Streamwise inhomogeneity of spectra and vertical coherence of turbulent motions in a finite-size wind farm

In a finite size wind farm turbulence is streamwise inhomogeneous. This paper examines the evolution of large scale motions on the order of 10 turbine rotor diameters influenced by wake-mixing from turbine rows. Using wavelet-based methods, the analysis illustrates that streamwise and vertically coherent length scales grow significantly past the first row of turbines. The first observation is primarily due to turbulence from the superposition of turbine wakes while the latter one is associated with the development of a global energy transfer mechanism (``sweeps'') between the outer layer and the wind turbine region.