Stability and buzz characteristics of a Y-shaped conventional and diverterless supersonic inlet

The stability and buzz characteristics of a Y-shaped conventional intake (CI) and a diverterless supersonic intake (DSI) are numerically investigated at Mach 1.6 for sideslip angles of β=0° and 5°. Unsteady three-dimensional Reynolds-averaged Navier–Stokes simulations with the k–ω shear stress transport turbulence model are employed to analyze flow behavior across supercritical, critical, and subcritical operating regimes. The results reveal fundamental differences in shock structure, flow separation, and stability characteristics between the two configurations. The CI exhibits large-amplitude buzz instability at both sideslip angles, triggered by shock-induced boundary-layer separation at the splitter ramp and accompanied by substantial oscillations of the frontal shock system. Proper orthogonal decomposition of pressure fluctuations during buzz cycles reveals two distinct modes: a higher-frequency skew-symmetric mode and a lower-frequency symmetric mode with mode switching as back pressure increases. In contrast, the DSI demonstrates enhanced stability characteristics due to the distributed three-dimensional compression generated by the bump surface. At β=0°, no buzz is observed prior to unstart, while at β=5°, only weak oscillations associated with internal flow redistribution are observed. Although the CI achieves higher total pressure recovery at supercritical conditions, the DSI configuration exhibits lower distortion levels and a wider, stable operating envelope. These findings highlight the advantages of bump compression surfaces for enhancing supersonic inlet stability.