A Hybrid CFD and Potential Flow Motion Analysis of Spar Buoys with Damping-Enhanced Appendages

Abstract

This study investigates the hydrodynamic response of a spar-type buoy equipped with a solid, perforated, and novel corrugated plate appendage introduced here for the first time to enhance motion damping. A hybrid approach combining time-domain CFD simulations and frequency-domain potential-flow analysis was employed, providing a framework to incorporate viscous effects that are often omitted in potential-flow models. In the first stage, free-decay simulations were carried out in ANSYS Fluent for a baseline spar and three appendage-equipped configurations. The resulting heave and pitch decay responses were analyzed to determine natural frequencies and viscous damping coefficients. Prior to that, the CFD solver was validated and verified against published experimental data, confirming the reliability of the numerical setup. In the second stage, frequency-domain hydrodynamic diffraction analysis was conducted in ANSYS AQWA, and the CFD-derived viscous damping coefficients were incorporated into the potential-flow model to improve motion predictions near resonance. The comparison between RAOs with and without viscous damping indicated reductions of approximately 55–62% in heave and 41–60% in pitch at resonance, with the perforated plate consistently yielding the highest damping and lowest RAO peaks. This work introduces the first corrugated plate appendage design for spar buoys and establishes a validated CFD–potential-flow hybrid framework that enables more realistic motion predictions and provides practical design guidance for damping-enhanced spar buoys in offshore energy applications.