Hydrodynamics of an oscillating water column WEC - breakwater integrated system with a pitching front-wall

Abstract To improve the adaptability in variable wave conditions, a novel oscillating water column (OWC) wave energy converter (WEC)-bottom mounted breakwater integrated system is proposed, in which the front-wall constrained by a torsional spring can oscillate in the pitch mode. In this study, an analytical model based on the eigenfunction matching method and technique of variables separation is developed to investigate the hydrodynamic performance (including energy conversion and structural safety) of the proposed integrated system. Taking the air compressibility and linear Power Take-off (PTO) system into account, the effects of the front-wall width, draft and spring stiffness on the performance are discussed, respectively. It shows that the interaction between the pitch motion of the front-wall and the air-pressure oscillation significantly broaden the frequency bandwidth of energy conversion efficiency (i.e., capture width ratio, Cw), in comparison with the traditional OWC device with the fixed front-wall. It is also found that those frequency points corresponding to the peaks of Cw satisfy the condition that the real part of complex air volume flux which is induced by unit air-pressure oscillation inside the chamber, is equal to zero, after decoupling and eliminating the influence of front-wall motion.