Inaug.-diss.--Rostock.

Inaug.-diss.--Rostock.

This thesis describes the design of a proposed, new hydraulic laboratory, wave generator for use in a 39'-4¼'' long, 30" wide and 36" deep flume, and the re-design of a small wave generator previously built for a 21'-3 5/8" long, 8 3/4" wide and 10 5/8" deep flume. These relatively short flumes are installed in the Hydraulics Laboratory of the Department of Civil Engineering, University of British Columbia, and the installation of the proposed, new wave generator would augment the present limited wave research facilities. The project is supported by an operating grant from the National Research Council of Canada. The preparatory study of laboratory wave generators in use, presented herein, was made to determine how they function and their design problems. It was concluded that a rigid paddle, double articulation type would be best for generating deep-water, transition and shallow-water waves in a flume of relatively short length. Biesel's wave generator theory is outlined and was used in estimating wave heights and in determining power and strength requirements. The existing wave generator for the "small" flume is a rigid paddle, double articulation type. It did not function satisfactorily due to a very irregular paddle motion. The causes were isolated and a new drive system designed and installed, with good results. The resulting new operating specifications are: power = 1. Hp (D.C.) wave period range = 0.34 to 2.1 sees. design water depth = 6.5" estimated maximum wave height = 4" The proposed, new wave generator for the "large" flume is a rigid paddle, double articulation type designed around the adjustable paddle concept of G.D. Ransford (1949) as modified by Lt. CB. Coyer (1953). The designed operating characteristics are: power = 10-Hp (D.C.) wave period range = 0.68 to 4.28 secs. design water depth = 25" estimated maximum wave height = 14" / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

In the first part of this thesis, the nonlinear Schrodinger equation for inviscid cross-waves near onset is found to be modified by viscous linear damping and detuning. The accompanying boundary condition at the wavemaker is also modified by damping from the wavemaker meniscus. The relative contributions of the free-surface, sidewalls, bottom, and wavemaker viscous boundary layers are computed. It is shown that viscous dissipation due to the wavemaker meniscus breaks the symmetry of the neutral curve. In the second part, existence and stability of steady solutions to the nonlinear Schrodinger equation are examined numerically. It is found that at forcing frequency above a critical value, f(c), only one solution exists. However, below f(c), multiple steady solutions, the number of which is determined, are possible. This multiplicity leads to hysteresis for f < f(c), in agreement with observation. A Hopf bifurcation of the steady solutions is found. This bifurcation is compared with the transition from unmodulated to periodically modulated cross-waves observed experimentally.

by Ng Chi Shing. / Chinese title in romanization: Shao sheng bo zai deng li zi ti guan dao nei di fei fa san zhuan bo. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1987. / Bibliography: leaf 70.

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