  A thorough understanding of the energetic flow structures that form in the
far wake of a wind turbine is essential for accurate turbine wake modeling and
wind farm performance estimation. We use resolvent analysis to explore such
flow structures for a turbine operating in a neutral atmospheric boundary layer
and validate our results against data-driven modes extracted through spectral
proper orthogonal decomposition. Our results confirm that convective
instabilities play a dominant role in generating turbulent kinetic energy (TKE)
in the far wake. Additionally, we find evidence of the non-modal Orr mechanism
contributing to TKE generation, particularly at low Strouhal numbers. The
resolvent analysis method requires only the mean wake velocity and eddy
viscosity profiles as inputs but can capture the energetic modes and TKE
spectra in the far wake. In this specific application, the resolvent analysis
method approximates the wake to be axisymmetric, which suggests that it can be
paired with engineering wake models. Overall this study demonstrates the use of
resolvent analysis as a viable tool for estimating TKE and for uncovering the
mechanism of TKE generation.
