Decoupling wind shear from atmospheric boundary layer forcing to systematically unravel wind turbine wake dynamics*

In atmospheric boundary layer (ABL), friction and Coriolis forces balance pressure gradient forcing to form the structure of the mean wind and turbulence. Wind turbines operate in the ABL, generating wakes through the extraction of mean kinetic energy that negatively impact turbine performance downwind. Many factors influence these wakes, including turbulence, Coriolis forces, thermal stratification, and the ABL velocities, which ubiquitously contain wind speed and direction shear. But wind speed and direction shear are themselves coupled with the balance of forces in the ABL, and further depend on many additional variables, including heating history, orography, and subsidence. Due to this coupling, the effects of each ABL phenomenon on wake dynamics have been challenging to study independently. To isolate the wake dynamics associated with each ABL phenomenon, large eddy simulations (LES) of elementary flows are systematically used to decouple wind shear from Coriolis forces, stratification, and turbulence. Through the analysis of momentum and turbulence budgets, these ABL effects on wake dynamics are parsed into forcing and transport processes. Finally, LES of wind turbine wakes in realistic, stratified ABL conditions are compared with the elementary flows. Transport mechanisms in the ABL are constructed from elementary flows, aiming toward the development of a generalized wake model that captures ABL phenomena from first principles.