The diffraction of nonlinear wave interacting with vertical offshore structure in shallow water over an uneven bottom is investigated. An extension of the open boundary condition developed by Lu (1989) is adopted so as to make the solution of time-dependent problem in semi-infinite spatial domain by numerical approach feasible. Contrary to the data shown in our previous work (1991), the computed results involving the wave force, wave run up for the present case exhibit significant differences than that for the case of wave diffraction in shallow water over a bottom of constant depth, where the effect of wave refraction due to topography does not occur. The order of magnification of wave force depends upon the topography and the relative location of the cylinder to the bottom bump as well. Some interest phenomena and inherent characteristics relevant to the problem In consideration are shown. A finite difference method based on the spatial discretization of triangular grids layout is used, to meet the goal of dealing readily with offshore structure of arbitrary cross-section.
As viewed from applications, to coastal and offshore engineering, wave-body Interaction in shallow water has been a subject of major concern. The surface wave theory reveals that only in the case where two parameters, i. e., the ratio of water depth versus wave length and the ratio of wave amplitude versus water depth, are small, the shallow water linear wave approximation is available. However, for many coastal and offshore problems, the second restriction is too severe and in general can not be satisfied, it is therefore essential to investigate those problems in virtue of nonlinear wave theory in shallow water. In this context, the theory is involved with three length scales and two parameters.
