Experimental investigation and dataset release of a taut-leg mooring system for a semi-submersible floating offshore wind turbine

In the offshore wind energy field, reducing energy costs involves optimizing and analyzing each system component. A key component influenced by the installation site is the mooring system, which can be designed using various concepts. This study focuses on examining a taut-leg mooring system and its impact on the overall system behavior. Due to a lack of experimental data on taut-leg mooring systems for Floating Offshore Wind Turbines (FOWTs) in the existing literature, our work aims to provide the scientific community with an extensive experimental dataset to validate various numerical models and support the design process of a taut-leg mooring system for a selected installation site. The full-scale mooring system was designed, scaled down, and evaluated through experiments at a 1:96 scale using a mooring configuration realized with springs. Springs offer a constant axial stiffness, reflecting the ideal structural behavior. Our paper highlights significant observations for this configuration, even under off-design conditions with modified pre-tension levels. Regular and irregular waves were tested to establish a baseline hydrodynamic response, assess the wind turbine's impact on the floater, and evaluate operating conditions. An environmental contour (EC) was defined to analyze the system's behavior in ultimate and accidental limit states. System identification (ID) waves streamlined the characterization process by reducing the number of required waves. Additionally, free decay tests were performed to assess the system's dynamic characteristics at resonance. The analysis of experimental data reveals that pre-tension variations minimally influence the dynamics of the floating structure. Results showed that the tested mooring system exhibits stability during power production and withstands ultimate and accidental limit states.