Pressure conditioning for coherent structures identification in a turbulent jet

A method is presented for the use of far-field acoustic measurements as a trigger for the conditional averaging of velocity signals taken from inside a jet flow. The triggering procedure is applied to experimental data taken in a jet flow in the anechoic chamber of ISPESL (laboratory of “Agenti Fisici”) where simultaneous acoustic and anemometric measurements were performed. Data are then analyzed through two post-processing techniques, a “direct” and a “wavelet” method. The achieved averaged signals are time signatures of the generating noise coherent structures whose properties and topology are analyzed and discussed as functions of the distance from the nozzle.