Theoretical analysis on hydrodynamic performance for a dual-chamber oscillating water column device with a pitching front lip-wall

Abstract

For the sake of extracting wave energy over a broader range of wave frequencies, dual-chamber OWC devices are more beneficial than the single-chamber one. In this paper, the concept of a dual-chamber OWC device with a pitching front lip-wall is proposed and by utilizing the matched eigenfunction method along the adjacent interfaces, present theoretical model developed under the framework of potential flow theory can be numerically solved. To determine the optimal turbine parameters combination of front and rear chamber for the optimal wave power extraction efficiency, a numerical method of successive approximation is employed. Parameters, including lip-wall drafts, installed location of mid lip-wall and angle spring stiffness are changed to explore effects on the hydrodynamic performance. It is found that when the device is designed with an asymmetry structure configuration, i.e., narrow front but wide rear, is more desirable and the optimal breadth ratio is 3:7. There exists a medium lip-wall draft condition which can satisfy stable operation and efficient performance simultaneously by including the pitching motion of front lip-wall. In addition, a relatively smaller spring stiffness (within the range of 105) is more recommended as the pitching motion of lip-wall can be adequately utilized to obtain a more satisfactory energy efficiency curve.