Document Type

Thesis - University Access Only

Award Date

2003

Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

First Advisor

Francis C. K. Ting

Abstract

This study is concerned with the breaking of irregular wave groups on a plane slope and the transformation of breaking waves through a laboratory surf zone. These wave groups were produced by random waves that are composed of a narrow range of wave frequencies. One irregular wave train was used in all of the experiments. Ten minutes of wave elevation data were taken by two resistance gages mounted on an instrument carriage that was positioned sequentially at 11 locations inside the surf zone. The wave measurements were synchronized with wave generation. The measured wave elevations were used to determine the wave height, wave period, wave length, and phase velocity for the individual waves. A wave-by-wave analysis was carried out on a representative wave group to study the variations of wave height and wave shape parameters in the surf zone. The results show that the wave-height-to-water-depth ratio approaches a constant value in the inner surf zone, while the wave length and wave period have wider variations inside the surf zone than outside the surf zone. It was found that low-frequency motion generated in the wave breaking process has a significant effect on the wave length, wave period and wave speed of the individual waves close to the shoreline. Individual waves were convected by the orbital velocities of the long waves. The resulting variation in wave speed from wave to wave produces changes in wave length and wave period. Statistical analyses were carried out on the entire wave record. The mean and standard deviation values of the wave shape parameters were compared with those from the chosen wave group. It was found that the mean and standard deviation values from the entire wave record generally do not represent the wave characteristics of the individual waves well, except in the inner surf zone. When the mean and standard deviation values were found from only the waves at breaking, those results compare well with the wave characteristics of the selected wave group. This study has provided new data into the breaking and decay of irregular wave groups in a laboratory surf zone. Further studies are needed for random waves with broad band of frequencies.

Library of Congress Subject Headings

Waves -- Analysis.
Water waves -- Analysis.

Publisher

South Dakota State University

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Rights Statement

In Copyright