\The low frequency sound from multipole sources in axisymmetric shear ows, with applications to jet noise," J. ow with a uniform mean temperature gradient," J. \On the two components of turbulent mixing noise from supersonic jets," AIAA paper 96

This study explores an alternative approach using a semi-empirical equivalent simple-source model to analyze and characterize the turbulence-induced aeroacoustic sources from military jet aircraft. Initially the model is a single point source located above a hard plane such that the locations of destructive interference from its mirror image matched the measured interference nulls. This provide...

Background: There is a growing need to reduce significantly the noise generated by high-performance, supersonic military aircraft. The noise generated during takeoff and landing on aircraft carriers has direct impact on shipboard health and safety issues. Also, noise complaints are increasing as communities move closer to military bases or when there are changes due to base closures and realign...

Chevron mixing devices are used to reduce noise from commercial separate-flow turbofan engines. Mechanical chevron serrations at the nozzle trailing edge generate axial vorticity that enhances jet plume mixing and consequently reduces far-field noise. “Fluidic chevrons” generated with air injected near the nozzle trailing edge create a vorticity field similar to that of the mechanical chevrons ...

Gudmundsson and Colonius (J. Fluid Mech., vol. 689, 2011, pp. 97–128) have recently shown that the average evolution of low-frequency, low-azimuthal modal large-scale structures in the near field of subsonic jets are remarkably well predicted as linear instability waves of the turbulent mean flow using parabolized stability equations. In this work, we extend this modelling technique to an isoth...

Bicoherence analysis has been used to characterize nonlinear effects in the propagation of noise from a model-scale, Mach-2.0, unheated jet. Nonlinear propagation effects are predominantly limited to regions near the peak directivity angle for this jet source and propagation range. The analysis also examines the practice of identifying nonlinear propagation by comparing spectra measured at two ...

Meaningful use of the autocorrelation in jet noise analysis is examined. The effect of peak frequency on the autocorrelation function width is removed through a temporal scaling prior to making comparisons between measurements or drawing conclusions about source characteristics. In addition, a Hilbert transform-based autocorrelation envelope helps to define consistent characteristic time scales...