Fine structure of the flow of a supersonic underexpanded turbulent jet

A pulsed laser technique was used to determine the magnitude and region of turbulent pulsations of density in a supersonic underexpanded jet. The data indicate the existence of a complex fine structure. An analysis of measurements at the initial section of the jet demonstrate that density pulsations are absent in the jet core and directly behind the Mach disk, but arise in the mixing layer in the region with a maximum density gradient. Results are presented for a Reynolds number (suitably defined for the initial section) of 10,000.