A wind-tunnel investigation was carried out to characterize the spatial distribution of the\nintegral time scale (Tu) within, and in the vicinity of, two model wind farms. The turbine arrays\nwere placed over a rough wall and operated under high turbulence. The two layouts consisted\nof aligned units distinguished only by the streamwise spacing (Ã?â?xT ) between the devices, set at\nfive and ten rotor diameters dT (or Sx = Ã?â?xT/dT = 5 and 10). They shared the same spanwise\nspacing between turbines of 2.5dT; this resulted in arrays of 8 Ã?â?? 3 and 5 Ã?â?? 3 horizontal-axis turbines.\nHotwire anemometry was used to characterize the instantaneous velocity at various vertical and\ntransverse locations along the central column of the wind farms. Results show that Tu was modulated\nby the wind farm layout. It was significantly reduced within the wind farms and right above them,\nwhere the internal boundary layer develops. The undisturbed levels above the wind farms were\nrecovered only at ââ?°Ë?dT/2 above the top tip. This quantity appeared to reach adjusted values starting\nthe fifth row of turbines in the Sx = 5 wind farm, and earlier in the Sx = 10 counterpart. Within the\nadjusted zone, the distribution of Tu at hub height exhibited a negligible growth in the Sx = 5 case;\nwhereas it underwent a mild growth in the Sx = 10 wind farm. In addition, the flow impinging the\ninner turbines exhibited Tu/Tu\ninc < 1, where Tu\ninc is the integral time scale of the overall incoming\nflow. Specifically, Tu ââ? â?? Ã?²Tu\ninc at z = zhub, where Ã?² < 1 within standard layouts of wind farms, in\nparticular Ã?² ââ?°Ë? 0.5 and 0.7 for Sx = 5 and 10.
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