Array resonances in periodic wave energy converter arrays

We study the hydrodynamics of ocean wave energy converter (WEC) arrays consisting of periodically repeated sub-arrays of heaving buoys. In particular, we focus on lattice-like array configurations and study the effects of periodicity and row spacing on array gain. We discuss two types of general array-configuration-related resonances that have not been discovered in WEC array context before. We first discuss the effects of Laue resonances -- a wave scattering phenomenon occurring when the phase difference between an incident wave and a scattered mode is the same for every body in the array. We present the analytic condition for the occurrence of Laue resonances (involving the incident wavenumber and the array configuration parameters) and match it to prominent decreases in array gain. Second, we discuss the presence of motion-trapped Rayleigh-Bloch (RB) waves -- homogeneous wave solutions to the governing equation that do not radiate to the far field, but stay trapped around a periodic array of oscillating bodies. Based on our numerical simulations, we present evidence that these RB waves exist for a special category of periodic arrays and that they can be excited by an incident wave. These resonances lead to large, narrow-banded increases in the array gain.