Typescript. Bibliography: leaves 145-150.

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

The fractal dimension of measured ocean wave profiles is found to be in the range of 1.5-1.8. This non-integer dimension indicates the fractal nature of the waves. Standard formulations to analyze waves are based on a differential approach. Since fractals are non-differentiable, this formulation fails for waves with fractal characteristics. Integral solutions for long waves that are valid for a non-differentiable fractal surfaces are developed. Field observations show a positive correlation between the fractal dimension and the degree of nonlinearity of the waves, wave steepness, and breaking waves. Solutions are developed for a variety of linear cases. As waves propagate shoreward and become more nonlinear, the fractal dimension increases. The linear solutions are unable to reproduce the change in fractal dimension evident in the ocean data. However, the linear solutions do demonstrate a finite speed of propagation. The correlation of the fractal dimension with the nonlinearity of the waves suggests using a nonlinear wave equation. We first confirm the nonlinear behavior of the waves using the finite difference method with continuous function as the initial condition. Next, we solve the system using a Runge-Kutta method to integrate the characteristics of the nonlinear wave equation. For small times, the finite difference and Runge-Kutta solutions are similar. At longer times, however, the Runge-Kutta solution shows the leading edge of the wave extending beyond the base of the wave corresponding to over-steepening and breaking. A simple long wave solution on multi-step bottom is developed in order to calculate the reflection coefficient for a sloping beach. Multiple reflections and transmissions are allowed at each step, and the resulting reflection coefficient is calculated. The reflection coefficient is also calculated for model with thousands of small steps where the waves are reflected and transmitted once over each step. The effect of depth-limited breaking waves is also considered. / Graduation date: 2003

This report details the derivation of an analytical model for a flexible membrane wave barrier. The wave barrier consists of a thin flexible membrane suspended in the water column by a moored cylindrical buoy on the free surface and fixed to a hinge at the seafloor. The analytical model combines the three-degree of freedom rigid body motion of the cylindrical buoy with the two-dimensional analog of a vibrating string for the response of the flexible membrane. Theoretical results for reflection and transmission coefficients, dynamic mooring line tension, horizontal hinge force, horizontal and vertical displacements and rotation of the cylindrical buoy are compared with measured results presented by Bender(1989). In general, the theoretical results compare favorably with measured results for moored systems. However, additional studies are required to more precisely quantify the added mass and radiation damping properties of flexible membranes in oscillating flows. / Graduation date: 1991

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published_or_final_version / abstract / toc / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Mechanical Engineering / Doctoral / Doctor of Philosophy

Typescript. / Thesis (Ph.D.)--University of Hawaii, 1985. / Bibliography: leaves 132-136. / Photocopy. / xxiii, 136 leaves, bound ill. 29 cm

A time-domain model was developed to predict the fluid/structure interaction of a three-dimensional deformable body in a fluid domain subject to long-crested finite amplitude waves. These nonlinear waves induce transient motion in the body. In turn, the interaction of the body with the waves modifies the wave field, causing additional motion in the body. A time-domain simulation was required to describe these nonlinear motions of the body and the wave field. An implicit three-dimensional time-domain boundary element model of the fluid domain was developed and then coupled iteratively with a finite element model of the deformable body. Large body hydrodynamics and ideal fluid flow are assumed and the diffraction/radiation problem solved. Either linear waves or finite amplitude waves can be treated in the model. Thus the full nonlinear kinematic and dynamic free surface boundary conditions are solved in an iterative fashion. To implicitly include time in the governing field equations, Volterra's method was used. The approach is similar to that of the typical boundary element method for a fluid domain where the boundary element integral is derived from the governing field equation. The difference is that in Volterra's method the boundary element integral is derived from the time derivative of the governing field equation. The transient membrane motions are treated by discretizing the spatial domain with curved isoparametric elements. Newton-Raphson iterations are used to account for the geometric nonlinearities and the equations of motion are solved using an implicit numerical method. Examples are included to demonstrate the validity of the boundary element model of the fluid domain. The conditions in a wave channel were numerically modeled and compared to sinusoidal waves. The interaction of a submerged rigid horizontal cylinder with water waves was modeled and results compared to experimental and numerical results. The capability of the model to predict the interaction of highly deformable bodies and water waves was tested by comparing the numerical model to large-scale physical model experiment of a membrane cylinder placed horizontally in a wave channel. / Graduation date: 1992

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