Wave power extraction analysis on a dual-chamber oscillating water column device composed by two separated units: An analytical study

The hydrodynamic characteristics of a dual-chamber oscillating water column device system with a gap between each unit is considered in this paper. A theoretical model is established to explore its wave power extraction performance under the framework of linear water wave theory and matched eigenfunction technique. A numerical strategy of successive approximation is utilized to seek for the optimal turbines combinations for the optimal energy absorption efficiency. Effects of the total chamber breadth, lip-wall drafts, breadth ratio for front and rear unit and gap length on the wave power extraction efficiency are explored and analysed. It is found that a larger total chamber breadth is more beneficial for the wave power extraction both for short and long wave regimes, and when the front and rear unit breadth ratio is 2/3, a more desired efficiency distribution could be obtained. Though the increase of lip-wall drafts (except for the most front one) could lead to a more satisfactory peak efficiency value and a much broader effective frequency bandwidth, the superiority of present system lies in the condition with relatively smaller lip-wall drafts in contrast to the single-chamber one. In addition, the gap length can effectively contribute to the formation of multiple peak efficiency values at the short wave regimes, especially under the condition that with a large gap length and significant improvement of efficiency could be achieved within a specified range of wave frequencies.