Instability and Transition on the HIFiRE-5 in a Mach-6 Quiet Tunnel
PURDUE UNIV LAFAYETTE IN SCHOOL OF AERONAUTICS AND ASTRONAUTICS
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A 21 aspect-ratio elliptic cone with a blunt nosetip was tested in the Boeing AFOSR Mach-6 Quiet Tunnel to investigate the effects of freestream noise level, surface roughness, angle of attack, and freestream Reynolds number on laminar-to turbulent boundary layer transition on the windward surface. The cone had a minor axis half-angle of 7-deg and a nose radius of 0.95 mm. Temperature-sensitive paint enabled a global measurement of the temperature distribution and detection of the transition front. Transition apparently arising from two mechanisms was observed transition along the centerline suspected to arise from the amplification of second mode waves in the inflected boundary layer, and transition roughly halfway between the centerline and leading edges probably due to the breakdown of cross flow vortices. Reducing noise level from conventional root-mean-square pressure 3 of the mean to quiet root-mean-square pressure less than 0.1 of the mean substantially delayed transition due to both mechanisms. Increasing the angle of attack from 0-deg to 4-deg delayed the cross flow transition mode on the windward side. Transition moved forward as free stream unit Reynolds number increased from 2.6-deg 106 m to 11.9-deg 106 m. PCB fast-response pressure transducers installed along the model centerline detected apparent instabilities at frequencies from 50 to 150 kHz prior to transition under noisy flow quiet-flow results are less clear. Mass flux profiles along the centerline were measured with a calibrated hot wire.
- Theoretical Mathematics