Quantitative Hot-Wire Measurements in Supersonic Boundary Layers

Mean and time-resolved measurements in a supersonic boundary layer were performed in the Mach 3.5 quiet tunnel facility at the NASA Langley Research Center. This facility uses an annular bleed suction system to remove the turbulent boundary layer, thus reducing the disturbance intensities in the measurement region. A frequency-compensatedconstant current hot-wire anemometer was used to obtain fluctuation data in the boundary layer of a sharp cone at zero angle of attack. The hotwire was calibrated against the mean mass-flux profiles provided by solutions of the similarity profiles for compressible Blasius flow. A stability analysis code provided by Langley was used to solve parabolized stability equations to provide predictions of the most amplified wave-numbers, frequencies, and N-factors for the Tollmien-Schlicting instability. The results from these computations are compared to the experimental measurements performed with the anemometer. In addition, these measurements are compared to spectra obtained in high-disturbance conditions with the bleed system turned off.