Hypersonic Boundary-Layer Instabilities over Cone-Flare Models*

Cone-flare geometries exhibit a shock-wave/boundary-layer interaction with high surface heating in the reattachement region. Computational investigations of a cone-flare geometry with varying nosetip radii and flare angle at zero degrees angle of attack are presented. The model geometry and conditions are selected to match the experiments conducted in the Air Force Research Laboratory (AFRL) Mach 6 Ludwieg Tube. Four nosetip radii of interest are used for the computational studies herein: 0.1, 0.5, 5.1, and 10.2 mm. These nosetips are attached to a 7-degree half-angle circular cone which is followed by a flare with angle varying from 34, 37, 40, and 43-degrees. Peak surface heating was measured at the reattachement location, which is located slightly past the cone-flare junction. Streamwise heat flux streaks were measured at the reattachement location on the flare and the azimuthal spacing was reported for all conditions. The laminar boundary layer solution is computed using the VULCAN-CFD solver on a single-block structured grid, with the built-in options for shock alignment and boundary-layer grid adaptation enabled. Global instability analysis is performed to identify possible correlations between global mode wavelength and the spacing of heat flux streaks observed experimentally.