Ocean wave transmission, reflection and absorption by rows of vertical structures along the coastline

Large arrays of wave-absorbing structures could serve the double objective of coastal protection against erosion and clean, renewable electrical power production. In this work, the principle of an artificial canopy is explored, which consists of vertical structures, arranged in rows parallel to the coastline. Sea waves, which propagate towards the shore, interact with the obstacle rows. A part of the wave energy is reflected back towards the ocean, another part is transmitted to the shoreline, while the rest of the energy is, in theory, available for energy production (although losses, due to viscous effects within the fluid, or imperfect efficiency of the power conversion mechanism, will unavoidably take place). First, a simple geometric representation of the reflection/transmission properties of individual, fixed rows is presented. In the case of moving rows, relationships are drawn between the internal stiffness and damping parameters of the devices, on the one hand, and their reflection, transmission and absorption characteristics, on the other hand. Array properties are then examined, depending on both individual row design parameters and row-to-row spacing values, using the widespacing approximation. A numerical case study illustrates the capabilities of the proposed modelling framework, with arrays of vertical, oscillating rectangular plates. The transmitted, reflected and absorbed wave spectra are examined, along with their dependencies on individual oscillator control tuning and array design parameters.