# Wind Turbine Enhancement via Active Flow Control Implementation
## 4 Results  
### Baseline Case Results Summary  
Delving into the results of the baseline case simulations, it will initially present the numerical values encompassing the time-averaged lift \(C_{l}\) and drag \(C_{d}\) coefficients, the peak-to-peak (PTP) variations of the parameters \(PTP_{C_{l}}\) and \(PTP_{C_{d}}\), the aerodynamic efficiency \(\eta\), the non-dimensional boundary layer separation points \(x_{\text{sep}}/C\), and the dimensional vortex shedding frequencies \(f_{0}\). For the specific numerical values already mentioned, the reader should refer to Table 5, where the comparison of the lift and drag coefficients obtained from previous research work [51; 53] is also presented. From the data presented in this table, several key insights can be gleaned about the behavior of the blade's middle sections at moderate wind speeds. It becomes evident that they share common traits such as a heightened lift-to-drag ratio and rather small peak-to-peak oscillation magnitudes. Furthermore, it is noteworthy that the oscillation frequencies remain relatively subdued for Section 54, whereas for Section 81, and due to the fact that there is no boundary layer separation, small vortical structures are just appearing at the airfoil trailing edge, the oscillations occur at a much more rapid rate. The comparison of the lift coefficient of Sections 54 and 81 with previous reference values shows errors of 7.5% and 1.6% versus the ones given in reference [53]; respectively, such \(C_{l}\) discrepancies are of 2.5% and 16% when compared with the respective values obtained in [51]. As already presented in Table 4, the \(C_{d}\) error versus the present Section 54 and the results from [51] is of around 32%, this error being of 330% when compared with [53]. The already reported differences in chord length and Reynolds number between the present research and the one from [51] clarified the origin of the discrepancies. To understand the origin of the \(C_{d}\) discrepancies versus the 3D results presented by [53], it needs to be noted that in their research no boundary layer separation was observed in this particular section, probably due to the much coarser mesh they used; then their reported y+ was around 2, while it is around 0.7 in the present simulations. Note as well the large discrepancies in the lift and drag coefficient values presented in these two [51; 53] references, therefore indicating that much more accurate simulations are needed to properly determine the boundary layer dynamics as well as the force coefficients; the present research is a small step in this direction. In order to have an illustrative overview of the data presented in Table 5, Figure 8 provides the time-averaged of the streamlines at the upper surface of the two airfoils studied as well as the time-averaged of the pressure fields. The location where the fluid has a maximum acceleration, the area where time-averaged pressure is minimum, is almost the same for both sections. The vortical structures forming on top of Section 54 and its associated boundary layer separation point can now be clearly seen. The very small vortical structures having a frequency of around 28.8 Hz are not spotted from the view presented of Section 81. Yet this information is obtained from the Fast Fourier Transformation (FFT) of the dynamic lift signal. Delving into the post-processing graphs, Figure 9a,b present the pressure and friction coefficients comparison for the two sections studied, from where it is seen that a high lift coefficient is directly linked to a large pressure coefficient below the airfoil and a particularly low pressure coefficient on the airfoil upper surface. In Section 54, there is a pronounced suction peak on the upper surface near the leading edge, followed by a rapid pressure recovery and subsequently, a nearly constant value of \(C_{p}\). This observation suggests a potential flow separation near that particular location.