Hydrodynamic analysis of a spar-buoy wind turbine using computational fluid dynamics for design optimization

Abstract

The present work investigates the hydrodynamic behaviour of a spar-buoy floating platform, widely adopted for deep-water applications due to its enhanced stability, through numerical simulations performed with the open-source Computational Fluid Dynamics (CFD) toolbox OpenFOAM ^® . The study focuses on the influence of the platform’s inertial properties on its dynamic response, considering different mass distribution layouts obtained by varying the position of the centre of mass. Both operational and extreme sea states were analysed using mesh morphing and overset strategies to reproduce rigid-body motion while adapting the computational domain. The response of the floating system was assessed in terms of six-degree-of-freedom motions, mooring loads and line tensions. The results indicate that changes in the centre of mass position have a marked influence on platform dynamics and a more limited effect on load distribution within the mooring system. To investigate more severe wave loading conditions, where mesh morphing may be limited by excessive grid distortion, additional extreme sea state simulations based on an overset mesh approach were considered. The comparison between the two numerical strategies provides insight into the suitability of each method for different motion ranges. Overall, the study highlights the importance of accurately defining inertial properties and mass distribution of spar-buoy platforms during design.