Dominant aeroacoustic source contribution in a hot transonic jet

The near-field region of a Mach 0.6 axisymmetric jet, T_r=1.72 and exit nozzle diameter of 50.8mm, is examined experimentally with the aim of characterizing the dominant aeroacoustic sources. PIV measurements are acquired at downstream locations subsequent to the collapse of the potential core region, where acoustic sources have shown to exhibit the strongest contribution to the far-field noise. The fluctuating pressure field is simultaneously sampled at 2D downstream of the jet exit, within the hydrodynamic region, by an azimuthal array of 15 transducers. Application of a low-dimensional technique, combines the discretely sampled velocity field with the temporally resolved pressure measurements to reconstruct an estimate of the 'large-scale' velocity field. Six far-field microphones positioned on an arc at 75D from the jet centerline serve as a measure of direct comparison, as correlations with the low-dimensional, estimated velocity field illustrate the spatial and temporal extent of noise producing events. This study comprises two temperature ratios, T_r= 1 and T_r = 1.72 in an effort to validate this approach, isolating the effect of temperature, as noise sources are known to be altered at elevated temperatures.