Physics-Based Estimation of Boundary-Layer Bleed Requirement for an External-Compression Intake
11th International Conference on Recent Advances in Air and Space Technologies, Conference Program, RAST 2026, İstanbul, Turkey, 13 - 15 May 2026, (Full Text)
- Publication Type: Conference Paper / Full Text
- Doi Number: 10.1109/rast69551.2026.11672336
- City: İstanbul
- Country: Turkey
- Keywords: bleed slot sizing, boundary-layer bleed, computational fluid dynamics (CFD), shock-wave/boundary-layer interaction (SWBLI), supersonic inlet, total pressure recovery
- Middle East Technical University Affiliated: Yes
Abstract
The aerodynamic performance of a single-ramp external-compression intake designed for a nominal Mach number of 1.6 is investigated numerically over freestream Mach numbers of 1.4-1.9 and mass-flow ratios of 0.20-0.99 using Reynolds-averaged Navier-Stokes simulations validated against wind-tunnel pressure data. A boundary-layer bleed framework is introduced to estimate the required bleed demand from local compressible boundary-layer properties rather than from fixed empirical extraction fractions. A velocity-threshold parameter is used to identify the near-wall low-momentum layer targeted for extraction, and an optimum value is calibrated for each freestream Mach number. Under undisturbed conditions, the boundary-layer thickness at the bleed-entry station reaches a maximum near Mach 1.5, whereas the shape factor increases monotonically toward Mach 1.9, indicating a progressively greater susceptibility to separation. Under throttled low-mass-flow conditions, the shape factor rises well above the classical separation threshold, motivating active bleed. At the calibrated threshold, the cumulative momentum-deficit recovery reaches approximately 35-55% depending on the operating condition. The resulting Mach-mass-flow-ratio bleed maps show that the bleed requirement increases with freestream Mach number and decreases as the operating point approaches the high-flow branch. These maps provide a physically grounded preliminary input for subsequent bleed-slot sizing and integration.