Design of a Wing with Boundary Layer Suction

Abstract

Over the last century lots of efforts have been put in the reduction of profile drag. By using advanced techniques in airfoil design, the passive ways to reduce profile drag by shaping have come to a standstill due to physical limits. To further reduce the profile drag, an active method has to be used. Boundary layer suction is one of these active methods and its effect is twofold. A laminar boundary layer will be stabilized, preventing transition and yielding larger areas of laminar flow, which generate less drag. On the other hand, turbulent boundary layer separation will be postponed, resulting in a higher maximum lift coefficient. In this thesis it is investigated how much improvement can be achieved by implementing boundary layer suction on the Euro-ENAER EE–10 Eaglet, a research aircraft of the Delft University of Technology. For this aircraft, a new airfoil has been designed in XFOIL which is optimized for boundary layer suction. The new airfoil proved to have good aerodynamic properties with and without suction and showed vast improvements in profile drag. Additionally, the maximum lift coefficient is increased significantly. Also the effects of boundary layer suction on flap and aileron deflection have been investigated. Results showed a significant decrease in drag and increase in maximum lift. With this newly designed airfoil, a new wing was created and its aerodynamic properties were calculated using the lifting line implementation of XFLR. The new wing proved to be more efficient, a drag reduction of 13% was achieved at cruise up to 20% at high flight speeds. However, the drag reduction of the total aircraft was marginally due to the high drag of the rest of the aircraft. At cruise the drag reduction of the total aircraft was about 3.2%.