Comparisons between the wake of a wind turbine generator operated at optimal tip speed ratio and the wake of a stationary disk

The wake of a wind turbine generator (WTG) operated at the optimal tip speed ratio is compared to the wake of a WTG with its rotor replaced by a stationary disk. Numerical simulations are conducted with a large eddy simulation (LES) model using a nonuniform staggered Cartesian grid. The results from the numerical simulations are compared to those from wind-tunnel experiments. The characteristics of the wake of the stationary disk are significantly different from those of the WTG. The velocity deficit at a downstream distance of 10 D (D: rotor diameter) behind the WTG is approximately 30 to 40 of the inflow velocity. In contrast, flow separation is observed immediately behind the stationary disk (≤2D), and the velocity deficit in the far wake (10 D) of the stationary disk is smaller than that of the WTG.