Comparison of near-field events and their far-field acoustic signatures in experimental and numerical high speed jets

Two different approaches are applied to near-field (NF) velocity field and far-field (FF) pressure signals to gain better understanding of the flow structures that contribute to high speed jet noise. We use laboratory data from a 10kHz TRPIV experiment data of Mach 0.6 jet and numerical data from an 80kHz LES database at Mach 0.9 jet. From the NF, over 20 representative diagnostics are extracted as time traces, of which about half give high correlation with the far-field. Utilizing cross-correlation and wavelet analysis, we locate the frequency band where information is transferred from NF to FF. Furthermore we identify excerpts in time and frequency domain that act as major correlation contributors. The lists of events based on FF only (acoustic footprints) and on NF-FF correlations are compared and show good similarity, which validates both techniques. Finally, the lists of events are separated into categories based on their properties, including magnitude, frequency, and time of occurrence.