Flow-field analysis of subsonic jets at Mach 0.5 and 0.84 using 3D Multi-Pulse STB

A subsonic air jet flow in air at Mach 0.506 and 0.845 generated by a round as well as a chevron nozzle with an inner diameter D j of 15mm is investigated using three-dimensional Lagrangian Particle Tracking and simultaneous far field microphone measurements. The Shake-The-Box (STB) method allows highly spatially resolved accurate velocity and acceleration measurements to be recovered at high particle densities when compared to a Particle Image Velocimetry (PIV) reference dataset. The high resolution is possible because of bin averaging the large amount of available snapshots and enables resolving extremely steep velocity gradients in the shear layer of the jet close to the nozzle. Mean velocity, acceleration and velocity fluctuation profiles as close as a distance of 0.2 D j to the nozzle exit are presented. The density of recovered particles is sufficient for analysis of instantaneous tracks, velocity vector volumes, coherent structures, and evaluation of the velocity gradient tensor. Results are shown in terms of instantaneous visualizations of the flow-field in addition to the ensemble averaged statistics.