Wake Meandering

The present chapter deals with wake meandering -- its physics, its modeling, and its consequences for production and loading of wind turbines erected in wind farms. Wake meandering is the phenomenon describing the dynamics of wind turbine wakes. Nowadays there is almost unanimous agreement in the wind energy community that wake meandering is caused by large turbulent eddies in the atmospheric boundary layer. In the introductory part of this chapter, an accounting of the development leading to this conclusion will be given. This includes both full-scale experiments using advanced lidar technology, scaled wind tunnel experiments using both boundary layer wind tunnels and conventional wind tunnels, and last, but not least, detailed unsteady computational fluid dynamics large eddy simulations with wind turbines modeled as actuator lines. Recognizing the fundamental physics behind the wake meandering phenomenon, both high-fidelity and medium-fidelity modeling approaches are described. Being related to large-scale turbulence structures in the atmospheric boundary layer, impact from atmospheric boundary layer stability should be expected, and this important aspect is therefore also included in the modeling part. The chapter is concluded with various example applications ranging from wind turbine production prediction over wind turbine load prediction to optimal wind farm layout, for which both accurate production and load prediction are needed.