Blade-resolved improved delayed detached eddy simulation investigation of a pitching floating hybrid wind-tidal power system: energy-harvesting characteristics and decoupling prediction

Journal article, 2026

Aiming at the typical pitching response of floating hybrid wind-tidal power systems, this study conducts unsteady numerical simulations using a high-fidelity blade-resolved Computational fluid dynamics (CFD) framework with the Improved delayed detached eddy simulation (IDDES) turbulence model. The disturbance effect of pitch motion on the instantaneous power output of the upperwind turbine and lower tidal turbine is investigated, the spatiotemporal evolution mechanism of the three-dimensional wakevortex field under dynamic angle-of-attack distortion is elucidated, and a decoupling prediction model is established. Resultsshow that pitching-induced periodic tilt and angle-of-attack distortion markedly amplify nonlinear power oscillations but barelyaffect time-averaged energy harvesting performance, with the lower tidal turbine being more sensitive to motion excitation than the upper wind turbine; under extreme conditions, the wind turbine exhibits a 73.32% power fluctuation amplitude, whereas the tidal turbine undergoes torque reversal due to deep stall at large angles of attack, reaching a peak fluctuation of 105.93%. Pitching also disrupts the axisymmetric evolution of wake vortices, with the wind turbine wake featuring vertical spatial misalignment, while the tidal turbine wake deflects strongly and asymmetrically toward the rotation side under coupled tilt-rotation effects, accelerating vortex instability and premature breakdown. Furthermore, the least-squares-based decoupling prediction model agrees well with the improved delayed detached eddy simulation results and enables accurate evaluation of the hybrid device's energy harvesting performance. This work provides theoretical guidance for fatigue mitigation, stall suppression, and power smoothing control of multi-energy complementary marine energy systems.