Aerodynamic Performance on a Wing Using Passive and Pneumatically Active Engine Nacelle Strakes

Abstract

The aerodynamic interactions at the nacelle-wing junction create complex flow structuresthat promote localized flow separation, increase aerodynamic drag, and reduce aircraft effi- ciency. To mitigate these aerodynamic penalties, this thesis experimentally evaluated pas- sive and active pneumatic nacelle-mounted strakes installed at the nacelle-wing junction of a semi-span wing model representative of a Boeing 737-800 wing planform. Low-speed wind tunnel experiments were conducted over a wing angle of attack (α) range from −5◦ to 20◦ under representative cruise, takeoff, and landing conditions with flap deflection angles (δf ) of 0◦, 20◦, and 45◦. Aerodynamic performance was evaluated using measurements of lift co- efficient (CL), drag coefficient (CD), and lift-to-drag ratio (L/D). The results demonstrated that the effectiveness of both passive and active strakes depended strongly on flap deflection and flow control configuration. Passive strakes reduced CD, increasing L/D by up to 36.5% during cruise and 22.8% during landing, but generally degraded performance during takeoff because drag increases outweighed modest lift increases. Active strakes achieved the greatest improvement during cruise, increasing L/D by 42.9%, but reduced aerodynamic efficiency during takeoff and landing for the same reason. These findings demonstrate that effective nacelle-wing flow control depends on matching the flow control strategy to the surrounding aerodynamic environment.