*2.6. General DLC Setup*

The DTU 10 MW RWT is a state-of-the-art reference rotor, developed in recent years as a benchmark for researchers and industry in the field of wind energy. It features a 178-meter diameter rotor with aerodynamic features like gurney flaps that help this conceptual turbine reach a rated power of 10 MW at a wind speed of 11.4 m/s. The tower height is 119 m and the nominal revolution speed is 9.6 rpm, which equates to a tip speed just shy of 90 m/s. The complete definition of the turbine and all of its parameters can be found in Bak et al. [11]. To estimate the AEP of the turbine, a power-production design load case (DLC) is simulated. This is done through sixty-six 10-minute simulations with wind speeds at a hub height between 4 and 24 m/s. Six turbulent seeds per wind speed are simulated, in compliance with the minimum requirements of the IEC 61400-1 [30]. The wind fields also feature wind shear and misaligned flow with respect to the rotor plane. By simulating several cases, uncertainties regarding atmospheric conditions are dealt with, and their influence is accounted for in this study.

It is important to note that turbulence affects power production and other key turbine figures in a complicated manner, as this depends both on the interaction between the controller and the incoming wind speed and on the complex blade boundary-layer phenomena amongst other things. The interaction between large turbines and the turbulent atmospheric boundary layer is out of the interest of the present study and has been evaluated in detail by Churchfield et al. and Nandi et al. [31,32]. Moreover, as other authors have pointed out when studying a similar multi-MW wind turbine in an aero-servo-elastic modelling framework [20], six turbulent realizations are enough to guarantee good convergence on the AEP statistics.

AEP is calculated using a Rayleigh wind-speed probability density function with a mean of 10 m/s as specified by IEC class IA, which is the design class of the DTU 10MW. The AEP obtained using a Rayleigh distribution with a mean wind speed of 8.5 m/s (corresponding to IEC class IIA) will also be briefly analyzed as this could be more representative of the impact of blade damage on sites with lower mean wind speeds.

#### **3. Results**

The aPC resulting collocation points are qualitatively shown in Figure 5 and detailed in Table 2. For each point, the corresponding damaged airfoil geometry is generated and CFD calculations were

performed as described in Section 2.3. With the resulting airfoil data, aero-servo-elastic BEM simulations were performed as described in Section 2.4.

**Figure 5.** Arbitrary polynomial chaos (aPC) resulting collocation points' plot in ε–τ space.

**Table 2.** aPC optimal collocation points values.

