Numerical Verification of Externally Installed Devices Employing Inerter Mechanism for Vibration Mitigation and Energy Conversion of Offshore Floating Buoys

In recent years, ocean energy such as wind and waves has been attracting attention as promising renewable energy sources. Especially, offshore wind turbines (OWTs) show great potential, and various kinds of OWTs have been proposed so far. Among them, floating OWTs are considered more suitable for Japan due to the deep waters in the nearshore area. However, floating type is vulnerable to wind- and wave-induced vibration to compared to bottom-fixed OWTs. On the other hand, a wave energy converter (WEC) with an inerter mechanism consisting of a rotational mass was proposed. Thus, this study proposes novel externally installed devices employing inerters for vibration mitigation and wave energy conversion of floating OWTs. A simple analytical model including the effects of additional mass, radiation damping, and wave excitation force on the floating body is developed for the heave motion behavior of the proposed floating OWT. Then, appropriate design parameters are examined, and the vibration mitigation and power generation performance are investigated through numerical simulation studies to irregular waves generated by the JONSWAP spectrum using WEC-Sim (Wave Energy Converter SIMulator). The result shows that the proposed device works well to control the floating OWT and generate energy.