Using Wavelet transforms and Linear Stochastic Estimation to study nearfield pressure and turbulent velocity signatures in free jets

Abstract

A data post-processing technique (denoted as WLSE) based on the combination of wavelet transforms with the Linear Stochastic Estimation (LSE) method is applied to pressure and velocity signals obtained in an isothermal subsonic co-axial jet. The aim of the method is to identify and clarify the role of intermittent turbulent events in the generation of nearfield pressure fluctuations. To this purpose, a wavelet-based filtering procedure is performed to extract intermittent events from the pressure signals and the LSE technique is applied to identify velocity fluctuations which are linearly associated with the selected pressure fluctuations. The methodology comprises two main steps: (i) Pressure signal filtering using the wavelet transform and decomposition of the given signal into intermittent and non-intermittent components; (ii) Reconstruction using LSE of velocity fluctuations linearly associated with the wavelet-filtered part of the pressure signals. Preliminary results, showing encouraging outcomes, are presented and discussed.