“Analysis of Intermittency of Supersonic Jet Noise with Synchronized LES”

Publication Type:
L. Agostini and D. Gaitonde
Year Published:
The effect of turbulent fluctuations on the axis and lip-line of a Mach 1.3 cold jet are analysed with asynchronized pair of Large Eddy Simulations. “Organic” signals are extracted from the first simulation (base-line), processed and injected into a second simulation (twin). The baseline and the twin are then time advancedin a lock step manner. Spectral analysis of the propagated perturbation field of the twin indicates signal di-rectivity induced by the core of the jet. The higher frequencies from the source signal persist in a directionperpendicular to the jet axis from the source location. The intermittency observed in the near field is analysedthrough Short-Time Fourier Transform. The results indicate well-defined wave packets in upstream directionand relatively less coherent wave fronts along aft angles, having longer periods of intermittency. The scalesof fluctuation involved in the wave packets are resolved through Empirical Mode Decomposition and their in-stantaneous frequencies are analysed by obtaining the corresponding Hilbert Spectrum. The Intrinsic ModeFunctions of the signals show evolution of well-defined wave packets from the random turbulent fluctuationsinside the core of the jet. The major component of energy fluctuations in the propagated signal occur betweenSt = 0.2 and St = 1
Conference Name:
21st AIAA/CEAS Aeroacoustics Conference
Conference Location:
Dallas, TX
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Refereed Designation:
Date Published: