Motion-resonant modes of large articulated damped oscillators in waves

Using a semi-analytical approach, we show that an articulated system of large damped oscillators in the open ocean can be resonated by incoming waves at multiple frequencies. As an application, energy extraction from the system is modelled when the oscillators are used as flap-type wave energy converters. A new parameter – the absorption efficiency – is introduced to analyse the performance of the system at resonance. This allows us to identify the occurrence of detrimental processes near the resonant frequencies, which reduce the sustainability of the energy conversion process. This result challenges the diffused belief that large flap-type wave energy converters must be designed to resonate, which is based on the use of inappropriate performance descriptors.