Hydrodynamic loading analysis of an oscillating water column wave energy converter coupled with a land-fixed parabolic breakwater

• Wave loads on an OWC integrated into a parabolic breakwater was investigated. • A second-order time-domain OWC-breakwater HOBEM model was developed. • The peak wave forces are over three times that of the isolated device. • Actual focal position shows a great influence on the wave forces. The multi-functional integration of a parabolic breakwater and a Wave Energy Converter (WEC) can potentially focus wave energy and significantly enhance wave energy capture. However, the WEC is also subjected to the converging concentric wave interaction. The hydrodynamic loads associated with survivability are a critical concern that requires thorough investigation and improvement. This study focuses on the wave forces on an Oscillating Water Column (OWC) WEC coupled with a parabolic breakwater. Based on the time domain potential flow theory, a 2nd-order boundary element method was established to simulate the wave action with the multi-functional integrated system. Two carefully instrumented experiments analyzing the coupled parabolic breakwater and OWC device were developed to validate the numerical model. After that, the validated model is used to predict the nonlinear wave forces applied to the OWC by considering the effects of the environmental conditions and the geometric parameters. It is found that the resonant wave forces on the integrated system exceed three times the wave forces applied to an isolated device. The resonant frequencies of the surge and heave forces alternate at quarter-wavelength intervals. The 2nd-order wave force plays a significant role, even surpassing the contribution of the 1st-order waves in certain wave conditions. The pressure distributions on the OWC chamber wall are discussed, and the maximum pressure amplitude is located at the rear wall and near the still water level. The actual focal position associated with incident wavelength and direction notably influences the wave forces applied to the OWC device.