Investigation of a Busemann Intake at Negative Angle of Attack

A high-speed, shape-transitioned, inward-turning intake was tested in Purdue’s Boeing/AFOSR Mach 6 Quiet Tunnel. The inlet model, called the Indiana Inlet (INlet), had a total contraction ratio of 4.68:1 and a design point of Mach 6 at a 0 deg angle of attack. The model was outfitted with a suite of high-frequency pressure transducers, and the external flowfield was imaged with high-speed schlieren photography. The INlet was tested under low freestream disturbance levels for a variety of freestream unit Reynolds numbers and at a [Formula: see text] angle of attack. An unsteady shockwave near the leading edge of the inlet forebody, indicative of boundary-layer separation, was detected from high-speed schlieren images in the [Formula: see text] angle-of-attack cases. The oscillation frequency of the unsteady shockwave matched low-frequency waves detected by surface-mounted pressure transducers. Downstream of the unsteady shockwave, a 20 kHz boundary-layer instability was detected by pressure transducers. The highest tested Reynolds numbers led to spectral broadening indicative of a transitional boundary layer within the mixed contraction region of the model. The existence and behavior of the unsteady shockwave suggest a coupling phenomenon between a hypothesized separation bubble and the 20 kHz boundary-layer instability. **