The “sound Of Freedom”: Characterizing Jet Noise From High-Performance Military Aircraft

Gee, Kent L.; Neilsen, Tracianne B.; Wall, Alan T.; Downing, J. Micah; James, Michael M.

doi:10.1121/1.4821141

Cited by 5 publications

(2 citation statements)

References 29 publications

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“…The dominant component of military jet noise is the highly directional, low-frequency radiation from convecting turbulence structures (Viswanathan, 2007;Gee et al, 2013). These structures are formed from instabilities between the higher velocity fluid that exits a nozzle and the lower velocity ambient fluid.…”

Section: Introductionmentioning

confidence: 99%

Cylindrical acoustical holography applied to full-scale jet noise

Wall

Gee

Neilsen

et al. 2014

The Journal of the Acoustical Society of America

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Near-field acoustical holography methods are used to predict sound radiation from an engine installed on a high-performance military fighter aircraft. Cylindrical holography techniques are an efficient approach to measure the large and complex sound fields produced by full-scale jets. It is shown that a ground-based, one-dimensional array of microphones can be used in conjunction with a cylindrical wave function field representation to provide a holographic reconstruction of the radiated sound field at low frequencies. In the current work, partial field decomposition methods and numerical extrapolation of data beyond the boundaries of the hologram aperture are required prior to holographic projection. Predicted jet noise source distributions and directionality are shown for four frequencies between 63 and 250 Hz. It is shown that the source distribution narrows and moves upstream, and that radiation directionality shifts toward the forward direction, with increasing frequency. A double-lobe feature of full-scale jet radiation is also demonstrated.

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Section: Introductionmentioning

confidence: 99%

Cylindrical acoustical holography applied to full-scale jet noise

Wall

Gee

Neilsen

et al. 2014

The Journal of the Acoustical Society of America

Self Cite

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“…Chevrons are the most practical because they can be retrofit to existing variable area nozzles by incorporating them into the diverging sections seals. 38 Though very effective at noise reduction, FI and FEC require delivery of high pressure air to the nozzle exit. Due to this, retrofit applications are highly limited and implementation requires incorporation into designs from the beginning.…”

Section: Figurementioning

confidence: 99%

Supersonic Jet Noise Reduction by Chevrons and Fluidic Injection

Heeb¹,

Kastner²,

Gutmark³

et al. 2013

International Journal of Aeroacoustics

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This work focuses on the noise reduction capabilities of chevrons, fluidic injection, and a combination of both. The control mechanisms were experimentally investigated for over, under, and ideally expanded operating conditions. Acoustic far-field data was collected to quantify noise reductions and changes to the flow field through use of theoretical relations. Results show appreciable noise reduction by both fluidic injection and chevrons. Optimal performance of the two technologies occured at opposite ends of the operation envelope, with the chevrons performing better in the underexpanded regime and the fluidics in the overexpanded regime. The combination of the two technologies was also shown to achieve substantial noise reduction, but direct additive benefits were not always gained. This result is still important as it shows fluidic injection can be employed on complex geometry nozzles, such as that on the F-35, and still achieve noise reduction.

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Acoustic intensity near a high-powered military jet aircraft

Stout

Gee

Neilsen

et al. 2015

The Journal of the Acoustical Society of America

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The spatial variation in vector acoustic intensity has been calculated between 100 and 3000 Hz near a high-performance military aircraft. With one engine of a tethered F-22A Raptor operating at military power, a tetrahedral intensity probe was moved to 27 locations in the geometric near and mid-fields to obtain the frequency-dependent intensity vector field. The angles of the maximum intensity region rotate from aft to sideline with increasing frequency, becoming less directional above 800 Hz. Between 100 and 400 Hz, which are principal radiation frequencies, the ray-traced dominant source region rapidly contracts and moves upstream, approaching nearly constant behavior by 1000 Hz.

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The “sound Of Freedom”: Characterizing Jet Noise From High-Performance Military Aircraft

Cited by 5 publications

References 29 publications

Cylindrical acoustical holography applied to full-scale jet noise

Cylindrical acoustical holography applied to full-scale jet noise

Supersonic Jet Noise Reduction by Chevrons and Fluidic Injection

Acoustic intensity near a high-powered military jet aircraft

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