Feasibility study of potential flow and viscous flow models for a bistable wave energy converter using numerical and experimental methods

Bistable mechanisms (BMs), which have the potential to improve the capture efficiency and broaden the frequency bandwidth, have recently been explored for use in wave energy converters (WECs). Currently, most research is conducted using simple models that ignore fluid viscosity. In this study, a numerical viscous flow model for the classical BM-WEC is developed, along with a corresponding simplified potential flow theoretical model, to provide a comprehensive comparative study of potential flow and viscous flow models for bistable WECs. As a benchmark, a physical model of the BM-WEC was constructed for testing in a wave flume. The comparative study shows that nonlinear damping predominantly influences the predictive results of the BM-WEC. The evolving trend of results with varying damping is revealed, demonstrating that the potential flow model can perform well if the precise nonlinear damping can be determined. With the introduction of the BM, the energy capture efficiency at lower frequencies and wave attenuation performance at higher frequencies have significantly improved. The concept of the nonlinear numerical model proposed in this study may be extended to address other wave-structure nonlinear coupling problems.