All of the project’s activities were centred around a novel mathematical framework for the computation of nonlinear Froude-Krylov forces, particularly useful when applied to wave energy converters. Main objectives involved the validation of the methodology via comparison with data gathered during experimental campaigns, the expansion of the methodology to a wider class of floaters (starting form axisymmetric and expanding to prismatic), and the computational burden reduction. The first activities were focused on the Sparbuoy floating oscillating water column, invented at Instituto Superior Tecnico de Lisboa, Portugal, also the secondment institution of the project. The novel mathematical model was implemented, after adaptation to match the Sparbuoy characteristics, also including case-specific description of the water column, air turbine and mooring system (modelled both in quasi-static in-house code, Moordyn, and Orcaflex). As a main result, the code was validated thanks to good comparison with experimental data; in particular, the code was shown able to detect and correctly articulate parametric resonance, which is a highly-nonlinear phenomenon, unperceived by conventional linear models, decreasing power extraction and potentially threatening survivability. A second major activity performed during the project focused on expanding the range of applicability of the proposed modelling approach, namely from only axisymmetric (widely used, but not covering the totality of wave energy converters) to also prismatic floaters. As major application case, the Inertial Sea Wave Energy Converter (ISWEC) device was considered, invented at the Marine Offshore Renewable Energy Lab of Politecnico di Torino, Italy, which was the host institution. After successful comparison with experimental data and existing state of the art codes, the influence of nonlinearity on the device performance was investigated, focusing on the interplay between model accuracy and energy-maximising control strategies. Furthermore, devices realizing direct and indirect extraction from hydrodynamically-excited modes were critically compared. Finally, the computational effort was reduced by optimizing the numerical integration algorithms and switching to object-oriented programming, resulting in a computational speed-up of at least two order of magnitudes with respect to versions prior to this project, in line with objectives. Finally, such results were disseminated within the scientific community by means of peer-reviewed journal papers and conference papers and, most importantly, an open source toolbox for the seamless implementation of the proposed novel method.
