Design and Analysis of a Droop Nose for Coanda Flap Applications

The present study describes the fundamentals of droop nose design for improving the aerodynamics of airfoils with active high-lift using an internally blown Coanda-type flap. The main objectives are to increase the stall angle of attack and reduce the power required by the high-lift system. A two-dimensional sensitivity analysis explores the effects of varying airfoil camber and thickness in the first 20% of the chord. The resulting droop nose configuration improves the maximum lift coefficient by about 20% and increases the stall angle of attack by around 10–15 deg. A target lift coefficient of about 4.7 is reached with 28% less jet momentum coefficient, compared to the clean nose. As the modified leading-edge geometry presents different stall mechanisms, the aerodynamic response to variations of jet momentum is also different. In particular, for a jet momentum coefficient above 0.035, the stall angle of attack increases with jet momentum, in contrast with the behavior observed with the clean nose.