||The purpose of this thesis is applying Lagrangian approach to analyze shoreward progressive waves over a gently sloping bottom. A series of laboratorial experiments were executed to validate the analytical results. Then, the theory is extended to the prediction of wave breaking and the resulting breaking criteria are shown to be more accurate than regression formula in the literature.|
In the analysis, a two-parameter perturbation were used that employs both bottom slope α and wave steepness ε , and the solution is expanded up to the order. Based on this analytical solution, water particle trajectory, waveform and wave velocity in the shoaling process are calculated and their counterparts in the laboratorial experiment are recorded for comparison. Then, the analytical solution is used to derive the wave height, the water depth, and the wave velocity for a breaking wave where the Kinematic Stability Parameter (K.S.P.) u/Cw equaling one is adopted as the breaking criteria.
In deriving the O( ε^3α^0) solution, the following conditions are satisfied at each order: (a) The pressure on the free surface is constant, and (b) the mass flux is conserved at each vertical cross section. This solution can accurately describe the waveform, the water particle trajectory and the wave velocity all the way from the deep water to the breaking point, as is shown by the comparison with the laboratorial experiments. The perturbation with respect to the bottom slope α is included and the flow at the bottom is consistent with the sloping bottom condition. Consequently, the present analytical solution can provide better breaking criteria than previous regression formula, especially in the case of large sloping angles.