Componentwise influence of upstream turbulence on the far-wake dynamics of wind turbines

Wake meandering and turbulent kinetic energy (TKE) generation in the far-wake region of wind turbines significantly affect the power production and aerodynamic loads of wind farms. This work thus aims at understanding the componentwise influence of upstream turbulence and roles of different mechanisms on the far-wake dynamics to guide the development of wind-farm wake models. We find that the wake meandering is mainly caused by the upstream spanwise (v ') and vertical (w ') velocity fluctuations, supporting the passive wake meandering mechanism. However, our results also show a scale-dependence of the wake meandering that should be accounted in wake models. We find that v ' and w ' cause greater TKE generation than the streamwise velocity fluctuations (u '). We then use simulation- and resolvent-based componentwise input-output analyses to explain that this is because the shear instability in turbine wakes is more receptive to the transverse forcing relative to the streamwise forcing. This highlights the importance of implementing the shear instability mechanism in wake models for accurate TKE estimations. Finally, we find that u ' cause the thrust fluctuations, which can lead to near-wake corrections and hence influence the far-wake evolution.