# Wind Turbine Enhancement via Active Flow Control Implementation
## 4 Results
### Velocity and Pressure Fields for the Optimal \(\theta\), \(C_{\mu}\), and \(F^{+}\) Values
For the case of optimum AFC parameters implementation, it is now seen that small vortical structures are expected at the airfoil trailing edge; turbulence viscosity is particularly large at this point, highlighting the particularly large momentum interchange between the fluid particles. It appears as if the boundary layer was about to separate just before the airfoil trailing edge. In order to further clarify the effect of the synthetic jet on the flow just downstream of the groove location, the SJ oscillation period has been divided into six equal time steps and presented in Figure 15. At the initial time shown in this figure, what we called time \((0/6)T\), the outgoing jet velocity is maximum, \(u_{\text{jet}}(t)=u_{\text{max}}\), and the turbulence viscosity is particularly high at the jet exit and downstream of it. The streamlines are suffering a particularly high curvature under these conditions. As the outgoing jet velocity decreases, (1/6)T and (2/6)T, the streamlines curvature as well as the turbulent viscosity downstream of the injection area also decrease. When the suction phase starts (3/6)T, the streamlines just upstream of the jet location start bending inwards, with this bending curvature maximum at (4/6)T, which coincides with the maximum incoming jet velocity. The turbulence viscosity around the jet location during the suction phase appears to be particularly low. Figure 14: Streamlines of temporal average velocity field and contours of non-dimensional turbulence viscosity in Section 54 for the baseline case (**a**) and maximum lift case (**b**). Figure 13: Streamlines of temporal average velocity field and contours of averaged pressure in Section 54 for the baseline case (**a**) and optimum AFC implementation case (**b**). The pressure coefficient analysis, as shown in Figure 16a, provides insights into the behavior of the actuated and baseline cases, and a comparison between the two reveals notable differences. In the actuated case, there is an evident increase in the suction peak near the leading edge in reference to the baseline case. Moreover, the pressure recovery on the upper surface of the airfoil is smooth, indicating the absence of flow separation. This is in contrast to the baseline case, which exhibits a sharp gradient of the pressure coefficient, suggesting the presence of separated flow. Notice as well that the pressure below the airfoil is higher in the AFC case than in the baseline one. The analysis of the tangential friction coefficient (\(C_{f}\)) in Figure 16b provides valuable insights into the flow behavior along the airfoil's surface. In the case of the AFC implementation, it is observed that the SJ generates a sudden rise of the friction coefficient, which prevents it from becoming negative at any point along the chord of the airfoil, which suggests that the flow remains attached throughout the entire airfoil. In contrast, in the baseline case, flow separation is clearly observed at \(x/c=0.423\). Figure 17 provides a comparison between the time-averaged velocity profiles tangent to the airfoil for both the AFC (actuated) and baseline cases. Regarding the AFC case, it is observed that the velocity distribution is positive at all points, therefore matching the profile of a non-separated flow. Moreover, the increase in velocity near the jet injection region is clearly visible, indicating the impact of the synthetic jet on the external flow. On the other hand, the baseline case exhibits a negative velocity distribution pattern from \(x/c=0.423\) to \(x/c=1\), indicating the occurrence of flow separation in all this zone. Figure 15: Instantaneous velocity streamlines and non-dimensional turbulence viscosity at different phases of the synthetic jet for the maximum lift case in Section 54. \(F^{+}=3\), \(C_{\mu}=0.007,\theta=5^{\circ}\).