Numerical Experiments On Transverse Oscillations In A Harbor With A Hyperbolic-cosine Squared Depth

In this thesis,a fully nonlinear Boussinesq numerical model FUNWAVE2.0 is used to simulate the transverse oscillation of the(1,0)mode and(1,1)mode in a harbor with a hyperbolic cosine water depth.Inspired by the study of edge waves,the transverse oscillation of the(1,0)mode is excited by the incident wave whose frequency is twice that of the transverse oscillation,which is called subharmonic transverse oscillation.By setting an initial disturbance on the surface,the transverse oscillations in the harbor were excited successfully only if the wave height of the incident wave exceeds a certain threshold.Even a small initial disturbance will grow exponentially to a significant transverse oscillation whose amplitude only depends on the shape of harbor and incident wave rather than the amplitude of initial disturbance.With the help of wavelet transform,the wave energy transfer and damping process of each frequency in the harbor is analyzed.In addition,the transverse oscillation of the(1,0)mode can also be excited by the incident waves with the same frequency and this is called synchronic transverse oscillation.In the cases where a slight cross-harbor bottom slope was added,the transverse oscillation can be excited.It is found that the cross-harbor bottom slope only responsible for the transverse perturbations and the growth of the transverse oscillation relay on the wave-wave nonlinear interaction.Compared with subharmonic oscillation,the growth pace of synchronic oscillation is faster and the amplitude is larger after approaching the steady state in the same harbor.In order to further evaluate the synchronic transverse oscillation of higher-order modes,the(1,1)mode synchronic transverse oscillation is analyzed.The effects of longitudinal slope,cross-harbor slopes and incident wave height on transverse oscillation are evaluated.It is found that the(1,1)mode transverse oscillation grows faster than the(1,0)mode,and more widely distributed in the harbor thus more harmful.