Effects of inflow turbulence on wind turbine loads and wakes for blade-resolved simulations*

Wind turbines in atmospheric boundary layer (ABL) routinely encounter varying wind speeds and turbulence. To optimize the design of turbine blades, it is of great importance to understand the complex interaction between wind turbines and ABL. In this work, the effects of inflow turbulence on the unsteady aerodynamic loads, frequency statistics and wake characteristics are investigated for the NREL Phase VI turbine under axial-flow conditions. Two methods are employed for generating inflow turbulence. The first approach defines turbulence conditions at the inlet and estimates the turbulent kinetic energy decay from the inlet to the turbine location. The second method employs synthetic turbulence generator to inject resolved turbulence. The simulations are performed using Shear-Stress Transport (SST) and Improved Delayed Detached Eddy Simulation (IDDES) turbulence models. Comparison of the power spectral density (PSD) based on the thrust coefficient as well as the resulting Strouhal number is performed. The effects on velocity deficit and turbulent intensity are also examined both in the near- and far-field wake regions.