High-speed schlieren visualizations are used to study second-mode instability development within the boundary layer of a 7° half-angle sharp cone at Mach 10 and Mach 14. Unit Reynolds numbers range from 1.62 to 7.19×10~6 m~(-1). The visualizations are used to extract time-resolved and ensemble-averaged quantitative data on second-mode instability waves in the transitional phase. A method for converting spatial data to temporal data is applied to the images to examine disturbance intensities at specific cone locations over finite time intervals. For the Mach 14 data, a lens calibration enables the calculation of spatial amplification rates. Comparison of experimentally computed jV factors with linear stability theory shows good agreement for the most amplified frequencies. Spatially developing N factors calculated from schlieren image data also compare favorably to those calculated from PCB pressure sensors with slight variations of the harmonic frequencies. The relation between the two measurement techniques is examined by analyzing the pressure measurements of a spanwise PCB array and schlieren images captured at the same location and instant in time. The evolution of individual wavepackets is also analyzed throughout the transition process.
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