Effects of heterogeneous surface heat flux on wind turbine wakes in LES over a diurnal cycle*

The atmospheric boundary layer (ABL) undergoes significant changes in its structure and dynamics throughout a typical diurnal cycle, which can consequently affect the behavior of wind turbine wakes in wind farms. These wakes can, in turn, alter convective heat transfer over the surface terrain, leading to two-way coupling and spatial heterogeneity in surface heat fluxes. In this work, we examine the effects of using different types of surface boundary conditions for the temperature field in Large Eddy Simulations (LES) of wind farms. The most commonly applied boundary conditions are imposed temperature or heat flux, but these approaches cannot account for the above-mentioned two-way coupling. To address this issue, we combine an LES wind farm model using a filtered actuator-line approach for the wind turbines with a simple local 1D soil heat conduction model. We compare the results related to the diurnal cycle and heterogenous thermal effects with those obtained using a prescribed heat flux or surface cooling rate instead of the 1D soil model.  In particular,  we investigate the influence of thermal effects on wake recovery behind the wind turbines. The generated datasets are planned to be shared publicly via an extension of the JHU turbulence database (JHTDB).