Characterizing Unique Bi-Stability Pattern in Mach 5 Inlet Buzz Phenomena

Inlet buzz is an unsteady flow instability in high-speed intakes, affecting stability and engine performance. This study investigates buzz development in a 2D planar intake with a 10° ramp in Mach 5 flow, where exit blockage increases using fixed orifice plates. Schlieren imaging at 66 kHz is used to investigate the flow dynamics. At 28% blockage, big buzz appears with a dominant frequency of 290 Hz, modulating between 245–330 Hz over time. It is accompanied by precursor little buzz oscillations, creating a bi-stable flow pattern. As blockage increases, the oscillation shifts to a more stable big buzz mode, with frequencies rising to 491 Hz at 40% and 543 Hz at 50%. The amplitude of these oscillations initially grows, then stabilizes. Shock-boundary layer interaction and upstreamshock motion drive these changes, shifting the separation bubble and forming an effective throat. The findings reveal a previously unreported bi-stability, where flow alternates between large-scale big buzz oscillations and intermittent little buzz-like structures, providing new insight into how blockage affects inlet stability.