This thesis presents an examination of the nearshore wave bottom boundary layer under conditions of significant sediment response. Using both field observations and simple models, the response of the bottom boundary layer to random waves is shown to have a complex behavior. First, the linearized wave bottom boundary layer governing equation is solved with a transformation of the cross-shore velocity to a distorted spatial domain, resulting in an analytic expression for the temporal and vertical structure of the cross-shore velocity under an arbitrary wave field. Model predictions of the bed shear velocity are in good agreement with laboratory measurements. The model is limited by assuming zero velocity at a fixed bed and that turbulence generation is solely due to bottom shear. Next, a comprehensive set of near bed cross-shore velocity, sediment suspension, and bed elevation observations, collected in 2 m water depth on the North Carolina coast, are presented. The observations show a cross-shore velocity structure which decays with increasing proximity to the bed as predicted by simple theory. Bottom shears based on rms amplitude decay and time-averaged phase shifts are lower than model predictions and may be indicative of more rapid mixing of momentum than assumed in the above model. Also, frequency-dependent estimates of the phase and amplitude vertical structure show a nonlinear response of the wave bottom boundary layer over the incident band. Through most flow phases, estimates of turbulent kinetic energy increase linearly from the bed, however under large wave crests, enhanced turbulence levels are observed and are well correlated to active sediment suspension events. Estimates of dissipation rates are significantly less than those observed in an actively breaking surf zone wave, and significantly greater than those observed in ocean boundary layers, and continental shelf current boundary layers. Finally, an Oregon coast field experiment showed an intermittent high frequency velocity variance structure which was correlated to suspended sediment events. A linear shear instability analysis determined that during the period of flow reversal there exists a potential for generating turbulence due to shear instabilities of the vertical structure of cross-shore velocity. / Graduation date: 1997

Graduation date: 1982

Graduation date: 2006

Not available / text

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 241-244. / by Dale B. Haidvogel. / Ph.D.

This investigation is concerned with the determination of the sea state in terms of wave spectra. The phenomenon was calculated for two different bathymetries. The purpose is to develop a finite difference method with an upwind differencing scheme to g solve several formulations of the wave action conservation equation. The computations were done in the wave number space and the frequency direction space. For the case of a beach with constant slope the results were compared with the analytical solution. For the case of an elliptical submerged shoal, they were compared with experimental data. The results of the computer code showed a fairly good qualitative agreement with the actual values for a smooth distribution of input energy. / Master of Science

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 (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1980. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 196-201. / byLee-Lueng Fu. / Ph.D.

In the present dissertation, the hydrodynamic and hydro-elastic characteristics of ship hull and plate vibrations are analyzed using theoretical and numerical methods. The wave forces are determined using a suite of methods which include the Froude-Krylov method for incident wave forces, Wagner's method and ABS rules for the slamming wave force, and numerical methods for nonlinear wave radiation forces. Finite difference methods are developed to determine the wave forced vibrations of ship hull plates which are modeled using a range of plate theories including nonlinear plate theory with and without material damping and orthotropic plate theory for stiffened hull plates. For small amplitude deformation of thin plates, a semi-theoretical superposition method is used to determine the free and forced vibrations. The transient ship hull vibration due to whipping is also analyzed using the finite difference method. Results, in the form of deformations and stress distributions, are obtained for a range of scantling and wave parameters to identify key parameters to consider in ship structural design. / by Fnu Lakitosh. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

Thesis (S.M.)--Joint Program in Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering, and the and Woods Hole Oceanographic Institution), 2000. / Includes bibliographical references (p. 100-101). / A finite difference computer model is developed to simulate the exposure statistics of a radio frequency buoyant antenna as it is towed in a three-dimensional random seaway. The model allows the user to prescribe antenna properties (length, diameter, density, etc.), sea conditions (significant wave height, development of sea), tow angle, and tow speed. The model then simulates the antenna-sea interaction for the desired duration to collect statistics relating to antenna performance. The model provides design engineers with a tool to predict antenna performance trends, and to conduct design tradeoff studies. The floating antenna envisioned is for use by a submarine operating at modest speed and depth. / by Sam R. Geiger. / S.M.