Numerical Approach to Air-Gap Assessment of Overhanging Wind Turbine Blades on a WTIV Under Various Environmental Conditions

This study investigates the safety of overhanging wind turbine blades during transportation on a wind turbine installation vessel (WTIV) by analyzing the air-gap between the blade tip and the wave surface under various environmental conditions. Both hydrodynamic analysis, based on radiation–diffraction theory, and computational fluid dynamics (CFD) analysis, including viscous effects and a regular design wave approach, are conducted. Hydrodynamic analysis indicates that beam wave directions constitute the most critical conditions for air-gap, with resonance effects significantly reducing the safety margin. The resonance effect reduced the air-gap margin by approximately 52% and 51% in transportation and installation and extreme conditions, respectively. CFD analysis generally estimates more conservative air-gap values and indicates the generation of pressure on the submerged blade tip. A maximum difference of approximately 24% is observed between the CFD and hydrodynamic analyses. The findings highlight the necessity of carefully considering wave height and period relative to the WTIV’s motion characteristics to ensure safe operations and prevent blade submersion. This research establishes a valuable approach for evaluating air-gap and pressure on overhanging blades, highlighting the importance of appropriate selection of operating environmental conditions. Further study should focus on model tests and alternative arrangements to further validate these results.