Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 117-127). Also available in electronic version.

This thesis addresses the general problem of vorticity waves propagating over steeply sloping topography, in the presence of stratification and rotation. From the inviscid unforced long-wave equations for a two-layer fluid on an f-plane, it is shown that, as long as the ratio of the upper to lower layer depths is small, semi-enclosed and enclosed basins can sustain low-frequency, short scale, surface-intensified motions. Simple analytical solutions are to be found only if the upper to lower layer depths ratio is small. Then, we obtain a set of equations which describes a barotropic wave which forces a baroclinic response through topographic coupling. Two bottom profiles are considered: linear and parabolic. Solutions are found with and without the small slope approximation. It is shown that the small slope approximation underestimates all the parameters of low-frequency topographic waves, even when the slope is small. The theory is compared with observations from the Strait of Georgia and with a numerical model of the Saint Lawrence estuary. It is found that, for bathymetric profiles similar to those of the Strait of Georgia (linear) and the Saint Lawrence (parabolic), bur model provides a better fit to the topography, leads to surface-intensified motions and produces cross-channel velocities very similar to those observed in situ. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Best M.Phil Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize,2005-2006 / published_or_final_version / abstract / Mechanical Engineering / Master / Master of Philosophy

The goal of this research project is to determine the fractal nature, if any, which certain surface water waves exhibit when viewed on a microscopic scale. We make use of the mathematical formulation of non-viscous fluids describing their physical properties. Using these expressions and including boundary conditions for free surfaces as well as taking the surface tension into consideration, we obtain a partial differential equation describing the dynamics of surface water waves. A brief introduction to the study of fractal geometry with several examples of well-known fractals is included. An important property of fractals is their non-integral dimension. Several methods of determining the dimension of a curve are described in this paper. Our wave equation is examined under different assumptions representing the conditions of a surface water wave near its breaking point. Solutions are developed using analytical and numerical methods. We determine the dimension of 'rough' solutions using one of the methods introduced and conclude that under certain conditions, surface water waves near their breaking point exhibit a fractal structure on a microscopic scale. / Graduation date: 1994

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 70-74). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--Drexel University, 2003. / Includes abstract and vita. Includes bibliographical references (leaves 125-135).

Impulse waves in reservoirs, lakes, bays and oceans may be generated by landslides. The resulting impulse waves can propagate and cause disaster to the downstream. Some studies are carried out to investigate such phenomenon but most of them were based on either experimental observations or empirical/semiempirical relationships in simulating the waves generated by landslides. Therefore, the fundamental mechanism of such hazard is not got fully understood (complex motions of landslides with arbitrary geometry and interactions of fluid with landslides or shorelines). In addition, the effects of landslide-induced waves on downstream structures are rarely reported. Therefore, it appears necessary that the coupling numerical model is developed to simulate landslide-induced waves and to investigate generated wave characteristics. Furthermore, their effects on downstream structures should be investigated for mitigating hazard, such as the estimations of wave run-up, rundown and wave overtopping. This thesis presents the numerical modeling of landslide-induced waves and their effects on the downstream structures based on the computational fluid dynamics (CFD) package FLUENT. As there is no existing module to simulate water waves, the redevelopment of FLUENT by the user defined function (UDF) is necessary. For the problem of landslide-induced wave, two simplified numerical models are developed, including piston-type model and inlet boundary-type model. These two numerical models can rapidly assess the landslide-induced waves but be appropriate for the simple cases, such as a vertical wall moving horizontally or slump-type landslide whose particle velocities and free surface displacements at the inlet boundary are known. In order to expand the available range of numerical modeling, the block models aiming for rockslide are developed to investigate landslide-induced waves. Four categories of landslides are considered, such as horizontal landslide, vertical landslide, subaerial landslide and submarine landslide. Except of horizontal landslide, the coupled block model is employed to investigate water waves generated by vertical, subaerial and submarine landslides. The coupling is based on an iterative procedure enforcing the principle of the dynamic equilibrium of the fluid, the slide and their interfaces, and the interaction between landslide and fluid are considered. The wave characteristics generated by above-mentioned different types of landslides are investigated and discussed. For their effects of landslide-induced wave on downstream structures, the focuses of numerical modeling are the run-up and rundown of waves generated by subaerial and submarine landslides and wave overtopping on the downstream structures. The detailed numerical modeling illustrates that the present models can predict fairly well landslide-induced waves and their effects on downstream structures. The results of parametric study indicate that slide volume and impact Froude number ( v / gh ) play important roles on generated wave characteristics. The wave characteristics, propagation distance and geometric characteristics of seaward structural wall (slope and crest freeboard) are major factors in determining the characteristics of wave run-up, rundown and overtopping. Several useful prediction relationships are provided. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

No description available.

Diffraction of regular waves, focused wave groups, and random seas by arrays of vertical bottom mounted circular cylinders is investigated using theoretical, computational, and experimental methods. Free surface elevation η is the defining variable used to test the potential theory developed. In addition, the nonlinearity of focused wave groups is investigated through the Creamer nonlinear transform and analysis of numerical wave tank data. Linear focused wave group theory is reviewed as a method for predicting the probable shape of extreme events from random wave spectra. The Creamer nonlinear transform, a realistic model for steep waves on deep water, is applied in integral form to simulate nonlinear focused wave groups. In addition, the transform is used to facilitate analysis of nonlinear wave-wave interactions within focused wave groups from a uni-directional numerical wave tank developed at Imperial College London. Experiments in an offshore wave basin at HR Wallingford are designed to measure free surface elevation at multiple locations in the vicinity of a multicolumn structure subjected to regular and irregular waves for a range of frequencies and steepness. Results from regular wave data analysis for first order amplitudes are compared to analytical linear diffraction theory, which is shown to be accurate for predicting incident waves of low steepness. However, second and third order responses are also computed, and the effects in the vicinity of a second order near trapping frequency are compared to semi-analytical second order diffraction theory. Analytical linear diffraction theory is extended for application to focused wave groups and random seas. Experimental irregular wave data are analysed for comparison with this theory. Linear diffraction theory for random seas is shown to give an excellent prediction of incident wave spectral diffraction, while linear diffraction theory for focused wave groups works well for linearised extreme events.