*3.1. Specifics of the Employed Turbine Design*

A full-scale wind turbine and a subscale wind turbine are studied in this work as shown in Figure 1. The diameters of the two turbines are 80 m and 27 m, respectively. The full-scale turbine T80 is located 93.3 m above the ground, while the subscale turbine T27 is located 31.5 m above the ground. The T27 turbine is designed by Kelley et al. in [30] (Design A). The T80 turbine is designed by simply scaling the T27 turbine, such that the radial distributions of the twist angle and the normalized chord length (as shown in Figure 2) are the same for the two turbines. It is noticed that the T27 turbine has the same rotor diameter and hub height as the SWiFT turbine but with different designs as shown in Figure 2 and Table 1. The scaling ratio is chosen in a way the size of the full-scale turbine is similar to that of a land-based wind turbine. The radial distribution of the airfoil shapes is shown in Table 1. For the present cases, the tip speed ratio is 9. The power coefficient, *CP* = *<sup>P</sup>* 0.5*ρπR*2*U*<sup>3</sup> (where *P* is the power, *R* is the rotor radius, *D* is the rotor diameter, and *U* is the incoming wind speed), is 0.47 and 0.49 for the turbine T80 and T27, respectively. The thrust coefficient, *CT* = *<sup>T</sup>* 0.5*ρπR*2*U*<sup>2</sup> (where *T* is the thrust), is 0.65 and 0.68 for the turbine T80 and T27, respectively. The incoming wind speed *U* employed for calculating *CP* and *CT* is obtained by averaging the time-averaged velocity over a disk of radius *R* parallel with the rotor rotating plane and located 1*D* upwind of the turbine. The same lift and drag coefficients are employed for both turbines to ensure dynamic similarity and to simplify the problem such that the only two differences are the turbine size and the inflow.

**Figure 1.** Schematic of the two turbines of different sizes employed in this work. Large blue turbine: T80, diameter *D* = 80 m, hub height *zh* = 93.3 m; small green turbine: T27, diameter *D* = 27 m, hub height *zh* = 31.5 m.

**Figure 2.** Radial distributions of (**a**) twist angle and (**b**) chord length. The twist angle and the normalized chord length are the same for turbines T80 and T27. Black lines: the employed turbine design; Red circle: SWiFT turbine design.


**Table 1.** Distribution of airfoil shapes along the radial direction [30]. The information in parentheses shows the airfoil shape distribution of the SWiFT turbine [31].
