Parametric optimization of a twin-hull backward bent duct buoy wave energy converter via geometric tuning and hydrodynamic coupling

A twin-hull backward bent duct buoy (BBDB) wave energy converter provides an innovative solution for enhancing oscillating water column performance through hydrodynamic interaction and geometric tuning. A three-dimensional numerical model was developed and applied to a parametric study of horizontal duct length, buoyancy cabin length ratio, and duct spacing ratio under regular wave conditions. Hydrodynamic performance is quantified using capture width ratio and pneumatic power output, while motion response and flow-field diagnostics are used to reveal the mechanisms governing energy conversion efficiency. The results show that the horizontal duct length (l) governs resonance tuning, with a peak response at l = 32 m where capture width ratio exceeds 1.05. The horizontal duct spacing ratio (ds) is another key tuning parameter. For l = 32 m, the optimal spacing ratio is ds = 1.0, consistent with intensified gap flow and enhanced motion coupling. Compared with a single-hull BBDB converter, the twin-hull configuration increases peak capture width ratio from 0.92 to 1.28, leading to an improvement exceeding 39.5%, and extends the wave-period range with capture width ratio above 0.8 by more than 114.3%. Buoyancy cabin length ratio (lc) exerts a comparatively weak influence on capture performance, and lc = 0.5 provides a practical optimum that sustains strong capture efficiency across the primary operating band. These findings offer quantitative design guidance and elucidate the coupled hydrodynamic interaction mechanisms that drive performance enhancement in twin-hull BBDB converters.