Low speed wind tunnel investigation of the aerodynamic and acoustic performance of several sonic inlet takeoff and approach geometries

A series of tests was conducted to determine the aerodynamic and acoustic performance of several sonic inlet takeoff and approach geometries. The effects of inlet lip shape and diffuser length were also investigated. The tests were conducted in a low-speed wind tunnel at free-stream velocities of 0 and 45 meters per second. Inlet incidence angle was varied from 0 deg to 50 deg. The inlets were sized to fit a 13.97-centimeter-diameter fan. In terms of the highest level of inlet total pressure recovery for a given amount of noise suppression, a cylindrical centerbody takeoff geometry and a bulb-shaped centerbody approach geometry provided the best results over all conditions of free-stream velocity and incidence angle. Increasing inlet lip contraction ratio extended the maximum incidence angle for attached lip flow, while increasing inlet diffuser length resulted in a higher total pressure recovery for a given amount of noise suppression