Effects of artificial excitation upon a low Reynolds number Mach 2.5 jet

The effects of a single point glow discharge excitation device upon a low Reynolds number (8700), Mach 2.5, axisymmetric, cold air jet were experimentally investigated. Both the acoustic and flow fields of the jet were altered by the excitation; the acoustic field could be altered to a greater extent, however, by the addition of a spurious lobe to the sound pressure level contours. It was also possible to reduce the level of excitation so that the acoustic field showed only a slight decrease in the amplitude of the noise radiated by the jet. The main effect of low level excitation was a slight compacting of the development of the jet into a shorter axial length. A decrease in the broadband turbulence, a narrowing of the breadth of the peak in the spectrum around the fundamental frequency, and an enhancement of the harmonics were also