Improving floating platform performance as energy harvester and breakwater with local resonators

Floating hydroelastic platforms are increasingly used as lightweight, flexible structures for wave-energy harvesting and as floating breakwaters, for example, to protect offshore windfarms. Their effectiveness at low frequencies, however, is fundamentally constrained by practical limits on platform size. Motivated by recent progress in elastic metamaterials, this work explores whether attaching locally resonant devices to such platforms can extend their operational bandwidth. The core idea is to leverage sub-wavelength local resonance to improve wave attenuation and energy capture, particularly at frequencies below the platform’s first elastic mode. The study employs a unified finite element framework for floating beams and membranes, combining a 2D structural model with 3D potential-flow hydrodynamics. This produces a mixed-dimensional frequency-domain formulation in which each resonator is represented as a lumped mass–spring–damper. A wet-modal analysis is performed to quantify how the resonators modify the system’s natural frequencies, added mass, and wave–structure interaction characteristics, including reflection, transmission, and absorption. In the absence of resonators, classical results show that a 1D platform in a 2D fluid domain transmits nearly all wave energy at its elastic natural frequencies. Introducing a single local resonator fundamentally alters this behaviour: the platform exhibits almost complete wave reflection near the resonator’s natural frequency. The strength and location of this effect depend sensitively on where the resonator is placed and on its tuning. Including damping in the resonator leads to pronounced absorption peaks. Overall, the results demonstrate that local resonators enhance the low-frequency performance of floating hydroelastic platforms while preserving their inherent dynamic characteristics.