Extreme loading on a fixed OWC wave energy converter: Experimental insights into survivability under focused wave conditions

To ensure the long-term reliability and cost-effectiveness of wave energy extraction, assessing the structural survivability of devices in harsh environments is critical. This study experimentally investigates the extreme loading characteristics of an OWC device subjected to focused waves. The pneumatic pressure inside the air chamber, the hydrodynamic pressure acting on the OWC device, and the total horizontal wave force exerted on the structure were evaluated. The evolution of these parameters was systematically analyzed under varying focused wave amplitudes and spectral characteristics. Results indicate that the magnitude of the peak positive pneumatic pressure is notably smaller than that of the corresponding negative pressure trough, revealing that the negative pressure generated by the falling water column exceeds the positive pressure induced by the rising water column. This suggests that resistance to suction loading is a critical factor in structural design. Furthermore, as wave amplitude increases, the hydrodynamic pressure curves exhibit distinct high-frequency oscillations, attributed to the high-frequency fluctuations of the water surface within the chamber induced by the intensified fluid-structure interaction. Notably, when the wave amplitude-to-draft ratio exceeds 0.3, the maximum pneumatic pressure exceeds the hydrodynamic pressure, highlighting the increasing importance of pneumatic loading in the survivability assessment of OWC devices under extreme wave conditions. Similarly, the horizontal wave force displays oscillatory behavior at high incident wave amplitudes. Although these oscillations have a limited influence on the peak force magnitude, the sustained high force levels may pose a risk to the structural stability of the device. These findings provide useful insights into structural design and safety considerations for OWC systems under extreme wave conditions, thereby contributing to the development and commercial viability of OWC technology.