Airfoils In Two Dimensional Nonuniformly Sheared Slipstreams

A theoretical and experimental program was conducted to investigate the aerodynamics of an airfoil in a two-dimensional nonuniformly sheared slipstream. A mathematical model was developed to predict airfoil pressure distributions in such a slipstream and was used successfully for slipstreams with moderate shear. Pressure distributions over a wide angle of attack range were measured experimentally on an airfoil at each of seven different locations in a highly sheared two-dimensional slipstream. Study of the pressure distributions obtained on the airfoil at a location slightly above the flow centerline and also at a location slightly below the flow centerline indicates that the large effects on stalling characteristics are due to differences in the upper surface pressure distributions. These pressure distributions are affected by the freestream shear. Moreover, in the data obtained for airfoils located near the flow centerline, the differences in the lift appear to be caused primarily by differences in the stagnation pressure of the streamline which intersects the airfoil. This stagnation pressure is a function not only of airfoil location relative to the slipstream, but also of the angle of attack of the airfoil. (Author).