## 3 Aerodynamic Design and Performance of the Morphing Winglet
### Study of Morphing Winglet Configurations  
Then, the use of morphing flaps adapted to this winglet has been assessed in term of possible aerodynamic performances. The adopted convention considers a positive deflection when it moves outward. For the present analysis, the same deflection applied at the same hinge location was considered for the upper and lower flaps. Only one \"failure\" case, with positive deflection on the upper flap and negative on the lower flap, has been considered. Figure 14 presents the different configurations considered by CFD evaluations for positive flap deflections. The angles considered were \(3^{\circ}\), \(5^{\circ}\) and \(10^{\circ}\), applied either on hinge 1 (upper line) or hinge 2 (lower line). \begin{table}
\begin{tabular}{c c c} \hline
**Cruise: Turbulent** & **Cruise: Free Transition** & **Climb: Free Transition** \\
**CL = 0.50** & **CL = 0.50** & **CL = 0.84** \\ \hline \(\Delta\)L/D = +0.89\% & \(\Delta\)L/D = +1.45\% & \(\Delta\)L/D = +2.68\% \\ \hline \end{tabular}
\end{table} 
Table 1: Comparison of Reference and CIRA winglets performance at design points. Figure 13: Reference and CIRA winglets: comparison of aerodynamic performance at cruise conditions (M = 0.52 @ 20,000 ft). (**a**) Lift Polar (C\({}_{\rm L}\)(\(\alpha\))); (**b**) Drag Polar (C\({}_{\rm L}\)(C\({}_{\rm D}\))); (**c**) C\({}_{\rm L}\) (C\({}_{\rm m}\))curve, (**d**) C\({}_{\rm L}\) (C\({}_{\rm L}\)/C\({}_{\rm D}\)) curve. Considering the negative deflections (Figure 15), only one case (\(-5^{\circ}\)) was considered. Some problems occurred for larger negative values in the grid deformation tool, with local grid inversion leading to \"negative cells\" in the field, due to the concave topology used in the baseline grid. Finally, a kind of \"failure\" case was considered, with \(+10^{\circ}\) deflection on the upper flap, and \(-5^{\circ}\) for the lower flap, both applied on hinge 1. Computations were carried out around the \(\text{C}_{\text{L}}\) value, corresponding to the design cases. Several flight conditions have been considered and numerical results have been sent to partners for local force analysis on the different elements for sizing cases. In this paper, only the reference cruise (M = 0.52 @ 20,000 ft) and climb (M = 0.36 @ 15,000 ft) are presented. All the results presented in this document are at \"aircraft\" level. The force and moment coefficients considered the entire aircraft surfaces for pressure and friction integration. Figure 14: Mophed winglet configurations considered: Positive deflections. Figure 15: Mophed winglet configurations considered: Negative deflections and failure case. (**a**) 1 st hinge line: \(-5^{\circ}\), 2 nd hinge line: \(0^{\circ}\); (**b**) 1 st hinge line: \(0^{\circ}\), 2 nd hinge line: \(-5^{\circ}\); (**c**) “Failure” case: \(+10^{\circ}\) (upper flap); \(-5^{\circ}\) (lower flap), both applied on 1 st hinge line. Figure 16 presents the \(\mathrm{C_{L}}(\alpha)\) curves computed at cruise or climb conditions for the different morphed winglet configurations considered. The results obtained for the Reference initial winglet (black curve) and the new winglet (CIRA winglet) with no morphing (red curve) are given for comparison. These results show that the morphed winglet device can be used as a surface control on the aircraft for load alleviation. As a basic result, it can be seen that the larger the deflection or the flap length, the larger the \(\mathrm{\Delta C_{L}}\). It can also be noted that some combinations are nearly equivalent in terms of \(\mathrm{C_{L}}(\alpha)\). For instance, applying a global deflection of \(3^{\circ}\) on hinge 1 or \(5^{\circ}\) on hinge 2 leads to the same \(\mathrm{\Delta C_{L}}\). In terms of improvements in the aerodynamic performance around the design flight point, the use of a morphed winglet seems very limited. Figure 17 presents the LoD obtained for the different configurations. At cruise conditions, there is no gain observed around the flight \(\mathrm{C_{L}}\).