Coherent large-scale structures in high Reynolds number supersonic jet of Mach number 1.4

Large-scale coherent structures are found to exist in fully expanded shock free supersonic jets with Reynolds number 1.6 million and Mach number 1.4. The jet was excited by a weak upstream tone to extract the large-scale structures from the random turbulence. The most preferential excitation Strouhal number is found to be in the vicinity of 0.4, and the dependence of the large-scale structure phase velocity on the excitation Strouhal number shows a similar trend to that found for subsonic acoustically excited jets.