Boundary Layer Transition on Slender Cones in Conventional and Low Disturbance Mach 6 Wind Tunnels

Abstract

An exlJeriuwntal investigation was conducted on a 5-degree ha!f angh' cone and a 5-degree ha!lLangh" .]lared

Direct numerical simulation of hypersonic boundary layer transition over a blunt cone with a small angle of attack

“…Lots of wind tunnel and flight experiments are performed to measure the transition locations on supersonic/hypersonic blunted or sharp cone boundary layers. 7,8 These experimental results show that transition onset Reynolds numbers for flight experiments are much larger than that for the wind tunnel ones, and the tunnel noise is deemed as the main reason. Horvath et al 8 conducted experimental investigations on 5°half-angle cones in a conventional wind tunnel and a Mach 6 quiet wind tunnel, and the influence of tunnel noise was studied by comparing the transition onset locations obtained from convectional tunnel test with that obtained from quiet tunnel test.…”

“…7,8 These experimental results show that transition onset Reynolds numbers for flight experiments are much larger than that for the wind tunnel ones, and the tunnel noise is deemed as the main reason. Horvath et al 8 conducted experimental investigations on 5°half-angle cones in a conventional wind tunnel and a Mach 6 quiet wind tunnel, and the influence of tunnel noise was studied by comparing the transition onset locations obtained from convectional tunnel test with that obtained from quiet tunnel test. The comparison shows that the transition onset Reynolds number un-der low disturbance conditions was a factor of 1.3-1.6 greater than that measured in the conventional hypersonic tunnel or run in the quit tunnel run "noisy."…”

“…The comparison shows that the transition onset Reynolds number un-der low disturbance conditions was a factor of 1.3-1.6 greater than that measured in the conventional hypersonic tunnel or run in the quit tunnel run "noisy." In addition, leading bluntness, angle of attack, and wall roughness effects on transition onset location are also discussed in the report of Horvath et al 8 Experimental results show that leading bluntness affects the transition location significantly. The increase in leading bluntness can retard the transition location, but the effect will be reversed when the bluntness exceeds a threshold.…”

“…Experimental researches show that even a very small angle of attack ͑such as 1°͒ can affect the transition locations of cone boundary layer significantly. 8,12 The authors 13 performed the DNS of boundary transition over a blunt cone with free-stream Mach 6 and 1°angle of attack, trying to answer the question why transition is early in the leeward section and is delayed in the windward section. Limited by computer resource, only the flow around the leeward and the windward sections is simulated in the DNS, 13 while the whole distribution of transition locations on the cone surface is not studied.…”

Discrete Roughness Transition for Hypersonic Flight Vehicles

“…In Ref. 13 the relative disturbance environment of the Mach 6 facility (conventional) was deduced from comparisons of smooth wall transition onset locations measured on high-fidelity conical models to results previously obtained in the LaRC Mach 6 Nozzle Test Chamber (NTC) Quiet Tunnel (see , reaching the conclusion that while the conventional Mach 6 tunnel is slightly noisier than the quiet NTC facility, it is not nearly as noisy as NTC in the "noisy" mode. References 18 and 19 document the corresponding RMS free-stream noise levels using several hotwire methods and confirms that the noise levels associated with the 20-In Mach 6 tunnel falls between the NTC levels when quiet and noisy.…”