View Video Presentation: https://doi.org/10.2514/6.2022-1825.vid

The boundary layer on a sharp-tip, partially flared, actively cooled cone has been studied in a quiet Mach 6 wind tunnel using Focused Laser Differential Interferometry (FLDI). The most dominant cause of boundary-layer transition for Mach numbers greater than 4 is the second-mode instability, which is being analyzed here. The conditions were varied by changing the Reynolds number of the flow and setting the wall temperature to two conditions. The spectral content showed the presence of the second-mode instability and two of its harmonics across the Reynolds number sweep. A novel analysis of FLDI data is presented which show how the cooler wall condition transitions to turbulence sooner. This analysis may also be of benefit for defining a transition location or region from FLDI data in general.