Finite-Order hydrodynamic Approximation by Moment Matching (FOAMM) toolbox for wave energy applications

Cummins’ equation is commonly used to describe the motion of Wave Energy Converters (WECs), where the radiation force is characterised by a convolution operation. The computational effort associated with the solution of the convolution term, often represents a drawback for e.g. optimisation or exhaustive-search studies. To overcome this disadvantage, and given that the convolution operator intrinsically defines a dynamical system, the convolution term is commonly approximated using suitable finite-order parametric models. To this end, the Centre for Ocean Energy Research has recently presented a moment-matching based identification method for the radiation force subsystem and the complete force-to-motion WEC dynamics (i.e. wave excitation force to device velocity). Motivated by the theory and the obtained results, already reported by the authors, the FOAMM MATLAB application has been developed, which systematically implements the moment-matching based identification strategy from raw frequency-domain data, provided by hydrodynamic solvers, in a user-friendly fashion. The aim of this paper is to describe the theoretical background behind the identification strategy, and the structure, organisation and characteristics of the developed application. Additionally, the relevant modes of operation, along with the different options of the toolbox are explained, and, at the end, a step-by-step example of how to use the FOAMM application is provided, along with recommendations from the authors.