Numerical Investigation of Floating Offshore Wind Turbine Motion and Mooring Responses in a Co-Located Wind–Wave System with a Shared Mooring Line

Co-located floating offshore wind and wave energy systems offer a potential pathway toward sustainable offshore renewable energy development by sharing marine space and station-keeping infrastructure. This study numerically investigates the motion and mooring responses of a floating offshore wind turbine (FOWT) in a co-located floating wind–wave system, in which the FOWT and a point-absorber wave energy converter (WEC) are connected through a shared mooring line. A fully coupled OpenF2A time-domain model was established to simulate wind-turbine aero–servo–elastic responses, multibody hydrodynamics, PTO forces, and dynamic mooring responses. Parametric and comparative analyses were conducted for different FOWT–WEC spacings, wind and wave conditions, and environmental headings. The spacing effect was non-monotonic, and L/d = 11, corresponding to approximately 88 m, produced the lowest FOWT offset and relatively low finite-duration maximum mooring tensions among the examined cases. Wind-induced surge and pitch responses peaked near the rated wind speed, while more severe sea states mainly broadened the response distributions. The influence of the shared line was strongly direction-dependent and could increase FOWT offset, rotation, and individual mooring-line loads under unfavorable headings. These findings provide engineering insights into the reliable design of co-located wind–wave energy systems with shared mooring infrastructure, thereby supporting the sustainable development of offshore renewable energy.