Wind Turbine Wake Dynamics and Associated Thermal Interactions Over a Diurnal Cycle

The atmospheric boundary layer (ABL) undergoes significant changes in its structure and dynamics throughout a typical diurnal cycle. These changes can affect the behavior of wind turbine wakes in wind farms. The wakes can, in turn, alter convective heat transfer over the ground surface, leading to two-way coupling and spatial heterogeneity in surface heat fluxes. Here, we investigate the impact of spatially heterogeneous surface heat fluxes on the temperature field, as well as the wake flow structure and power time series within a wind farm during a diurnal cycle using LES. We apply a concurrent precursor inflow method, an advanced filtered actuator-line approach to represent wind, and a local 1D soil heat conduction model coupled with the LES. we incorporate Coriolis forcing that induces wind veer, causing the mean wind direction in the precursor domain to continuously vary over a 24 hour period. LES results obtained after periodic behavior is achieved and reveal that wind turbine wakes have a significant impact on the temperature field, causing increased surface temperatures behind the wind farm at night. During the morning transition, the wind farm blockage effect results in a reduction in wind speed at hub height upstream of the wind farm. Meanwhile, the formation of a low-level jet and the enhanced turbulent kinetic energy at the last row of the wind farm lead to increased velocities experienced by turbines in that area. Consequently, for a few morning hours, the first row of wind turbines generates less power compared to the last row. The generated dataset will be made available for public access through the JH turbulence database.