ENHANCING WAVE ENERGY EXTRACTION THROUGH BUOY GEOMETRY OPTIMIZATION: COMPARATIVE ANALYSIS AND EXPERIMENTAL VALIDATION OF A CYLINDRICAL–SPHERICAL POINT ABSORBER

Abstract

The commercial viability of point absorber wave energy converters (PA-WECs) remains constrained by the strong sensitivity of energy capture to floater geometry, yet direct comparative assessments of dissimilar buoy shapes under a unified numerical framework are scarce in the literature. This study presents a combined computational fluid dynamics (CFD) and frequency-domain hydrodynamic investigation of three candidate point absorber geometries a multi-section optimized buoy, a top-shaped buoy, and a cylindrical–spherical buoy   developed in SolidWorks and evaluated under identical regular wave conditions. Volume-of-fluid (VOF) simulations with the SST k–ω closure were performed in ANSYS Fluent to characterize near-field velocity and pressure loading, while boundary element method (BEM) computations in ANSYS AQWA quantified added mass, radiation damping, wave excitation, response amplitude operator (RAO), and heave response. The CFD results revealed nearly indistinguishable flow fields (peak velocities of 1.65–1.69 m/s; peak pressures of 14.65–14.69 kPa), demonstrating that near-field loading alone cannot discriminate geometric performance. In contrast, the frequency-domain analysis exposed pronounced differences: the cylindrical–spherical buoy achieved the highest added mass (2.31 kg at 7.62 rad/s) and radiation damping (17.57 N/(m/s) at 11.72 rad/s)   4.9 and 6.5 times those of the top-shaped buoy, respectively together with the largest displaced volume (2.78 × 10⁻³ m³). Although the multi-section buoy produced the largest heave RAO (5.66 m/m at 6.08 rad/s), the superior radiative coupling of the cylindrical–spherical buoy yielded the greatest power absorption capacity, with a theoretical mechanical absorption of 6.40 W and electrical output of 5.12 W at a wave amplitude of 0.025 m and frequency of 7.854 rad/s. A 0.574-scale prototype integrating a rack-and-pinion power take-off (PTO) and a DC generator was fabricated and tested in a 914 × 457 × 610 mm acrylic wave flume, generating peak voltages up to 1.50 V. Froude-type scaling (P ∝ λ³⋅⁵) reconciled the measured output with the numerical predictions, confirming that the discrepancy between the full-model estimate and the prototype response is dominated by geometric scale rather than modeling error. The results establish that maximizing radiative coupling and displaced volume rather than raw motion amplitude governs PTO-based energy extraction and identify the cylindrical–spherical buoy as the optimal configuration for small-scale wave energy harvesting applications