Dynamic responses of a 5 MW floating vertical-axis wind turbine: a hybrid wave basin test study with precomputed aerodynamic loads

Abstarct Floating vertical-axis wind turbines (VAWTs) are promising for deep-water wind energy, but basin-scale experiments remain challenging because model-scale rotor aerodynamics cannot be reproduced consistently under Froude-scaled conditions. This study presents a hybrid model test framework with precomputed aerodynamic loads for investigating the dynamic responses of a 5 MW semi-submersible floating VAWT in the wave basin. Aerodynamic thrust and lateral forces are generated numerically and reproduced by a propeller-based loading device. The experimental system was characterized through aerodynamic-load validation and restoring stiffness, free-decay, hammer, and white-noise tests. The reproduced tower-top forces retained identifiable 3P aerodynamic harmonics with stronger narrow-band concentration in the lateral-force component. Tower-top accelerations showed clearer sensitivity to the imposed harmonic content and local upper-structure dynamics than the global platform motions. Platform motions were dominated by low-frequency natural modes and wave-frequency response, with weak higher-order aerodynamic harmonics in roll. Supporting numerical simulations reproduced the principal platform-response frequencies and showed good agreement in surge fluctuations under wind-only loading and pitch fluctuations under combined loading. Mooring tensions exhibited direction-dependent mean-load redistribution and retained limited high-frequency signatures in selected line groups. These results support hybrid testing of floating-VAWT responses under controlled and repeatable multi-directional aerodynamic excitation.