Comparison of Experimentally Measured and Computed Second-Mode Disturbances in Hypersonic Boundary-Layers

Abstract

Abstract : Experiments were carried out in the Boeing/AFOSR Mach 6 Quiet Tunnel at Purdue University and the Sandia National Laboratories Hypersonic Wind Tunnel at Mach 5 and 8. The purpose was to measure second-mode boundary-layer instabilities on a 7 deg half-angle cone at zero angle of attack using surface pressure sensors. Second-mode waves were successfully measured at all three Mach numbers, including under both noisy and quiet conditions. The most amplified second-mode disturbance frequencies compared well to the linear Parabolized Stability Equations computed by the STABL software suite. The eigenfunctions are also reported, to aid in the development of new instrumentation methods. The e(expn N) method is used in an attempt to determine the N factor for transition onset prediction in both tunnels.