# Wind Turbine Enhancement via Active Flow Control Implementation
## 4 Results
### Velocity and Pressure Fields for the Optimal \(\theta\), \(C_{\mu}\), and \(F^{+}\) Values  
In the present section, the streamlines, contours, and the pressure fields for the baseline case and the optimum AFC parameters implementation obtained from the parametric optimization are compared in Figure 13. It is evident that the AFC implementation has effectively reattached the flow on the entire airfoil and so has been able to maximize its aerodynamic performance. The location of the SJA is defined in Figure 13b. A comparison of the pressure contour fields between the baseline and the optimum actuated case shows a much larger low-pressure area on the airfoil upper surface than the one observed for the baseline case, therefore explaining the effect of the actuation on the pressure field and the associated lift increase, which is of 64.59%. It is as well remarkable to highlight the lift peak-to-peak amplitude reduction when applying AFC, such reduction being of 47.6%. This considerable boost in lift performance seen in Table 8 will be later used for the energy assessment and torque improvement of the DTU 10 MW RWT. Remarkable improvements can also observed in the drag coefficient when comparing the actuated case with the baseline case. Specifically, there has been a notable reduction in this parameter, amounting to an averaged decrease by 54.71%. Moreover, the drag peak-to-peak amplitude has decreased a 39.42% when compared with that of the baseline case. Such lift and drag peak-to-peak values decrease is extremely beneficial when considering the life expectancy of any WT, then sharply reduce the potential vibrations that could impact the blade. To determine the effects of these oscillatory drag and lift coefficients, a comprehensive structural analysis is required; however, it is out of the scope of the present work. The aerodynamic efficiency, as shown in Table 8, clearly demonstrates the positive impact of the AFC implementation on  
Figure 12: Lift coefficient (**a**), drag coefficient (**b**), and aerodynamic efficiency (**c**) variation as a function of forcing frequency; the vertical bars characterize the corresponding peak-to-peak amplitude. Constant momentum coefficient (\(C_{\mu}=0.007\)) and jet angle (\(\theta_{\text{jet}}=5\) deg. ). \begin{table}
\begin{tabular}{c c c c c c} \hline \(F^{+}\) & \(C_{I}\) & \(C_{d}\) & \(\eta\) & \(PTP_{C_{I}}\) & \(PTP_{C_{d}}\) \\ \hline
0.1 & 2.499 & 0.043 & 56.643 & 0.214 & 0.065 \\
0.5 & 2.524 & 0.067 & 37.856 & 0.059 & 0.057 \\
1 & 2.537 & 0.062 & 41.067 & 0.090 & 0.050 \\
2 & 2.569 & 0.050 & 51.325 & 0.218 & 0.085 \\
3 & 2.571 & 0.048 & 53.563 & 0.147 & 0.063 \\
4 & 2.576 & 0.052 & 49.897 & 0.381 & 0.086 \\
5 & 2.557 & 0.056 & 45.532 & 0.269 & 0.099 \\
10 & 2.560 & 0.099 & 25.932 & 0.557 & 0.110 \\ \hline
**BCS S54** & 1.562 & 0.106 & 14.71 & 0.281 & 0.104 \\ \hline \end{tabular}
\end{table} 
Table 8: Time-averaged aerodynamic coefficients \(C_{I}\), \(C_{d}\), and \(\eta\), and their respective peak-to-peak \(PTP_{C_{d}}\) and \(PTP_{C_{d}}\) amplitude, as a function of the SJ non-dimensional pulsating frequency. Momentum coefficient (\(C_{\mu}=0.007\)), jet angle (\(\theta_{\text{jet}}=5\) deg. ), groove position (\(x/C=0.4\)), and width (\(h=0.5\%C\)), are kept constant. the airfoil's lift-to-drag ratio. The reattachment of the flow, coupled with the increase in lift coefficient and the decrease in drag coefficient, has contributed to the mentioned significant efficiency improvement (264.12%). The non-dimensional turbulence viscosity fields for the baseline case and the optimum AFC parameters implementation are introduced in Figure 14. The locations where the Reynolds stresses are particularly high, which are the airfoil trailing edge (for the AFC case) and the area where the boundary layer is separated as well as the downstream zone (for the baseline case), are now clearly observed. In fact, an inverse relationship between the lift generated by the airfoil section and the area covered by high-turbulence viscosity can be established.