Analysis of Second-Mode Amplitudes on Sharp Cones in Hypersonic Wind Tunnels

Abstract

This research effort coordinated by the NATO Science and Technology Organization Applied Vehicle Technology 240 specialists’ group compiles and analyzes second-mode amplitudes on sharp slender cones. The analysis focuses on pressure fluctuations measured with piezoelectric sensors in 11 hypersonic wind tunnels operated by nine organizations located in three NATO countries (Belgium, Germany, and the United States) and Japan. The measurements are at freestream Mach numbers between 5 and 14, unit Reynolds numbers between 1.5 and , and wall-to-total temperature ratios between 0.1 and 0.8. The study shows that second-mode growth rates can be predicted with parabolized stability equations (PSEs) over the wide range of conditions. The maximum second-mode amplitudes vary weakly at edge Mach number greater than but significantly decrease at lower . The maximum factor envelope from PSE and the measured amplitudes are used to estimate the initial amplitudes . At each Mach number, varies approximately as Reynolds number. This leads to transition factors that increase with Reynolds number. This behavior is consistent with the results from Marineau (“Prediction Methodology for Second-Mode-Dominated Boundary-Layer Transition in Wind Tunnels,” AIAA Journal, Vol. 55, No. 2, 2017, pp. 484–499). This study indicates that amplitude-based methods for second-mode-dominated hypersonic boundary-layer transition predictions should be applicable across a wide range of conditions.