Optimizing a Two-Element Wing Model with Morphing Flap by Means of the Response Surface Method

Abstract

In designing the wings of UAVs, some factors such as the lift coefficient and lift-to-drag ratio (aerodynamic efficiency) play important roles in meeting the required fuel consumption, flight endurance, speed, reliability, maneuverability and runway length. One of the schemes presented for achieving the above objectives is the use of multi-element wings, in which high-lift mechanisms such as flaps and slats help the main airfoil. The recent advancements in the design of these mechanisms have made it possible to present a variety of morphing flap models that can perform adequately under different flight conditions. In the present research, a two-element wing model of a drone with medium-altitude and long-endurance capabilities and a morphing flap is numerically analyzed and the obtained results are compared with and validated by the empirical data obtained from wind tunnel tests. For optimizing the flap shape to achieve the maximum aerodynamic efficiency of the wing, the response surface method is used as a design of experiments technique. In this approach, several geometrical parameters that indicate the position and curvature of a flap were defined and different arrangements of these parameters are presented as experiment designs, then the aerodynamic efficiency of the wing for each design of experiment is determined numerically and the optimum design is proposed. The results show that the factors of flap curvature and vertical distance of flap to the main airfoil have a significant effect on the aerodynamic efficiency of the considered wing.