Statistical analysis of the pressure field in the near region of a M=0.5 circular jet

In a recent paper [1] a novel technique providing the separation between hydrodynamic and acoustic components of pressure signals has been presented and applied to near field pressure signals measured in a turbulent jet at M = 0.5. The database is further analyzed herein with the scope of clarifying the physical mechanisms underlying the generation of acoustic pressure fluctuations in the near field. The analysis of cross-correlations between pressure and acceleration and the statistics of the potential core fluctuations, confirm that the region at the end of the potential core plays a fundamental role in this sense. A conditional sampling technique based on the use of wavelet transform identifies ensemble averaged velocity traces of the noise sources. The velocity signatures are interpreted as induced by wavepackets, in the region close to the jet exit, and ring vortices in the far region.