Novel chevron nozzle concepts for jet noise reduction

Tide, P. S.; Srinivasan, K.

doi:10.1243/09544100jaero347

Cited by 14 publications

(13 citation statements)

References 18 publications

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“…To investigate the effect of the chevron profile (curvature along the azimuthal direction) on the far-field noise, Tide and Srinivasan [5] have performed experiments on various chevron nozzles for a wide range of Mach numbers. They compared the sinusoidal profile chevron nozzle with the conventional chevron nozzle, which has a linear profile.…”

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confidence: 99%

Acoustic Sources and Far-Field Noise of Chevron and Round Jets

et al. 2015

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This paper investigates numerically the acoustic sources and far-field noise of chevron and round jets. The acoustic sources are described by the fourth-order space-time velocity cross correlations, which are calculated based on a large-eddy simulation flowfield. Gaussian functions are found to fit the axial, radial, and azimuthal cross correlations reasonably well. The axial length scales are three to four times the radial and azimuthal length scales. For the chevron jet, the cross-correlation scales vary with azimuthal angle up to six jet diameters downstream; beyond that, they become axisymmetric like those for a round jet. The fourth-order space-time cross correlation of the axial velocity R 1111 is the dominant source component, and there are considerable contributions from other source components such as R 2222 , R 3333 , R 1212 , R 1313 , and R 2323 cross correlations where 1, 2, and 3 represent axial, radial, and azimuthal directions, respectively. For the chevron jet, these cross correlations decay rapidly with axial distance whereas for the round jet, they remain roughly constant over the first 10 jet diameters. The chevron jet intensifies both the R 2222 and R 3333 cross correlations within two jet diameters of the jet exit. The amplitude, length, and time scales of the crosscorrelations of a large-eddy simulation velocity field are investigated as functions of position and are found to be proportional to the turbulence amplitude, length, and time scales that are determined from a Reynolds-averaged Navier-Stokes calculation. The constants of proportionality are found to be independent of position within the jet, and they are quite close for chevron and round jets. The scales derived from Reynolds-averaged Navier-Stokes are used for source description, and an acoustic analogy is used for sound propagation. There is an excellent agreement between the far-field noise predictions and measurements. At low frequencies, the chevron nozzle significantly reduces the far-field noise by 5-6 dB at 30 deg and 2-3 dB at 90 deg to the jet axis. However, the chevron nozzle slightly increases high-frequency noise. It was found that R 1212 and R 1313 cross correlations have the largest contribution to the jet noise at 30 deg to the jet axis, whereas the R 2323 cross correlation has the largest contribution to the jet noise at 90 deg to the jet axis. The Reynolds-averaged Navier-Stokes calculations are repeated with different turbulence models, and the noise prediction is found to be almost insensitive to the turbulence model. The results indicate that the modeling approach is capable of assessing advanced noise-reduction concepts.

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confidence: 99%

Acoustic Sources and Far-Field Noise of Chevron and Round Jets

et al. 2015

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“…Drastic modification of the jet cross-section was achieved by the investigated configurations, with both elliptic and triangular shapes attained downstream. Consequently, screech was nearly eliminated with reductions in the range of [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] dB depending on the operating condition. Analysis of the streamwise velocity indicated that both the mean shock spacing and strength were reduced resulting in an increase in the broadband shock associated noise spectral peak frequency and a reduction in the amplitude, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…For example, of the above mentioned studies, Seiner et al [1] was the only group which did not employ 12 chevrons and only a single chevron configuration was investigated. Arrangement has been investigated in the past for chevrons applied to non-military style nozzles in both subsonic [9], and supersonic [10][11][12] jets. Bridges and Brown [9] found that periodic azimuthally spaced chevrons with asymmetric geometry were detrimental to subsonic noise reduction when compared to chevrons with symmetric geometry and identical penetration.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, due to a lack of azimuthal periodicity, an azimuthal sound field was measured which required operating condition dependent clocking (relative to the engine's pylon) for optimal noise reduction. Finally, Tide and Srinivasan [11,12] investigated the effect of chevron number and asymmetry on sonic nozzles. They found that increases in chevron number were beneficial, and chevron asymmetries improved noise reduction, in particular broadband shock associated noise (BSAN), compared to standard chevron configurations at specific azimuthal angles.…”

Section: Introductionmentioning

confidence: 99%

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Impact of chevron spacing and asymmetric distribution on supersonic jet acoustics and flow

Heeb

Gutmark

Kailasanath

2016

Journal of Sound and Vibration

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“…Furthermore, examination of the relationships between chevron geometric parameters and flow characteristics was performed. Tide and Srinivasan [19] proposed two novel chevron concepts and evaluates their noise reduction performance. The new chevron concepts proposed were protrusions with a sinusoidal profile and chevrons with asymmetry.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on Aerodynamic and Combustion Performance of Chevron Mixer Inside an Afterburner

Shan

Zhang

Yameng

2014

Journal of Engineering for Gas Turbines and Power

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To improve the performance of the afterburner for the turbofan engine, an innovative type of mixer, namely, the chevron mixer, was considered to enhance the mixture between the core flow and the bypass flow. Computational fluid dynamics (CFD) simulations investigated the aerodynamic performances and combustion characteristics of the chevron mixer inside a typical afterburner. Three types of mixer, namely, CC (chevrons tilted into core flow), CB (chevrons tilted into bypass flow), and CA (chevrons tilted into core flow and bypass flow alternately), respectively, were studied on the aerodynamic performances of mixing process. The chevrons arrangement has significant effect on the mixing characteristics and the CA mode seems to be advantageous for the generation of the stronger streamwise vortices with lower aerodynamic loss. Further investigations on combustion characteristics for CA mode were performed. Calculation results reveal that the local temperature distribution at the leading edge section of flame holder is improved under the action of streamwise vortices shedding from chevron mixers. Consequently, the combustion efficiency increased by 3.5% compared with confluent mixer under the same fuel supply scheme.

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Novel chevron nozzle concepts for jet noise reduction

Cited by 14 publications

References 18 publications

Acoustic Sources and Far-Field Noise of Chevron and Round Jets

Acoustic Sources and Far-Field Noise of Chevron and Round Jets

Impact of chevron spacing and asymmetric distribution on supersonic jet acoustics and flow

Numerical Investigation on Aerodynamic and Combustion Performance of Chevron Mixer Inside an Afterburner

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