Large eddy simulation (LES) is used as a tool to understand the near-wake effects of large 5-MW, 3-blade horizontal-axis wind turbines (WT) in convective atmospheric boundary layer (ABL). The simulations are performed for two inline WT separated by distance of 2.5D (D is diameter of the rotor) in unstable ABL so that the downstream WT is operated under the wake of the upstream WT. The flow characteristics are analyzed in the wake regions behind WT to understand the flow physics. Tip and root vortices undergo vortex merging due to instability. Turbulent mixing layer that develops in the wake region is stronger for the downstream WT. The rate of growth/decay of the mean velocity and turbulence is much higher for WT2 than WT1. The time evolution of the wake of WT1 and WT2 revealed additional wake induced shear that contributes to faster turbulence diffusion which results in shrinking of the shear layer (in height) downstream. The average power output of WT2 is 40% lower than WT1 during unstable stratified atmospheric conditions.
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