Impact of utility-scale wind turbine wakes on surface fluxes

Added turbulence in the wake of a wind turbine can influence the flux of momentum, heat, and moisture at the ground surface, affecting agriculture and ecology in the surrounding environment. However, this effect is not well understood at the field scale because of the lack of techniques available to analyze this phenomenon in detail. In the current study, super-large-scale particle image velocimetry (SLPIV) using natural snowfall is employed with a field-of-view spanning from the ground to 49 m above and covering the region 87 m downwind of a utility-scale turbine. This dataset reveals strong interaction between coherent tip vortex structures in the wake and the ground surface. The strength of these interactions is found to depend on the turbine operation, including the tip-speed-ratio, blade pitch, and yaw error. Additionally, the effect of the interaction on the fluxes at the surface is quantified. This improved understanding of the physical phenomena causing this behavior provides insights into discrepancies between previously published field-scale observations of wind farm induced effects on surface fluxes. These effects can be considered in the future for the optimization of wind farm siting and operation with respect to impact on the environment and plant efficiency.