A systematic experimental investigation on the aerodynamic contribution to mooring tension response in floating offshore wind turbines

Quantifying the aerodynamic effects on mooring line tension is essential to distinguish wind-induced impacts from wave-driven dynamics and to improve the understanding of mooring system behaviour under coupled environmental loading conditions. The present work provides the first systematic experimental quantification of the aerodynamic contribution to mooring system response. An extensive wave tank campaign was conducted on a Froude-scaled Floating Offshore Wind Turbine under regular and irregular waves, both with and without wind, and for aligned and misaligned conditions. Although the experimental campaign focused on a single structural configuration, the results were analysed to identify response trends and governing physical mechanisms with a reasonable degree of transferability to other configurations. Results demonstrate that wind-induced thrust is the dominant driver of mooring system response, leading to a pronounced asymmetry in the distribution of line tensions, with load amplification in upwind lines and load reduction in downwind lines. Wind governs mean loads, whereas waves mainly control oscillatory behaviour, although aerodynamic effects remain relevant for peak responses under severe sea states. Wind thrust is the main cause of the non-linear response of mooring lines, which can be exacerbated by irregularities in wave motion and by misalignment between wave and wind forces. Results show that aerodynamic loading is a key factor influencing mooring failure mechanisms: the upwind high-tension propensity increase by 13% and the downwind low-tension propensity by 39%. Wind-wave misalignment further increases these indicators by 2% and 5%, respectively, while nonlinear mooring dynamics provide additional increases of 1% and 5%.