Shock Control by Adaptive Elements for Transportation Aircraft Wings

Kurzfassung

Different devices for the application of shock and boundary layer control on transportation aircraft wings have been investigated on 2-d airfoils and on a swept wing model. A cavity in the surface underneath the foot of the shock covered with a perforated plate reduces shock strength and hence wave drag, but viscous drag increases such that a net drag reduction can not be achieved in most cases. The application of additional boundary layer suction reduces the additional viscous drag, but not enough to result in a significant gain in total drag. On the contrary a contour bump underneath the shock, applied alone or in combination with suction, reduces very effectively wave drag without increasing viscous drag so that under off-design conditions up to 24% total drag reduction has been measured for a 2-d airfoil and somewhat lower values for the swept wing. This effect has been well predicted by numerical methods. Both devices, especially the perforation, have a positive influence on the buffet boundary. Trailing edge devices such as conventional and Gurney-type flaps also effect wave drag by redistributing the pressure on the wing or airfoil. Combining them with a contour bump has been investigated numerically. The results show that by careful optimization of the flap deflection together with the corresponding bump location and height a better performance can be achieved compared to the application of either device alone.