Some observations on the aerodynamics of an airfoil with a jet exhausting from the lower surface

A preliminary investigation was carried out to study the aerodynamics of an 18% symmetrical airfoil with a rectangular jet exhausting from the lower surface. Static pressures on the airfoil surface and total pressures in the near wake were measured at jet momentum coefficients ranging from 0 to 2. Results from these measurements were used to study the effects of a jet-cross flow interaction on the aerodynamics of an airfoil. These results were also compared with those obtained from a two-dimensional inviscid theoretical model. Measurements indicate positive and negative pressure regions in front of and behind the jet respectively. The intensity of the pressure in these regions increases with increasing jet strength. Upper surface pressures also decrease due to an effective angle of attack induced by the jet-cross flow interaction. The pressure variations on the upper and lower surfaces induce a positive sectional lift coefficient on the airfoil. The magnitude of the lift coefficient for a given momentum coefficient decreases with decreasing aspect ratio of the nozzle.