Experiments have characterized the acoustics of axisymmetric high-speed jets at a variety of Mach numbers and velocities and at pressure-matched, overexpanded, and underexpanded conditions. The effect of an annular secondary  ow on noise emission was also investigated.The fully expanded jet velocity ranged from 630 to 920m/s and the fully expanded jet Mach number ranged from 1.27 to 1.75.The s...

Broadband, partially correlated noise radiated from supersonic jets has characteristics that scale with nozzle size and flow properties. In particular, the spectral content of jet noise and variation with angle in many cases agree with empirically derived similarity spectra for large and fine-scale components of turbulent mixing noise [Tam et al., AIAA paper 96-1716]. In previous studies, measu...

The mixing noise in jet engine exhaust is one of the main noise sources in aviation. Nozzle lip serrations, commonly called chevrons, are one of the technologies deployed to address the issue in modern civilian aircraft. These nozzle serrations impinge on the shear layer and change its dynamics; the jet plume becomes lobed or serrated near the nozzle in a time-averaged sense, but reverts to a r...

Supersonic commercial aircraft noise predictions have frequently considered only exhaust noise from the jet engines. Meeting the stringent noise requirements that apply to the subsonic fleet will require reducing jet exhaust noise to the point that fan noise may also require reduction. This report discusses the prediction of fan noise for a supersonic commercial aircraft using existing empirica...

PO 107‐1 Design, Development and Evaluation of a Noise Control Enclosure for a Model Jet Engine J. Black, J. Rinker, R. Yon, C. Holder, U.S. Air Force, Wright‐Patterson AFB, OH; J. Slagley, School of Aerospace Medicine, Wright‐ Patterson AFB, OH. Situation/problem: A cart‐mounted model jet engine used for educational demonstrations produced a sound pressure level (SPL) of 89.1 dB at a distance...

Published near-field analyses of full-scale jet noise are limited, and the application of observed laboratory scale phenomena to full-scale jets is not well understood. To obtain a greater understanding of the connection between radiated noise and source characteristics in full-scale, heated, supersonic jets produced by military aircraft, acoustical measurements were made in the geometric near ...

A new algorithm for estimating noncompact, distributed sources by means of phased array microphone measurements is presented and experimentally implemented to determine the noise source distribution in a subscale jet  ow. Conventional beamforming techniques, developed for spatially well-separated point sources, can lead to signiŽ cant errors when applied to reconstruct continuous source distri...

Jet noise reduction remains an important long-range goal in commercial and military aviation. Comparedwith their early counterparts, modern, ultrahigh-bypass-ratio turbofans on commercial aircraft are very quiet, but evermore stringent noise regulations dictate further reductions. In addition, hearing loss bypersonnel and community noise issues are prompting the military to seek noise reduction...

A temporally-developing isothermal round jet at a Mach number of 0.9 and a diameterbased Reynolds number of 3125 is computed by direct numerical simulations in order to investigate its turbulent development and its generated noise. The simulations are performed using high-order finite differences on a grid of 940 million points extending up to 120 jet radii in the axial direction. Snapshots and...