Drag Reduction and Buffet Damping by a Contour Bump Control Device and Regional-jet Application

Summary

In the present work Alenia (ALN) has performed an evaluation of shock control by contour bumps in order to explore their capability to reduce the wing drag in transonic flow and to allow damping of aerodynamic buffet. Evaluations on 2D airfoils have been performed using the ALN Navier-Stokes code. Indications have been obtained that a local, well designed, upper surface deformation (bump) can sensibly reduce airfoil drag in transonic flow in a large range of lift coefficients. The bump, when effective in drag reduction, also dampens buffet. At off-design conditions, the bump effectiveness vanishes very rapidly and, in some cases, the bump may increase drag and/or induce buffet. ALN has also generated a simplified configuration of a regional jet for which numerical evaluations have been made. The results obtained indicate that benefits can be gained only at the design point, and that even a reduction in efficiency may occur at off-design conditions. It is concluded that, to obtain a true benefit from the application of bump devices, the adoption of more advanced techniques is needed, such as generating a bump shape through multipoint optimisation or developing an adaptive bump device.