摘要: The primary objective of the HIFiRE-1 flight experiment was to investigate boundary layer transition at high Mach numbers. The flight geometry was a 7-degree half-angle axisymmetric cone with a nose bluntness of 2.5 mm radius. An ... 展开 The primary objective of the HIFiRE-1 flight experiment was to investigate boundary layer transition at high Mach numbers. The flight geometry was a 7-degree half-angle axisymmetric cone with a nose bluntness of 2.5 mm radius. An anomaly in the exoatmospheric pointing manoeuvre resulted in much higher re-entry angles of attack during transition than initially anticipated, of approximately 5° -13°. Pre-flight ground experiments were conducted at angles of attack below 6°. This paper presents boundary layer instability measurements obtained in the Oxford High Density Tunnel (HDT) at the Reynolds number, Mach number, and angles of attack as experienced during the re-entry transition phase of flight. A sweep of Reynolds number and angles of attack were completed, to cover the range of conditions experienced during the HIFiRE-1 transition process. High-frequency surface pressure fluctuation results are given at a relatively fine resolution of azimuthal angles between the windward and leeward ray. Particular focus was given to the region where an indented transition front was observed in flight (φ ≈ 20° - 60°). The HDT results showed no evidence of this indented front, as the boundary layer destabilized directly when moving from the windward to the leeward ray. The windward ray boundary layer was more stable in the HDT than in flight. For azimuths (φ = 45° to the leeward meridian, the HDT transition occured at lower Re_x than in flight. These results are at a relatively high wall-to-total temperature ratio (≈ 0.64 instead of ≈ 0.18 for flight) and provide further insight into the three-dimensional laminar-to-turbulent transition experienced in flight. 收起