Structure of coherent instabilities in a supersonic shear layer

Abstract

Detailed measurements have been made of the instabilities present in supersonic shear layers. A high-speed stream of Mach number 3 or 4 and a low-speed stream of Mach number 1.2 are produced and begin mixing at the trailing edge of the dividing centerbody. Glow discharge excitation is used to excite either two-dimensional or oblique instability waves. Mach-number profiles for the Mach 3 case show little effect of excitation on the growth rate, whereas the higher Mach number case shows enhanced mixing with both exaltation geometries. Four hot wires are used simultaneously to measure the axial and spanwise wavelengths for each case. With these wavelengths, the propagation angles of the instabilities are calculated.