Influence of atmospheric boundary layer on turbulence in wind turbine wake

Full-scale wind turbines (WT) operate in the atmospheric boundary layer. The atmospheric boundary layer structure significantly influences the turbulence generated in the wake of the WT. As Atmospheric boundary layer structure is dictated by the stratification of the atmosphere, hence stratifications effects are critical in accurate representation of the turbine wake physics. Due to the dependency of several factors, such as turbulence scales, buoyancy flux, momentum flux, the atmospheric boundary layer turbulence capturing is really challenging. Large Eddy Simulation (LES) has been used as a tool to understand the effects of atmospheric stability on turbine wake turbulence. The differences between the stable and unstable atmosphere on wake of 5-MW turbine has been explored. Differences in tip and root vortex interactions, wake expansion and recovery have been analyzed. The study has revealed for stable ABL low level jets play an important role in wake dynamics and increasing stability delays the wake recovery. Tip vortex is unconditionally unstable in all stability conditions due to mutual inductance mode of stability leading to vortex merging. The study is one of the first studies that accounts for realistic atmospheric boundary turbulence on wake development.