Hypersonic boundary-layer transition measurements at Mach 10 on a large seven-degree cone at angle of attack
The ability to predict the onset of boundary-layer transition is critical for hypersonic flight vehicles. The development of prediction methods depends on a thorough comprehension of the mechanisms that cause transition. In order to improve the understanding of hypersonic boundary-layer transition, tests were conducted on a large 7° half-angle cone at Mach 10 in the Arnold Engineering Development Complex Wind Tunnel 9. Twenty-four runs were performed at varying unit Reynolds numbers and angles of attack for sharp and blunt nosetip configurations. Heat-transfer measurements were used to determine the start of transition on the cone. Increasing the unit Reynolds number caused a forward movement of transition on the sharp cone at zero angle of attack. Increasing nosetip radius delayed transition up to a radius of 12.7 mm. Larger nose radii caused the start of transition to move forward. At angles of attack up to 10°, transition was leeside forward for nose radii up to 12.7 mm and windside forward for nose radii of 25.4 mm and 50.8 mm. Second-mode instability waves were measured on the sharp cone and cones with small nose radii. At zero angle of attack, waves at a particular streamwise location on the sharp cone were in earlier stages of development as the unit Reynolds number was decreased. The same trend was observed as the nosetip radius was increased. No second-mode waves were apparent for the cones with large nosetip radii. As the angle of attack was increased, waves at a particular streamwise location on the sharp cone moved to earlier stages of growth on the windward ray and later stages of growth on the leeward ray. RMS amplitudes of second-mode waves were computed. Comparison between maximum second-mode amplitudes and edge Mach numbers showed good correlation for various nosetip radii and unit Reynolds numbers. Using the e N method, initial amplitudes were estimated and compared to freestream noise in the second-mode frequency band. Correlations indicate that freestream noise likely has a significant influence on initial second-mode amplitudes.
Schneider, Purdue University.
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