WCSPH simulation of the forced response of an attenuator oscillating water column wave energy converter

In this study, a weakly compressible smoothed particle hydrodynamics (WCSPH) model was used to simulate the forced piston motion of water inside a fixed oscillating water column (OWC) wave energy converter. The considered device was a chamber with a complex entrance geometry attached to the rear wall of the wave flume. The effect of an impulse turbine on the chamber was modeled by an equivalent orifice damping force applied on a thin plate. This way, a balance is established between numerical accuracy and efficiency. The simulations were performed for two different wave steepness values of 0.025 and 0.04. To validate the model results, the experimental work performed in the wave tank at the Technical University of Denmark on this device was used. Fourier Transform analysis was performed on the SPH model results and experimental data to obtain the first-harmonic amplitude of the desired parameters. In general, a good correspondence was found between the SPH calculations and the experimental results for the piston motion of the water inside the chamber. However, the SPH results were slightly larger, especially around the resonance period. A possible reason is the placing of the plate above the free surface which might reduce the small sloshing motions of water inside the chamber. Finally, from the heaving velocity of the plate, the flux and pressure drop through the orifice were evaluated. It is shown that all three parameters reach their maximum around the resonance period of the chamber.