Exhaust noise in flight - The role of acoustic installation effects

Southern, I. S.

doi:10.2514/6.1980-1045

Cited by 11 publications

(11 citation statements)

References 6 publications

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“…4, since our numerical experiments indicated it had a small impact. The reason why this is the case is clear if we carry out the derivatives in (15)…”

Section: Sensitivity Of Model To Parameters (A 1 a 2 )mentioning

confidence: 99%

“…7). We, therefore, use the function based on the model in [38]): (15) where coefficients, a n = (a 0 ,a 1 ,a 2 ) , are empirical parameters and the decay function multiplying the square brackets is defined by exponent,…”

Section: Modeling De--correlation Effects In ρ ′mentioning

confidence: 99%

“…(20) and α = 0 in Eqs. (15) & (16). The impact of these spectral differences on the edge noise spectrum is discussed in the next section.…”

Section: Jet--surface Interaction Acoustic Spectrum Formula With a Fimentioning

confidence: 99%

“…We These results show that the acoustic spectrum is now directly dependent on how fast the turbulence de--correlates in Eq. (15). In its absence (i.e.…”

Section: Acoustic Spectrum With a Purely Dipole--like Frequency Scamentioning

confidence: 99%

“…19) and also more recent references [16]-- [18]. Even though much of past, and some of the recent, investigations have been performed on round jets interacting with trailing edges ( [11], [15]---- [18]), Head & Fisher [12] noted that the observed results of noise amplification and trends with various jet parameters were similar to those produced by a large aspect ratio rectangular nozzle.…”

mentioning

confidence: 92%

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Effect of de-correlating turbulence on the low frequency decay of jet-surface interaction noise in sub-sonic unheated air jets using a CFD-based approach

Afsar

Leib

Bozak

2017

Journal of Sound and Vibration

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In this paper we extend the Rapid-distortion theory (RDT)-based model derived by Goldstein, Afsar & Leib (J. Fluid Mech., vol. 736, pp. 532-569, 2013) for the sound generated by the interaction of a large-aspect-ratio rectangular jet with the trailing edge of a flat plate to include a more realistic upstream turbulence spectrum that possess a de-correlation (i.e. negative dip) in its space-time structure and use results from three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions to determine the mean flow, turbulent kinetic energy and turbulence length & time scales. Since the interaction noise dominates the low-frequency portion of the spectrum, we use an appropriate asymptotic approximation for the Rayleigh equation Green’s function, which enters the analysis, based on a two-dimensional mean flow representation for the jet. We use the model to predict jet-surface interaction noise for a range of subsonic acoustic Mach number jets, nozzle aspect ratios, streamwise and transverse trailing-edge locations and compare them with experimental data. The RANS meanflow computations are also compared with flow data for selected cases to assess their validity. We find that finite de-correlation in the turbulence spectrum increases the low-frequency algebraic decay (the low-frequency “roll-off”) of the acoustic spectrum with angular frequency to give a model that has a pure dipole frequency scaling. This gives better agreement with noise data compared to Goldstein et al. (2013) for Strouhal numbers less than the peak jet-surface interaction noise. For example, through sensitivity analysis we find that there is a difference of 10 dB at the lowest frequency for which data exists (relative to a model without de-correlation effects included) for the highest acoustic Mach number case. Secondly, our results for the planar flow theory provide a first estimate of the low-frequency amplification due to the jet-surface interaction for moderate aspect ratio nozzles when RANS meanflow quantities are used appropriately. This work will hopefully add to noise prediction efforts for aircraft configurations in which the exhaust systems are tightly integrated with the airframe

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“…4, since our numerical experiments indicated it had a small impact. The reason why this is the case is clear if we carry out the derivatives in (15)…”

Section: Sensitivity Of Model To Parameters (A 1 a 2 )mentioning

confidence: 99%

Section: Modeling De--correlation Effects In ρ ′mentioning

confidence: 99%

“…(20) and α = 0 in Eqs. (15) & (16). The impact of these spectral differences on the edge noise spectrum is discussed in the next section.…”

Section: Jet--surface Interaction Acoustic Spectrum Formula With a Fimentioning

confidence: 99%

“…We These results show that the acoustic spectrum is now directly dependent on how fast the turbulence de--correlates in Eq. (15). In its absence (i.e.…”

Section: Acoustic Spectrum With a Purely Dipole--like Frequency Scamentioning

confidence: 99%

mentioning

confidence: 92%

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Effect of de-correlating turbulence on the low frequency decay of jet-surface interaction noise in sub-sonic unheated air jets using a CFD-based approach

Afsar

Leib

Bozak

2017

Journal of Sound and Vibration

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Wavepacket Modelling of Jet-Flap Interaction Noise: from Laboratory to Full-Scale Aircraft

Huber,

Pont,

Jordan

et al. 2024

Flow Turbulence Combust

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Numerical study of jet-plate interaction and its effects on aeroacoustics

Wang,

Lai

2024

J. Phys.: Conf. Ser.

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In modern under-wing-mounted high-bypass engines, the exhausted jet from the engine will interact strongly with the wing and high-lift devices. In this paper, simulations of an isothermal jet flow at Mach number Ma = 0.5 and close to a flat plate are carried out using large-eddy simulation. Far-field acoustic results are obtained via the surface integral method of Ffowcs Williams and Hawkings (FW-H). The studied cases include an isolated jet and other three configurations with the jet and a plate spaced at the distance H/D j = 1.0, 1.5, and 2.0, respectively, from the jet axis. Validation against experimental data is carried out. Far-field acoustic results show that the overall noise levels are significantly increased for the installed cases, particularly for polar angles in upstream of the nozzle. The noise levels are increased more as the plate approaches the jet axis, indicating the installation effect is related to the H/D and the polar angle. The pressure fluctuations are shown to decay along the radial direction. The mean flow and power spectral density of the axial velocity show the characteristics of the jet flow is not significantly changed by the presence of the plate.

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Exhaust noise in flight - The role of acoustic installation effects

Cited by 11 publications

References 6 publications

Effect of de-correlating turbulence on the low frequency decay of jet-surface interaction noise in sub-sonic unheated air jets using a CFD-based approach

Effect of de-correlating turbulence on the low frequency decay of jet-surface interaction noise in sub-sonic unheated air jets using a CFD-based approach

Wavepacket Modelling of Jet-Flap Interaction Noise: from Laboratory to Full-Scale Aircraft

Numerical study of jet-plate interaction and its effects on aeroacoustics

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