A comparative study of different rotor designs for enhancing the coupled performance of semi-submersible floating vertical-axis wind turbines

Floating vertical-axis wind turbines have attracted increasing interest for deep-water offshore wind applications, but a key challenge remains before they can be deployed at utility scale – the lack of a unified design. Given the diversity of blade geometries, the selection of rotor configuration is challenging, especially because systematic full-scale models accounting for coupled aerodynamic, hydrodynamic, and mooring effects under realistic sea conditions remain scarce. To address this gap, full-scale models of two representative configurations (H-type and Φ-type) are developed with identical swept areas and key geometric parameters. A coupled aero-hydro-mooring analysis framework is established using computational fluid dynamics by integrating dynamic fluid-body interaction with a volume-of-fluid model, and is applied to compare their dynamic responses under combined wind-wave loading. Results show that the Φ-type configuration benefits from its closed blade-end connection and root-concentrated supports in the low tip-speed region, which reduce the blockage and negative torque associated with the large-span supports of the H-type configuration, increasing the power coefficient by 11.04%. Unlike the coherent blade-tip vortices of the H-type configuration, the blade-end vortices of Φ-type configuration mainly develop as circumferential shear layers along the closed boundary, promoting momentum exchange and turbulent mixing during downstream propagation. Its smaller upwind projected area also reduces platform surge drift and mooring tension under aerodynamic thrust, indicating better global dynamic stability. Frequency-domain analysis further reveals that wave excitation and drift forces dominate periodic platform motions and affect rotor aerodynamics, while blade-rotation-induced unsteady loads introduce high-frequency fluctuations in platform rotational degrees of freedom.