Large-eddy simulation associated with the low level jet under moderate to strong stable conditions

The low-level jet (LLJ) is a nocturnal boundary layer phenomenon that is usually located 100 to 300 m above the ground. The nature of the LLJ, a thin stream of fast moving air, makes it favorable for wind energy capture. Strong vertical wind shear near the LLJ, however, is a potential source for elevated turbulence which could impose adverse stresses on the wind turbines and possibly shorten their lifespan. Therefore, accurate numerical simulations for the night-time stable boundary layer (SBL) become essential for wind power forecasting and turbine micrositing. We use a large-eddy simulation approach to model the SBL. An explicit filtering and dynamic reconstruction method following Chow et al.(2005) is adopted to improve the representation of subfilter scale turbulence. The LLJ is simulated under a wide range of atmospheric stabilities, from moderate to strongly stable conditions with intermittent turbulence. Elevated turbulent kinetic energy around the jet is investigated. Results are sensitive to the atmospheric stability, the explicit filtering and reconstruction operation, as well as the ability of the turbulence model to predict shear production and backscatter of turbulence near the LLJ.