Bragg scattering of surface gravity waves by a graded array of surface-piercing porous barriers of arbitrary configurations: A numerical approach

We implement porous breakwaters to mitigate the effects of wave loads on diverse marine structures and to dissipate excess wave energy, thereby establishing a tranquil zone. This paper demonstrates the effectiveness of wave scattering by a graded array of surface-piercing vertical porous barriers of different configurations, namely, (a) monotonically decreasing, (b) monotonically increasing, (c) convex, (d) concave, and (e) uniform patterns. The barriers are assumed to adhere to quadratic pressure boundary conditions to accurately model energy dissipation with variations in wave height, a factor often overlooked when using Darcy's law. A generalized technique using the dual boundary element method (DBEM) is devised to solve the boundary value problem efficiently. The accuracy of the present study is confirmed by comparing them with the results available for particular structural configurations. It can be seen that wave energy reflects less and dissipates more for respective cases of barrier configurations with moderate porosity and barrier spacing. The practical interest in this problem stems from the result that the configuration with a monotonically increasing pattern is found to be the best wave energy dissipative system among other configurations considered in the study. The frequency domain results are used to simulate the surface elevation in the time domain, using the Fourier transform to demonstrate the wave propagation in the presence of barriers. Significantly, the outcomes of this study are anticipated to be valuable for optimizing the designs of such wave barriers, and the results have implications for harnessing energy from ocean waves.