A 3D Prediction of the Wing Reflection of Aero Engine Noise

Moore, Alastair

doi:10.2514/6.2004-2865

Cited by 14 publications

(12 citation statements)

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“…In conjunction with the above experimental and numerical studies of installed jet noise characteristics, attempts to develop prediction models for installed jet noise have also been made. These include the work by Stevens et al (1983), Sengupta (1983), Moore (2004) and Bhat & Blackner (1998). With the exception of Moore's model, which is based on 3D ray theory and jet blockage profiles and gives encouraging results at high frequencies, the prediction models proposed at this time were generally empirical, i.e.…”

Section: Introductionmentioning

confidence: 99%

Prediction of installed jet noise

2016

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A semi-analytical model for installed jet noise is proposed in this paper. We argue and conclude that there exist two distinct sound source mechanisms for installed jet noise and the model is therefore composed of two parts to account for these different sound source mechanisms. Lighthill's acoustic analogy and a fourth-order space-time correlation model for Lighthill stress tensor are used to model the sound induced by the equivalent turbulent quadrupole sources, while the trailing-edge scattering of near-field evanescent instability waves are modelled using Amiet's approach. A non-zero ambient mean flow is taken into account. It is found that, when the rigid surface is not so close to the jet as to affect the turbulent flow field, the trailing-edge scattering of near-field evanescent waves dominates the low frequency amplification of installed jet noise in the far-field. The high-frequency noise enhancement on the reflected side is due to the surface reflection effect. The model agrees well with experimental results at different observer angles apart from deviations caused by mean-flow refraction effect at high frequencies at low observer angles.

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Section: Introductionmentioning

confidence: 99%

Prediction of installed jet noise

2016

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“…However, for high-subsonic and supersonic flows the diffusion coefficient, D on the right-hand side becomes small or even non-positive, which slows down the iterative convergence. Then for the actual numerical solution (10) is replaced by (11)…”

Section: B Numerical Solution Methodsmentioning

confidence: 99%

“…Since existing optimised program elements are used for solving the convectiondiffusion problem, the solution approach is readily implementable and parallelizable. Equations (11) and (4) need to be solved together in an iterative loop. Hence, an initial guess to φ is needed prior to this loop.…”

Section: B Numerical Solution Methodsmentioning

confidence: 99%

“…Apart from the theoretical studies, the eikonal equation can be a valuable engineering tool in the context of studying acoustic shielding designs. For example, with aircraft, the engines can be located so that the airframe shields observer noise, thus reducing environmental impact (see Agarwal [9], Moore and Mead [10] and Moore [11]). In most of the studies in the literature, either too simplistic geometries are considered or the meanflow effect on sound refraction is completely ignored.…”

Section: Introductionmentioning

confidence: 99%

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Unstructured Grid Solution of the Eikonal Equation for Acoustics

Tucker

Karabasov

2009

International Journal of Aeroacoustics

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An acoustic eikonal equation solution procedure, that is easy to implement in unstructured grid Navier-Stokes equation flow solvers, is outlined. The approach is readily parallelizable. The method is tested for the following canonical point source cases: quiescent flow; subsonic uniform flow; supersonic uniform flow and an idealized jet flow. Then, as further validation, sound propagation of a wave front through a viscous vortex is considered. For these cases, encouraging agreement is found with analytic data and a high-fidelity numerical solution of the Euler equations. Finally, as demonstration cases, the use of the approach to study the shielding of noise from a planar jet is considered along with wave propagation in a complex three-dimensional geometry. At lower Mach numbers (< 0.25), for complex geometries, robust multigrid convergence acceleration is found.

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“…Due to the urgency of further reducing aircraft noise, jet-wing interaction noise has gained much attention in the research community in recent years (Mead & Strange 1998;Pastouchenko & Tam 2007;Bondarenko et al 2012;Brown 2013;Semiletov et al 2016;Bhat & Blackner 1998;Moore 2004;Vera et al 2015;Cavalieri et al 2014;Piantanida et al 2016;Lyu & Dowling 2016;. Recent work shows that the scattering of wave-packets can be used to model installed jet noise around peak frequencies.…”

Section: Introductionmentioning

confidence: 99%

Modelling installed jet noise due to the scattering of jet instability waves by swept wings

Lyu

Dowling

2019

J. Fluid Mech.

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Jet noise is a significant contributor to aircraft noise, and on modern aircraft it is considerably enhanced at low frequencies by a closely installed wing. Recent research has shown that this noise increase is due to the scattering of jet instability waves by the trailing edge of the wing. Experimentalists have recently shown that noise can be reduced by using wings with swept trailing edges. To understand this mechanism, in this paper, we develop an analytical model to predict the installed jet noise due to the scattering of instability waves by a swept wing. The model is based on the Schwarzschild method and Amiet’s approach is used to obtain the far-field sound. The model can correctly predict both the reduction in installed jet noise and the change to directivity patterns observed in experiments due to the use of swept wings. The agreement between the model and experiment is very good, especially for the directivity at large azimuthal angles. It is found that the principal physical mechanism of sound reduction is due to destructive interference. It is concluded that in order to obtain an effective noise reduction, both the span and the sweep angle of the wing have to be large. Such a model can greatly aid in the design of quieter swept wings and the physical mechanism identified can provide significant insight into developing other innovative noise-reduction strategies.

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A 3D Prediction of the Wing Reflection of Aero Engine Noise

Cited by 14 publications

References 1 publication

Prediction of installed jet noise

Prediction of installed jet noise

Unstructured Grid Solution of the Eikonal Equation for Acoustics

Modelling installed jet noise due to the scattering of jet instability waves by swept wings

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