Numerical investigation of diffraction and radiation of surface gravity waves by a rectangular structure over a stepped bottom with and without a vertical wall

A numerical investigation based on the boundary element method is conducted to analyze the effect of step bottom on the radiation of surface gravity wave by the rectangular marine structure under the assumption of a two-dimensional linearized water wave theory. The investigation is supplemented by analyzing the presence of a back wall located near the floating structure. The accuracy of the method is validated using the known special case of published results. Hydrodynamic coefficients such as added mass and damping coefficients and wave excitation force coefficients are evaluated in both cases. The influence of depth ratio and the distance of step from the center of the structure is calculated to understand the role of the stepped bottom on the hydrodynamic coefficients. On many occasions, these results are compared with the flat bottom case. The study results are helpful to understand the influence of the step-type bottom profile on the design of floating rectangular structures in various marine structure applications and wave energy converter devices.