Data-based hydrodynamic modelling of a fixed OWC wave energy converter

MARCO ROSATI; TOM KELLY; DEMIÁN GARCÍA VIOLINI; JOHN RINGWOOD

Plymouth

Conferencia; 14th European Wave and Tidal Energy Conference (EWTEC); 2021

Plymouth University

System identification (SI) techniques represent an alternative strategy to provide the hydrodynamic model of oscillating water column (OWC) devices, compared to relatively laborious, and potentially inaccurate, model determination from first principles. In particular, the assumption of small variations about equilibrium of the water column, combined with difficulties in calculating added mass, make the linear boundary-element modelling of OWCs particularly challenging. With SI, the parameters of the model are obtained, by minimizing a cost function, from input-output data. Even though OWC modelling typically features physics-based methods, such as linear potential theory or computational fluid dynamics (CFD), SI has already been successfully employed in the modelling of other wave energy devices. The main advantage of SI is its simplicity, as well as its potential validity range, where the dynamic model is valid over the range for which the identification data was recorded. This work aims to develop a data-based hydrodynamic model of a single chamber OWC wave energy converter by employing system identification. Real wave tank (RWT) data of a scaled model are gathered from the narrow tank experimental facility at Dundalk Institute of Technology (DkIT). Particular attention is paid to the selection of suitable input signals for the experimental campaign, in order to ensure that the model is subjected to the entire range of equivalent frequencies, and amplitudes, over which model validity is required.