Comprehensive Stability Assessment Approach of Floating Offshore Wind Turbines for Multi-Directional Evaluation

The rapid development of offshore wind energy has resulted in the saturation of suitable sites for fixed offshore wind turbines in shallow waters, necessitating the adoption of floating offshore wind turbines (FOWTs) for deeper locations. To ensure the safety of FOWTs in the event of the complete failure of all the moorings, this study investigates the stability of FOWTs without considering the restoring effects from the moorings. However, existing commercial software is unable to identify the angle at which the FOWTs exhibit the worst stability under different external wind force directions. Additionally, it cannot determine the critical wind speed considering the operational condition of FOWTs. Moreover, commercial software tends to be inflexible, and its computational methods lack transparency. To overcome these issues, this study establishes an analytical procedure and a self-developed program that requires only Stereolithography (STL) for a 3D model and predefined parameters, thereby overcoming the limitations of modeling numerical models in specific commercial software. The critical wind speed is determined by the operational thrust force of the FOWT and the wind pressure acting on it, using an optimization theorem. For the numerical case study, the IEA 15[Formula: see text]MW FOWT is used to evaluate its hydrostatic stability. The righting moment across multiple direction is analyzed, identifying geometric characteristics through contour plots. Additionally, the critical wind heeling moments in multiple directions are determined using an optimization theorem, with a clear focus on external forces that pose the highest risk. Finally, the performance index in multi-directional evaluation is proposed to enhance FOWT hydrostatic stability assessment by identifying critical angles and guiding targeted structural improvements.