CCP-WSI Blind Test Series 2 A Nonlinear Froude-Krylov Modelling Approach

The accuracy of mathematical models strongly influences the design and effectiveness of wave energy converters, and hence the ability to achieve economic viability and industrial feasibility. Despite the fact that the wave energy field is at least 45 years old, there is still a clear lack of standardization of modelling techniques, and a need for increasing confidence in hydrodynamic models. The Collaborative Computational Project in Wave Structure Interaction (CCP-WSI) aims to define a level playing field of comparison for a plurality of models, evaluating their performance using clearly pre-defined metrics. This paper implements a computationally convenient approach to represent nonlinear Froude-Krylov forces, along with the inclusion of nonlinear kinematics. The objective is to define a medium-high fidelity model that is able to compute at a fraction of the computational time typically required by fully-nonlinear models. Three focused waves are used as a case study, representative of highly-nonlinear sea states, hence particularly challenging to be modelled using partially-nonlinear potential theory-based mathematical models. Details and a critical discussion about the implementation are provided. A small computational time is obtained (between 4 and 13 times the simulation time). Results show major nonlinear effects, such as drift and nonlinear coupling between different degrees of freedom.