Nonlinear dynamic analysis of a 3D land-fixed oscillating water column wave energy converter

In the process of the wave energy exploitation, in addition to the energy conversion efficiency, the wave loads acting on oscillating water column (OWC) wave energy converters (WECs) should also be considered as a design factor. This paper investigated the dynamic characteristics of a three-dimensional (3D) fixed OWC-WEC through numerical methods, with validation based on physical model tests. The physical experiment was carried out in a wave tank at Dalian University of Technology. The second-order time-domain higher-order boundary element method (HOBEM) was adopted to simulate the nonlinear interaction between waves and OWC device. The numerical model was validated by the comparison with the experimental data. Then, the effects of the 3D diffraction and wave nonlinearity on the dynamic characteristics of the OWC device were studied. The results indicate that the wave diffraction causes significant changes in the hydrodynamic pressure distribution on the front-wall outer surface of the air chamber. The wave diffraction also causes the wave frequency corresponding to the minimum wave reflection factor (the ratio of the reflected wave height to the incident wave height) to deviate from the resonance frequency. On the other hand, the linear model underestimates the wave forces. This underestimation increases with increasing incident wave amplitude, especially in the high-frequency range.