## 3 Discussion and Results
### Morphing Trailing Edge Optimization  
The optimization process defined in Section 3.1 was implemented on the MTE airfoil by using the same two optimization functions defined by Equation (1) for drag minimization and by Equation (5) for endurance maximization. The optimization of the Morphing Trailing Edge (MTE) airfoil shape for the three flight conditions given in Table 5 was performed. The optimization processes were carried out for two types of MTE control points. In the first type, referred to as Opt. Case I, MTE is a smooth single shape with a morphing starting point and trailing edge end point. The leading edge is not allowed to move, while the trailing edge points are only allowed to move in the vertical direction with respect to the baseline airfoil. In the Opt. Case II, the MTE is a three-segmented finger-like configuration. The points are outlined to represent the morphing trailing edge starting location, the length of the first segment and the length of the second segment. The morphing location was kept at x/c = 0.60, so that enough space was provided for the actuation mechanism, and which is where its upper and lower limits were given as constraints. The upper bounds and the lower bounds were chosen to prevent the generation of morphing airfoil shapes with no likelihood of having very good aerodynamic efficiency. XFoil was used as an aerodynamic  
Figure 18: Velocity magnitude and turbulent kinetic energy contour plots. (**a**) Velocity contour lines at low angles of attack such as 4\({}^{\circ}\); (**b**) Velocity contour lines at low angles of attack such as 10\({}^{\circ}\); (**c**) the turbulent intensity at a low angle of attack of 4\({}^{\circ}\); (**d**) the turbulent intensity at a low angle of attack of 10\({}^{\circ}\). solver and therefore as a powerful tool that allowed obtaining fast convergence solutions. The results were later validated by the use of a RANS models in Ansys/Fluent solver. Figure 19a illustrates the initial (reference) versus the final (optimized or morphed) airfoil shape, while Figure 19b illustrates the convergence trend for the minimum drag optimization function for an optimized airfoil shape with MTE at an angle of attack of 50. It is seen that the graph in Figure 19b trends to a constant after some iteration steps, which shows convergence to its optimal solution. The first set of results obtained for MTE for different flight conditions are shown in Figure 20a-d. The lift coefficients are presented for the three different flight conditions in the two different cases of Opt. Case I and Opt. Case II. The lift coefficients of the optimized airfoil design have higher values than those of the baseline airfoil; therefore, the optimized shapes produce an improvement of the lift coefficient with respect to the baseline airfoil of up to almost 26%, as seen in Figure 20c for Opt. Case I. In addition, an increase of 8% is obtained for the maximum lift coefficient for the optimized airfoils with respect to the baseline airfoil. Figure 21 presents the evaluation of the lift versus drag variation (polar) of the baseline airfoil and the optimized airfoils for different flight conditions. The increased aerodynamic performance of optimized airfoils for all three flight conditions can be seen in Figure 21a-d. The pressure coefficients of the MTE airfoil cases at three different flight conditions are shown in Figure 22. It can be observed that the suction peaks of the optimized airfoils are higher than those of the baseline airfoil. The MTE airfoil results expressed in terms of \"effective camber change\" lead to a significant increase in the negative pressure value at the trailing edge surface. The low performance of the baseline airfoil compared to that of the optimized airfoils can be related to the unfavorable pressure gradient on its upper surface near the leading edge, thereby causing an earlier laminar-turbulent transition of the boundary layer by slightly increasing the drag. Figure 19: Optimized airfoil and convergence history for drag minimization function.