An investigation of the hydrodynamic characteristics of an oscillating water column device using a level set immersed boundary model

In traditional renewable energy device design, physical experiments and potential flow solvers are commonly used to investigate hydrodynamic characteristics of wave energy converters. However, most potential flow models cannot deal with extreme free surface problems including wave breaking or splashing over the structure and scaling issues for physical experiments are very complex. Furthermore, for an oscillating water column device (OWC), the combined air and water motions influence the physical response of the device and cannot be properly represented without simulating both the air and water phases. Therefore a numerical method based on a two-phase level set with the global mass correction (Zhang et al., 2009) and immersed boundary method (Zhang et al., 2010) is developed to simulate wave interaction with a semi-submerged chamber. This method is initially employed to generate the 2D regular incident wave and compared with the theory. A shore-based oscillating water column, where power is extracted due to a normally incident wave forcing the free surface of the fluid between the front wall and rear wall to oscillate, is studied numerically to examine its hydrodynamic characteristics. The numerical results for an OWC under various wave periods are compared and validated with published experimental data (Liu, 2008). The effect on the efficiency of wave energy extraction from the OWC of wave period, immersion depth of the front wall and width of the chamber are investigated. Then, focused wave group is used to generate an extreme wave event. Focused wave results are compared with physical, experiments and numerical results. A test case involving an OWC under an extreme wave condition is also presented.