## 1 Introduction  
High lift devices such as leading edge (LE) slats and trailing edge (TE) flaps have been effectively employed for many years to increase the lifting performance of aircraft wings during take-off and landing. Conventional slats and flaps used by the aviation industry today consist of movable, split, or hinged mechanical sections with or without slotted surfaces. A modern alternative to the abovementioned articulated multi-element high lift devices is based on shape morphing concept, like the droop nose LE and the morphed TE. Mrapped wings can attain similar aerodynamic performance characteristics to those of conventional high lift devices by tailoring the shape (both mean-line curvature and local thickness distribution) of the wing airfoil sections through the deployment of smart material elements at the LE and TE regions. Smart materials have the property of altering their shape when variable external conditions are imposed (e.g., Shape Memory Alloys--SMAs--deform through heating and cooling). In this way, varying LE and TE shapes can be achieved using lightweight distributed actuators, acting locally on the smart material elements. By following the above approach vulnerable complex and heavy mechanical parts can be avoided. Additionally, a seamless surface geometry is attained eliminating large gaps or slots of multi-element devices, which constitute the main source of high frequency noise emission during take-off and landing. A typical example of morphing control is the droop nose airfoil, which compared to the traditional slat, exhibits lower drag levels (better aerodynamic performance) and better stall characteristics. However, the sole use of the droop nose wing cannot ensure as high levels of the maximum lift coefficient (\(\rm C_{L,max}\)) and the stall angle of attack (AoA) as those obtained by two- or three-elements slats. Research on high-lift devices has been carried out for several decades. [PERSON] and [PERSON] [1] studied the behavior of NACA23012 airfoil in a wind tunnel, using a Maxwell LE slat and a slotted and a split flap. Their target was to determine the optimum slot gap and investigate the aerodynamic characteristics of the airfoil for several deflection angles of both types of flap. The optimum slot gap of 0.0175% of the chord increased the \(\rm C_{L,max}\) and stall AoA considerably. The effectiveness of the slat, however, dropped off with increasing flap deflection. [PERSON] and [PERSON] [2] investigated the aerodynamic performance of NACA 64A010 with slat in a wide range of Mach and Reynolds numbers. Two families of slats were employed, one with the LE slat extended forward along the airfoil chord line, and the other with the slat extended forward and displaced below the chord line. At lower Mach number tests, the highest maximum lift values were measured with the slat nose displaced below the wing chord line. However, at Mach numbers higher than 0.7, adverse effects such as a large increase in drag and in the zero lift angle of attack resulted with the slat nose below the airfoil chord line. Until the beginning of 1990, substantial research effort focused on the determination of the optimum position for the different flap and slat types. Investigations included many different experiments, using either flap or slat or their combination. Moreover, the effect of high lift devices at different flight stages, speeds, and altitudes was analyzed. [PERSON] [3] made an extensive review of the available high-lift devices, their functions, and design criteria. He appraised the high-lift systems of the commercial aircrafts of his time, presented personal study results, and developed a weight and cost model. He concluded that there was still margin for improvement in terms of weight, cost, and aerodynamic performance, pointing to the direction of reduced complexity, increased reliability, and lower weight, while maintaining or improving aerodynamic performance. [PERSON] et al.