## 3 Results
### Experimental Results  
After recording the rotation velocity and the torque exerted between the rotor and the braking electric motor, the power generated for each recorded instant (\(0.05\,s\)) was calculated. Finally, the average of the torque and power values corresponding to the same rotation regime was determined and it was carried to dimensionless terms (Figures 17 and 18). Since the numerical and experimental data were obtained in test sections with the same blockage ratio, any source of variation between both approaches should not be found. In Figure 17, it can be seen that the \(C_{T}\) curves conserve their order of succession of the three rotors in each approach, with the multi-blade Bach profile being the one with the highest performance both in the numerical and in the experimental one. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline  & \begin{tabular}{c} **Number of** \\ **Treatments** \\ \end{tabular} & \begin{tabular}{c} **\(R^{2}\)** \\ \end{tabular} & \begin{tabular}{c} **\(Adjusted\)** \\ \(R^{2}\) \\ \end{tabular} & \begin{tabular}{c} **\(Modeled\)** \\ \(C_{P}\) \\ \end{tabular} & \begin{tabular}{c} **\(Numerical\)** \\ \(C_{P}\) \\ \end{tabular} & \
\begin{tabular}{c} **\(\dfrac{\dfrac{\text{}}{\text{}}}{\text{}}\) \\ \(O\) \\ \end{tabular} &
\begin{tabular}{c} **Stationary Point** \\ \(P\) \\ \end{tabular} \\ \hline FFD & 27 & 0.9391 & 0.9068 & 0.4161 & 0.4364 & 96.8085 & 17.4275 & 9.4000 \\ FCCD & 15 & 0.9650 & 0.9021 & 0.4205 & 0.4215 & 97.1827 & 16.6731 & 8.6566 \\ \hline Difference & \(-44.44\%\) & 2.76\% & \(-0.52\%\) & 1.06\% & \(-3.41\%\) & 0.39\% & \(-4.33\%\) & \(-7.91\%\) \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Comparative between the FFD and FCCD designs. Figure 16: Significance level for the different factors and interactions in the FFD and FCCD designs (the black line represents the maximum significance level of 0.05). Similarly, in Figure 18, it can be seen that the relationship between the results of \(C_{P}\) of the three rotors is significantly conserved within each approach, revealing that the difference between the multi-blade Bach profile and the split Bach profile is about half the difference between the latter and the conventional semicircular profile. The differences presented between the results of the numerical study and the experimental one may be mainly due to friction. In the simulations, the rotor turns freely and the effects of the supports are neglected, which causes a reduction in the angular velocity and, consequently, modifies the values of the \(TSR\) at which the different characteristic points are achieved in the rotor's performance curves. Similarly, when the rotor attempts to come to a complete stop, the transition that occurs between dynamic and static friction at the point of imminent movement generates slight torsional pulses on the sensor shaft that alter measurements and cause values to be recorded; the torque increased to low \(TSR\) (Figure 17). Moreover, the roughness on the blades surface affects the relationship between the aerodynamic coefficients of the profiles \((C_{L}/C_{D})\), causing performance to decrease [44]. In the numerical study, smooth rotors were evaluated, but during experimentation, the models were used, although they had a good surface finish, they were not ideal. On the other hand, considering that the wind velocity is the variable with the greatest significance in the estimation of rotor performance, because it is at the third power, any minimum deviation (either due to calibration or resolution of the measuring instrument,  
Figure 17: Results of \(C_{T}\) obtained experimentally by the three tested rotors (E) and their comparatives with the numerical results determined from the three-dimensional simulations (N). Figure 18: Results of \(C_{P}\) obtained experimentally by the three tested rotors (E) and their comparatives with the numerical results determined from the three-dimensional simulations (N).