Experimental aerodynamics characteristics of the airfoils LA 5055 and DU 86-084/18 at low Reynolds numbers.

Abstract

Presents results obtained in the low speed low turbulence wind tunnel (Delft University) for two low Reynolds number aerofoils the LA 5055, and the LSL's DU 86-084/18. Lift and pitching-moment data were obtained from pressure measurements (LA 5055) and balance measurements (DU 86-084/18) and drag data from wake surveys. The fluorescent oil flow technique was used to visualize the flow behaviour. Design features of the LA 5055 airfoil are a distinct destabilizing region between 27% and 47% chord followed by a Stratford type pressure recovery distribution. To prevent early separation near the tunnel walls, suction was applied in a small region on the walls along the airfoil contour. In spite of the destabilizing region, drag producing laminar separation bubbles were present, and drag reductions up to 33% were measured by applying a zig-zag tape turbulator for transition control. The maximum lift coefficient, being governed by the Stratford limiting pressure distribution, could be raised by 38% with semi triangluar vortex generators positioned at 20% chord. (A)