Flow Asymmetry in a Y-Shaped Diverterless Supersonic Inlet: A Novel Finding

Abstract

Extensive wind-tunnel tests were performed on a Y-shaped diverterless supersonic inlet (DSI). All tests were conducted at a free stream Mach number of , the design Mach number for this inlet, and at both zero degrees angle of attack (AOA) and angle of sideslip (AOS). The experiments were performed at various inlet operating conditions comprising supercritical, critical, and subcritical conditions that covered almost all ranges of the engine operating for this DSI. The results showed that the DSI had relatively acceptable performance characteristics when operating at its design condition. A symmetric supersonic flow pattern was observed at both supercritical and critical operating conditions of the present Y-shaped DSI. However, both symmetric and asymmetric supersonic flow patterns were observed during the subcritical operating conditions of the present inlet. At low subcritical operating conditions, the supersonic flow pattern remained symmetric, similar to that of the critical operating condition case. As the inlet experienced higher subcritical operating conditions, the supersonic flow structures became suddenly asymmetric and a new flow pattern was noticed. This flow pattern was seen to be highly unstable; and significant asymmetric shock wave oscillations, boundary-layer thickening, and shock-/boundary-layer interaction were observed for these situations. To the authors’ knowledge, this novel phenomenon of asymmetric flow behavior in a perfectly manufactured symmetric Y-shaped DSI encountering symmetric flow (0 deg AOA and AOS) has not been noticed by previous researchers and, if so, the results have not been published yet.