Three-dimensional hydrodynamic analysis and efficiency optimization of submerged multi-cylindrical oscillating wave surge converter

摘要

The intense surge motion, the low installation costs and the less environmental threat, promote the development of the nearshore wave energy technologies which are often classified as Oscillating wave surge converters (OWSCs). This paper investigates the hydrodynamic performance of a multi-cylindrical fully submerged OWSC by developing a 3-D numerical model based on fully nonlinear potential flow theory and time-domain higher-order element method (HOBEM). A local change in the geometric configuration is verified as an effective approach to enhance wave energy extraction in long waves. Then, it is found that a larger incident wave height not only reduces the peak value of the capture efficiency, but it also leads to a change in the real resonant frequency. The geometrical parameters have a significant influence on the energy extraction, with the thicker, wider and shallower device demonstrating both higher average generated power and capture efficiency in low-frequency region. Meanwhile, the maximum efficiency is mainly related to the optimal PTO parameters. A two-value optimization strategy on PTO damping is applied to industriously maximize the absorbed energy over whole wave frequency region, and is easier to be implemented in practical application compared with ideal optimal scheme at each frequency component of incident wave spectrum.