An experimental analysis of noise generating structures in turbulent jet

Noise-generating structures in turbulent-jet are educed from in-flow velocity and pressure measurements conditioned on far-field acoustic measurements. The anemometric measurements are performed inside a high Re jet flow both on the jet axis and close to the shear layer, for several distances from the nozzle (0 less than or equal tox/D less than or equal to 20) in an anechoic chamber. Experimental data are analyzed through a proper conditional averaging procedure. A triggering method based on the far-field pressure maxima is used to extract events from experimental time series to identify time signatures of velocity and in-flow pressure induced by the coherent structures responsible for the measured far-field noise. The resulting anemometric and acoustic averaged signals are analyzed and discussed in the frame of the properties and topology of the associated coherent structures.