Instantaneous supersonic velocity profiles in an underexpanded sonic air jet by oxygen flow tagging

Abstract

The statistics and structure of velocity profiles across the free shear layer of a sonic free jet are examined using oxygen tagging by Raman excitation plus laser-induced electronic fluorescence. The flow is observed both before and after the Mach disk at centerline Mach numbers of 3.6 and 0.4, respectively. Instantaneous images of the displaced line of tagged molecules show a clear picture of the turbulent structure including large-scale coherent features.