Turbulence Modeling for the Stable Atmospheric Boundary Layer and Implications for Wind Energy

The near-surface structure of atmospheric turbulence affects the design and operation of wind turbines and is especially difficult to predict under stably-stratified conditions. This study uses large-eddy simulation (LES) to explore properties of the stable boundary layer (SBL) using an explicit filtering and reconstruction turbulence modeling approach. Simulations of the atmospheric boundary layer over flat terrain, under both moderately and strongly stable conditions are performed. Results from high-resolution simulations are used to investigate SBL flow structures including mean profiles and turbulence statistics, which are relevant to wind energy applications. The applicability of power-law relations and empirical similarity formulations for predicting wind speed depend on the strength of stratification and are shown to be inadequate. Low-level jets form in the simulations. Under strong stability, vertical wind shear below the jet triggers intermittent turbulence. The associated sporadic “bursting” events are extremely energetic and last longer than the time scale of the largest eddies. Such phenomena can have adverse effects on turbine lifetime and performance.