Performance evaluation of oscillating water column in the presence of variable sea bottom

The development of an oscillating water column (OWC) device under extreme wave conditions has been identified as the most successful and promising approach to harness the ocean wave energy. In most of the coastal regions, the sea bottom profiles are variable, and they play a pivotal role to enhance the performance of the OWC device. Thus, the present numerical study investigates the significance of the variable seabed profiles while analyzing the efficiency of an OWC device in various wave conditions. The physical problem is formulated in a two-dimensional Cartesian coordinate system within the framework of linearized potential flow theory. The dual boundary element method (DBEM) is employed to solve the boundary value problem (BVP). The numerical results are validated with the available experimental and numerical results. Various effects, such as the spacing between the variable seabed and lip-wall, chamber width, seabed classification, seabed elevation difference, lip-wall draft, and lip-wall rotation on the wave radiation and force coefficients, are presented against the relative wave frequency. The free spacing and chamber spacing play an evident role in developing resonanting peaks and troughs in the OWC efficiency curve. The time-domain simulations of the free surface elevations in the presence of variable seabed profiles and OWC device are provided by considering the incident wave as a Gaussian wave packet. The protrusion type-B seabed enhances the efficiency of the OWC device as compared to the other seabed profiles when chamber spacing is higher than the water depth.