Intermittent statistics and stochastic modelling of low and high Re compressible jets

Abstract

In this work, we studied the intermittent statistics of pressure fluctuations in the near field of compressible subsonic single stream jets. The analysis has been performed considering data from numerical simulations of two isothermal jets having the same Mach number, M=0.9, and two different Reynolds number (3,125 and 100,000). Pressure fluctuations were measured by virtual probes located in different positions in the radial and axial directions. Intermittent events are extracted through appropriate wavelet-based indicators and two random variables are analyzed, namely the intermittent time Δ, that is the time delay between two successive events, and the energy amplitude A. Their statistics are computed with the scope of adressing the stochastic model proposed by Camussi et al. [1] that was settled up on the basis of experimental data. The present analysis extends the validity of the model to very low Reynolds number conditions and to the statistics of the 0ℎ azimuthal mode of the pressure fluctuations that exhibit a relevant degree of intermittency around the Kelvin-Helmholtz frequency.