Blade-Resolved IDDES Investigation into the Fully Coupled Dynamic Responses of a Floating Horizontal-Axis Tidal Turbine Under Focused Wave–Current Loading

The wave–current interaction in realistic marine environments significantly alters the flow field structure, turbine hydrodynamic loads, and platform motions of floating tidal turbines and represents a critical factor governing their fully coupled dynamic responses and operational stability. In this paper, a high-fidelity blade-resolved fully coupled numerical model is established based on the improved delayed detached-eddy simulation (IDDES) method to investigate the effects of focused wave height and frequency bandwidth on the hydrodynamic performance and platform motion responses of a standalone floating horizontal-axis tidal turbine under focused wave–current loading. The results show that increasing wave height intensifies flow turbulence and wake vortex distortion in the flow domain. Under the maximum-wave-height condition, the fluctuation amplitude of the power coefficient is 1.46 times that in the low-wave-height case, thereby inducing an asymmetric load distribution on the blades. Waves with a narrow frequency bandwidth suppress blade pressure fluctuations. The extreme difference in the pressure coefficient at the blade root is reduced by 43% compared with that under the broadband condition, effectively improving load uniformity. Under focused wave–current loading, platform surge and pitch exhibit distinct response characteristics as the wave parameters vary. These platform motions directly affect the transient power and hydrodynamic load responses of the turbine. This study elucidates the fully coupled dynamic response mechanisms associated with variations in focused-wave parameters and provides a theoretical basis for the optimal design of tidal energy devices operating in complex wave–current environments.