Aerodynamic and wake characteristics of a full-scale 5 MW wind turbine: A data-driven modal decomposition study of wind shear and tower shadow effects

This study investigates the aerodynamic performance and wake evolution characteristics of the full-scale NREL 5 MW offshore wind turbine under four representative marine environmental conditions: wind shear, tower shadow, their combined effect and uniform condition. Numerical simulation and modal decomposition techniques are employed to analyze and extract wake flow features under these scenarios. Results show that under uniform inflow, the wake maintains an axisymmetric structure with a slow recovery of velocity loss. In contrast, wind shear accelerates wake recovery by exciting Kelvin–Helmholtz instabilities to form large-scale coherent structures, concentrating energy in low-order modes. The tower shadow generates small-scale vortex structures through periodic vortex shedding, creating a velocity deficit region near the hub. Under combined conditions, the two effects exhibit nonlinear coupling, resulting in the most complex wake morphology with the slowest recovery speed. POD analysis reveals that wind shear enhances large-scale coherent structures, while tower shadow promotes small-scale eddy formation. DMD further identifies distinct spatial modes and associated frequencies, and enhances the wave-like characteristics of the wake coherent structure, offering insights into the dynamic evolution of wake structures. This study provides theoretical support for the optimization of offshore wind farm layouts, floating platform design, and stability assessment of wind energy systems in marine environments.