Study on Power Capture Performance of the Edinburgh Duck Wave Energy Converter Based on a CFD Model

The Edinburgh Duck Wave Energy Converter (ED-WEC) is one of the most efficient wave energy converter. To predict the wave-structure interaction process and further the wave power capture performance of the ED-WEC, two most commonly used tools, i.e. the potential theory model and the Computational Fluid Dynamic (CFD) model, are two competitors and both require meshing of the Duck. Since the Duck is quite long, a direct meshing of the Duck is impossible because the mesh count will be high enough that beyond the capacity of the software. Meanwhile, the large length of the Duck permits reducing the three-dimensional wave-structure interaction problem to a two-dimensional problem, which rules out the potential theory model since most potential theory based software naturally define the velocity potential in three-dimensional space. As a result, the CFD model is employed in this paper to solve the two-dimensional wave-structure interaction problem of the ED-WEC, and the results are compared with the potential theory model concerning a short Duck. It is found that the numerical wave tunnel established in the CFD model is able to generate waves with high quality. The difference of the hydrodynamic response predicted from the CFD model and the potential theory model is small at low wave amplitudes but grows significantly at high wave amplitudes, suggesting that the wave-structure interaction for a Duck with infinite length is slightly different from a short Duck and the CFD model is able to capture nonlinearities within the wave-structure interaction process. Based on the CFD model, the high wave power capture efficiency of the ED-WEC is visually demonstrated by an overlaying image consisting of five water-phase snapshots.