SUBSONIC jet noise has been a hot topic in the last 50 years because of its relevance in the design of modern civil aircraft tackling the problem of minimizing the noise impact. Since the publication of the Lighthill’s famous paper [1], many researchers investigated jet-induced pressure fluctuations both in the near field and in the far field in the attempt of developing models able to predict as accurately as possible the emitted noise. There is a large body of literature that seeks to clarify the nature of pressure events that dominate both fields. The pressure fluctuations in the near field are influenced by vortical structures generated in the jet shear layer (see [2, 3] and the recent paper by Adam et al.[4]), and, according to the typical statistics of vorticity in turbulence, they exhibit a non-Gaussian intermittent behavior. In a statistical sense, intermittency is intended as a sequence of quiescent phases interrupted by active events inducing a nonstationary distribution of energy in time. As shown by the seminal experiment undertaken by Juvé et al.[5] and by numerous successive studies (eg,[6–11]), intermittency is a key mechanism in the generation of jet noise and, as shown by several recent papers (see, among many,[12–14]), the related turbulence nonlinearities are recognized to play a relevant role in the acoustic radiation (see also [15, 16]).

The results reported by Kearney-Fischer et al.[17] and Kearney-Fischer [18] further support the idea that intermittent events are the dominant feature of jet noise. They applied a method to extract the events and developed stochastic models to reproduce their statistics in both the physical and the Fourier domains. A similar approach was adopted by Camussi et al.[19, 20], who used wavelet transform to select intermittent events from experimental data and proposed stochastic models to reproduce their relevant statistics. These analyses provided a direct measure of the degree of intermittency contained in the pressure field induced by compressible jets. The main objective of the present work is to assess and validate the model proposed in [19, 20] by processing a pressure database obtained numerically. The experimental data analyzed in [19, 20] consisted of pressure fluctuations measured through a single linear array in the near field of a compressible jet for Mach number spanning from 0.5 to 0.9 at a single high Reynolds number (of the order of 105). The numerical database analyzed therein provides pressure in a very large number of axial and radial positions in the near field, allows for the analysis of different Reynolds numbers at the same high subsonic Mach number, and includes the zero-order axisymmetric mode, extracted through a Fourier azimuthal decomposition of the pressure signals. The paper in [21] analyzes the same numerical database as the present one through the computation of a time-frequency version of the flatness factor, a procedure that, as will be clarified below, is different with respect to the one used in the present paper that replicates the approach adopted in [19, 20]. The present paper therefore represents a definite validation of the stochastic models proposed in [19, 20], extending them to a broader range of flow conditions and to the statistics of the zero-order axisymmetric mode, which is of specific relevance because of its relationship with the jet noise. The paper is organized as follows: Sec. II reports the numerical setup and the postprocessing procedure, results are discussed in Sec. III, and final remarks are presented in Sec. IV.