Analysis of Bragg reflection phenomenon induced by an array of submerged twin-wing breakwaters

The interaction of gravity waves with an array of submerged twin-wing breakwaters (STWBs) is investigated based on the assumption of the linear water wave theory. A numerical solution utilizing the boundary element method is employed to solve the boundary value problem. In this study, we considered three types of twin-wing breakwater shapes, such as convex, inclined, and concave, to improve the effectiveness of wave attenuation. The proposed method is validated by comparing its numerical results with experimental and analytical findings from the literature, demonstrating its efficiency. The characteristics of Bragg reflection, including the conditions for its occurrence 2d/λ≈m (where λ is the wavelength of the incident wave, m is an integer, and d is the distance between the centers of any two contiguous breakwaters), the primary reflection peak, the phase downshift, and zero reflections are thoroughly discussed under various influencing factors, including length, draft, and array size in three STWB configurations. This analysis contributes to the efficient design of Bragg breakwaters, facilitating the creation of a tranquil wave environment in harbor areas. Furthermore, the Taguchi optimization technique is employed to optimize the response variable (i.e., the reflection coefficient) with respect to the influencing parameters.