Wave power absorption and wave loads characteristics of an annular oscillating water column (OWC) wave energy converter (WEC) with an attached reflector

Numerous wave energy converters (WECs) have been developed, with the oscillating water column (OWC) device garnering significant attention due to its uncomplicated design, minimal active mechanical components, robust durability, and high dependability. The synergy between offshore wind energy and wave energy presents an opportunity for their combined and coordinated utilization. This study focuses on the integration of an OWC WEC into a monopile foundation of an offshore wind turbine. The OWC features an annular cross-section with a reflector attached at the base of the air chamber. The aerodynamic and hydrodynamic coupling problem of the above integrated system is solved using the high-order boundary element method (HOBEM), with the quasi-singular integral issue arising from the thin-walled structure addressed through the adaptive Gaussian integral method. Through a systematic investigation utilizing the developed numerical model, the impact of the geometric parameters and cross-sectional shape of the reflector on wave energy capture and wave-induced loads is analyzed, considering vertical, inclined and arc-shaped reflector configurations. Findings indicate that the attached reflector not only enhances the wave energy capture in short waves but also broadens the effective frequency range for wave energy capture. Furthermore, the study reveals instances where the wave loads on the OWC device and monopile foundation can counterbalance each other at specific frequencies, resulting in the nullification of wave loads on the system. Adjusting the reflector size enables the manipulation of the frequencies at which wave loads reaches the minimum.