant upon the local wave climate.

CIVINS / The understanding of large and rare waves in the ocean is becoming more important as these rare events are turning into more common observances. In order to design a marine structure or vehicle to withstand such a potentially devastating phenomenon, the designer must have knowledge of extreme waves with return periods of 50 and 100 years. Based on satellite radar altimeter data, researchers have successfully predicted extreme significant wave heights with the return periods of 50 and 100 years. This thesis extends their research further by estimating the most probable extreme wave heights and other wave statistics based on spectral analysis. The same technique used for extreme significant wave height prediction is applied to extrapolation of corresponding mean wave periods, and they are used to construct two parameter spectra representing storm sea conditions. The prediction of the most probable extreme wave heights as well as other statistical data is based on linear theory and short term order statistics. There exists sufficient knowledge of second order effects on wave generation, and it could be applied to a logical progression of the simulation approach in this thesis. However, because this greatly increases computation time, and the kinematics of deep sea spilling breakers are not yet fully understood for which substantial new research is required, the nonlinear effects are not included in this thesis. Spectral analysis can provide valuable statistical information in addition to extreme wave height data, and preliminary results show good agreement with other prediction methods including wave simulation based on the Pierson-Moskowitz spectrum. / Contract number: N662271-97-G-0025 / CIVINS / US Navy (USN) author

CIVINS / The United States Navy has taken a new interest in tumblehome hulls. While the stealth characteristics of these hull forms make them attractive to the Navy, their sea keeping characteristics have proven to be problematic. Normal approximations of sea keeping characteristics using linear differential equations with constant coefficients predict a very stable platform, while observations in model tests show a ship that is prone to extreme roll transients. This thesis examines a simple method of producing a non-linear simulation of roll motion using a tumblehome hull provided by the Office of Naval Research. This research demonstrates the significant difference that a variable restoring coefficient introduces into a hull's seakeeping characteristics. / Contract number: N62271-97-G-0026 / CIVINS

Approved for Public Release; Distribution is Unlimited / Littoral waters when compared to the open ocean create an environment of greater reverberation with acoustic energy scattering from the sea surface, bottom, topographic features, and regions that lack homogeneity within the volume. If the ocean surface is rough on the scale of an acoustic wavelength, considerable scattering can occur that can significantly influence coherent propagation. Because the rough surface is also evolving dynamically, such scattering can introduce Doppler shifting and spreading of the acoustic pulse spectrum. This thesis builds upon prior efforts in ocean acoustic modeling and is focused on examining surface scattering and its affect upon coherent propagation. The dynamics/physics associated with surface scattering are explored in detail and mathematical relationships are developed and employed in revisions to the Monterey Miami Parabolic Equation (MMPE) model. The thesis provides background information associated with the MMPE and highlights earlier work related to surface scattering. It presents a formal analysis of an exact surface scattering approach in the context of a continuous wave (CW) benchmark exercise and the Doppler shifts associated with a dynamic rough surface. It expands on prior rough sea surface work to include modeling based on an empirical fetch-limited ocean wave spectrum and compares modeling results with measured data. Interest in broadband pulse propagation in shallow water is increasing with the need for improved active sonar systems and with the growth of applications such as underwater acoustic communications. / Naval Undersea Warfare Center Division Newport

The aim of this project is to identify the effect of wind on near-shore breaking waves. A breaking wave was created using a simulated beach slope configuration. Testing was done on two different beach slope configurations. The effect of offshore winds of varying speeds was considered. Waves of various frequencies and heights were considered. A parametric study was carried out. The experiments took place in the Hydrodynamics lab at FAU Boca Raton campus. The experimental data validates the knowledge we currently know about breaking waves. Offshore winds effect is known to increase the breaking height of a plunging wave, while also decreasing the breaking water depth, causing the wave to break further inland. Offshore winds cause spilling waves to react more like plunging waves, therefore increasing the height of the spilling wave while consequently decreasing the breaking water depth. / by Faydra Schaffer. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.