Flow-around airfoils with blunt, round, and sharp trailing edges

Abstract

Attached and separated boundary layers were arranged on the suction side of a plate with a sharp trailing edge and compared to those around blunt and round trailing edges. Pressure and velocity characteristics were obtained with wall taps, impact probes, stationary and flying hot wires in the boundary layer, separated and wake flow regions. With the trailing plate inclined at 14 deg incidence and the boundary layer attached, the effect of the geometry of the trailing edge was confined to the near-wake region and was important mainly in the determination of base pressure. With the trailing plate at 17.5 deg incidence and turbulent boundary-layer separation, the structure of the separated and wake flow regions was significantly affected by the trailing-edge geometry. The results suggest that accurate calculation of lift, drag, and the onset of separation on airfoils as a function of incidence requires representation of the effects of trailing-edge shape and thickness on the pressure gradients in the direction across the boundary layer and in the streamwise direction, especially in the wake, on the turbulence structure of the backflow and, accordingly, on the rate of turbulence diffusion, upstream and downstream of the trailing edge, which determines the location and size of the recirculation region.