Mach 6 freestream calibration of Φ0.6 m low-level-noise experimental platform and measurement of instability waves of sharp cone

Ground experiment is one of the important means of aerodynamics research. For experimental investigations of transition and turbulence, the wind tunnels should keep a low level of freestream noise. Utilizing fast-acting valve with large diameter and following the conception of Ludwieg tubes, the State Key Laboratory of Aerodynamics constructed a Φ0.6 meter low-level-noise hypersonic experimental platform (SKLA-TT1 for short), which is suitable for conducting researches on turbulent and transition mechanisms. Firstly, the composition of SKLA-TT1 is briefly introduced, together with a detailed description of the fast-acting valve. It is found that the start-up time of the fast-acting valve is about 19 ms. Secondly, preliminary freestream calibration of the SKLA-TT1 is conducted using pitot rakes and pitot tubes. Results show that the effective running time of the experimental platform is about 130 ms. Moreover, SKLA-TT1 controlled by the fast-acting valve shows high flow quality. The Mach 6 of SKLA-TT1 has excellent flow uniformity and flow quality, the normalized RMS pitot pressure fluctuations are 0.36～0.56 % in the test region for unit Reynolds number from 8.0 × 10⁶ to 25.0 × 10⁶/m. Thus, this facility shows promising potential in experimental studies on key aerodynamic fundamental scientific issues such as hypersonic turbulence and transition. The wall pressure signals of a sharp cone show that there are the second mode waves with high frequencies in the boundary layer. When the location moving downstream, the second mode waves first grow and then gradually disappear into turbulence-like power special denticity.