Nosetip bluntness effects on a cone-cylinder-flare at mach 6.

A cone-cylinder-flare model with sharp and blunt nosetips was tested at the AFRL Mach-6 Ludwieg Tube at a 0 ∘ angle of attack. Surface-pressure fluctuation measurements, high-speed schlieren images, and surface-heat-transfer measurements were taken to study instability and transition as related to an axisymmetric separation bubble downstream of each nosetip. Three nosetip radii were tested, nominally sharp (0.1 mm), 1 mm, and 5 mm. Time-averaged schlieren imagery revealed a smaller bubble for the sharp and 1 mm nosetips than for the 5 mm nosetip. Heat flux measurements revealed streamwise streaks downstream of reattachment that increased in prominence with increasing nosetip bluntness. Surface pressure measurements and high-speed schlieren images include fluctuations below 100 kHz that traverse downstream in the shear layer and the reattached boundary layer for all three nose radii. Wisp-like structures similar to those seen with other blunt geometries were observed traveling downstream in the shear layer over the bubble for the 5 mm nosetip. Nosetip bluntness resulted in delayed transition relative to the sharp tip, with the effect being more significant for the 5 mm nose than for the 1 mm nosetip. [ABSTRACT FROM AUTHOR]