Abstract
The WEC-Sim is an open-source simulation tool for wave energy converters (WECs), developed in MATLAB/Simulink using the multi-body dynamics solver SimMechanics. This tool has been utilised to model both floating and submerged oscillating body WECs, as well as power take-off (PTO) and mooring systems. The paper describes the mathematical modelling implemented in a novel Simulink toolbox that enables the analysis of oscillating-water-column (OWC) WECs using the WEC-Sim tool. The new WEC-Sim Simulink OWC model addresses the mass balance of the OWC system by considering the thermodynamics of the air within the pneumatic chamber, the flow through both linear and non-linear turbines, and the use of safety valves arranged either in series or parallel with the turbine. It also incorporates the electrical generator and the control system for the PTO. An OWC device integrated into a breakwater was chosen as the test case to compare the results from WEC-Sim with those from an in-house frequency-domain numerical model based on linear potential flow theory. This comparison aims to assess the accuracy of the mathematical model and demonstrate the capabilities of the numerical method. Results indicate that the WEC-Sim tool can be easily adapted to accurately compute the dynamics of OWC-type WECs, taking into account air compressibility in the pneumatic chamber, linear and non-linear turbines, air valves in both series and parallel configurations with the turbine, electrical generators, and the control of the turbine-generator setup, under various sea states, whether high or low energy.