The Oscillating Water Column (OWC) device is recognized as one of the most promising Wave Energy Converters (WECs) for its structural simplicity and high efficiency. The reliability of the OWC WEC plays an important role in the process of application and commercialization. The wave loads on an offshore cylindrical OWC device is considered in this paper. Based on the potential flow theory, a time domain Higher Order Boundary Element Method (HOBEM) model is developed to simulate the hydrodynamic loads and pressure on an offshore stationary OWC device. A quadratic pneumatic damping is introduced to simulate the effects of the Power Taken-Off (PTO). An experiment was carried out to validate the accuracy of the HOBEM model. A good agreement was observed between the numerical and experimental results for the hydrodynamic pressure and chamber surface elevation. The effects of the wave conditions and PTO damping on the wave dynamics of the OWC device are investigated. The PTO damping has a significant influence on the hydrodynamic pressure inside the OWC chamber. A second order wave resonance phenomenon was observed inside the OWC chamber. The surge force and the pitch moment are found to be insensitive to the variability of the orifice opening ratios.
Ocean energy has received worldwide attention to cope with the global warming and energy crisis (Ahamed et al., 2020). The ocean wave, which can travel over a long distance, serves as an important part of the ocean renewable energy resources. To harness the wave energy, various types of wave energy converters (WECs) have been designed and developed. Oscillating water column (OWC) is recognized as a promising WEC, which is made of a semi-submerged chamber (either fixed or freely floating) and a power take-off (PTO) system (Hayati et al., 2020). The water column oscillates and creates the reciprocating pneumatic flow inside the chamber, and a generator is forced to generate electricity. Up to now, a lot of OWC WECs have been studied and tested, including the full-scale prototype experiments (Falcão & Henriques, 2016). And some innovative solutions have been proposed and proved for the multi-functional application, such as the OWC WECs integrated into the fixed/floating breakwater (He et al., 2017) and wind turbine (Sarmiento et al., 2019). However, due to the low viability and conversion efficiency, the development of the OWC wave energy conversion technology needs a lot for reaching the commercialization.
