Theoretical modelling of U-Oscillating Water Column energy harvesters integrated in floating platforms

This article develops a nonlinear dynamic model of a U-Oscillating Water Column (U-OWC) wave energy converter (WEC) embedded in a rigid floating structure. Specifically, it considers the implementation of the U-OWCs into floating multipurpose platforms, where they can be used for absorbing part of the incoming wave energy, thus protecting the system while enhancing its energy security in operative conditions. Currently, no mathematical model quantifying the response of a floating U-OWC is available. For filling this gap, this article proposes a model based on the unsteady Bernoulli equation. Compared to other floating OWC models, a notable advantage of this model is that real fluid flow phenomena critical to the U-OWC modelling are accounted for, as well. A critical feature of the proposed model is the inclusion of apparent forces required for capturing the effects of the floating body dynamics on the WEC response. The proposed theoretical model is validated against the experimental data obtained from the physical model test of the 1:40 scale model of the Blue Growth Farm multi-purpose floating platform. The article shows that the model captures the salient features of the U-OWC time-domain response. Moreover, it highlights its limitations associated with the assumption of piston-like dynamic behaviour.