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A 38.1%-scale model of the Hypersonic International Flight Research Experimentation Program's Flight Five 2:1 elliptic cone flight vehicle was used to investigate the traveling crossflow instability in a Mach 6 quiet wind tunnel. Traveling crossflow waves were detected with pressure sensors mounted flush with the model surface. The crossflow instability phase speed and wave angle were calculated from the cross spectra of the three pressure sensors. Both quantities showed good agreement with linear stability theory. Duplicate runs at the same initial conditions showed excellent repeatability in traveling crossflow wave properties. Traveling crossflow waves in quiet flow showed very low levels of nonlinear interactions. No traveling crossflow waves were observed for any Reynolds number for elevated freestream noise levels, but transition occurred for a much lower Reynolds number than in quiet flow. Due to the lack of nonlinear growth in quiet flow and the absence of traveling crossflow waves in noisy flow, it appeared that the traveling crossflow instability was not the primary transition mechanism on the model for quiet or noisy flow in this wind tunnel. [ABSTRACT FROM AUTHOR]

The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight test program executed by the Air Force Research Laboratory and Australian Defence Science and Technology Organisation. The principal goal of HIFiR E flight five is to measure hypersonic boundary-layer transition on a three-dimensional body. The HIFiRE flight tests are supported by a ground test campaign; this paper presents measurements of heat flux and boundary-layer transition in the Boeing/AFOSR Mach-6 Quiet Tunnel. This facility has been developed to provide quiet flow at high Reynolds number, with low noise levels comparable to flight. This tunnel's good optical access enabled global measurement of the heat flux by means of temperature-sensitive paint. Two modes of transition were observed: transition along the centerline, suspected to arise from the amplification of second-mode waves in the boundary layer, and transition roughly halfway between the centerline and leading edges, probably due to the breakdown of crossflow vortices. Reducing the noise level from conventional to quiet substantially delayed both transition modes. Increasing the angle of attack from 0 to 4 deg delayed the crossflow transition mode on the windward side. Transition moved forward as freestream unit Reynolds number increased from 2.6 ⋅ 106/m to 11.9 106/m. [ABSTRACT FROM AUTHOR]

• Boundary-layer separation and reattachment is identified with IR thermography. • Classical scaling analyses for separation length apply to a cone/flare geometry. • Peak heating scales with the inviscid density ratio across the separation shock. Time-resolved surface temperature measurements have been carried out on a 7 ° half-angle circular cone/flare model in the Air Force Research Laboratory's Mach-6 Ludwieg Tube using infrared thermography. Measurements were performed at zero angle of attack on a total of 16 different nose bluntness/flare angle geometries at three different freestream unit Reynolds numbers. The boundary layer entering the interaction region was turbulent for the two sharper nosetips and laminar for the two blunter nosetips. Stanton-number contours and profiles were used to investigate the effect of nose bluntness, flare angle, and freestream unit Reynolds number on the length of boundary-layer separation and the peak heating achieved upon reattachment. The classical scaling analyses of Souverein et al. and Hung & Barnett for separation length and peak heating, respectively, have been extended for the use of axisymmetric cone/flare shock-wave/boundary-layer interactions. Scaling the peak heating with the density ratio across the separation shock wave, instead of the pressure ratio, significantly improves/simplifies the analysis. [ABSTRACT FROM AUTHOR]