This work aims to study the dynamics of, and noise generated by, the large-scale structures in a Mach 0.9 turbulent jet using simultaneous pressure and velocity measurements alongside plasma-based excitation and advanced analyses to produce either individual or periodic coherent ring-vortices in the shear layer. The dynamics of the large-scale structures were investigated by stochastically-estimating time-resolved velocity fields from planar velocity snapshots and time-resolved near-field pressure traces using a feedforward neural network. Then, using Ribner's dilatation-based acoustic analogy, the aeroacous-tic source terms were computed using the time-resolved velocity field. Results indicated that the ring-vortices underwent a rapid disintegration beginning just upstream of the (time-averaged) end of the potential core; additionally, under certain excitation frequencies merging or multiple merging events of the generated ring-vortices occurred. Analysis of the computed source fields found that the coherent structures produced a convected wavepacket-like event, centered on the jet lipline though reaching into the potential core. Rapid modulation of this wavepacket amplitude and extent occurred in regions of structure merging or disintegration, which resulted in noise emission to the far-field.
展开▼
