Hot-Wire Measurements of Instabilty Waves on Cones at Mach 6

Abstract

Hot wires were used in the Mach-6 tunnel to obtain mass flux profiles and to study the amplitude and growth of instability waves on 7° half-angle sharp and blunt (0.020-inch radius) cones. Measurements were taken at several stagnation pressures (45, 70, 90, and 125 psia) on each of the cones. The boundary layer thickness at convention noise was similar for the sharp and blunt cones, though it was noticed that for the same pressure and axial location the boundary layer on the sharp cone was slightly thinner than that on the blunt cone. The measurements taken with the hot wires were then compared to computations using the STABL code. These comparisons show good agreement both in the shape of the mass flux profiles and the value of mass flux at the edge of the boundary layer. Good agreement was also seen in the frequency of the second-mode instabilities at various pressures; the frequencies found experimentally were within 8% of those calculated by STABL for all cases. Hot wire measurements were also obtained on a sharp cone under quiet-flow conditions and though no instabilities were observed at 0° angle of attack, when placed at a 3° angle of attack, peaks in the spectra were observed at 130 kHz which could be attributed to instabilities.