Experimental validation of the hybrid scattering model of installed jet noise

Lyu, Benshuai; Dowling, Ann P.

doi:10.1063/1.5036951

Cited by 12 publications

(10 citation statements)

References 33 publications

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“…Suffice to mention here that although the Reynolds number in Tanna's study is twice as large as that used in our study, the agreement between the two is good enough to show that the measurement is reliable. Details of this validation can be found in Lyu and Dowling (2018a). In what follows, we will start by showing the results for isolated jet noise.…”

Section: Resultsmentioning

confidence: 99%

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An experimental study of the effects of lobed nozzles on installed jet noise

Lyu

Dowling

2019

Exp Fluids

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Jet noise remains a significant aircraft noise contributor, and for modern high-bypass-ratio aero-engines the strong interaction between the jet and aircraft wing leads to intensified installed jet noise. An experiment is carried out in this paper to study the effects of lobed nozzles on installed jet noise. It is found that the lobed nozzles, compared to round nozzles, have similar effects on installed jet noise for all the plate positions and Mach numbers tested. On the shielded side of the plate, the use of lobed nozzles leads to a noise reduction in the intermediate-and high-frequency regimes, which is thought to be due to a combination of enhanced jet mixing and more effective shielding effects by the flat plate. On the reflected side of the plate, noise reduction is only achieved in the intermediate frequency range; the little noise reduction or a slight noise increase observed in the high-frequency regime is likely due to enhanced jet mixing. On both sides of the plates, little noise reduction is achieved for the low-frequency noise due to the scattering of jet instability waves. This is likely to be caused by the fact that lobed nozzles cause negligible change to the dominant mode 0 (axisymmetric) jet instability waves. That the jet mean flow quickly becomes axisymmetric downstream of the jet exit could also play a role.

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Section: Resultsmentioning

confidence: 99%

“…Recent studies have shown that the low-frequency noise intensification observed in installed jets is due to the scattering of jet instability waves (Lyu and Dowling 2016, 2018aCavalieri et al 2014). The understanding of this mechanism is important in developing new noise reduction methods.…”

Section: Introductionmentioning

confidence: 99%

An experimental study of the effects of lobed nozzles on installed jet noise

Lyu

Dowling

2019

Exp Fluids

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“…Using (2.24), both the spectra and the directivity patterns of the far-field sound can be readily plotted. Since the model needs an input of the near-field pressure spectra, in this paper we use the spectra measured in the experiment carried out by the authors in an earlier study , 2018. This experiment was carried out in the anechoic chamber at the Engineering Department at the University of Cambridge, where a round, cold, Mach 0.5 jet of diameter 2.54 cm was operated both with and without a nearby flat plate.…”

Section: Resultsmentioning

confidence: 99%

“…This experiment was carried out in the anechoic chamber at the Engineering Department at the University of Cambridge, where a round, cold, Mach 0.5 jet of diameter 2.54 cm was operated both with and without a nearby flat plate. For a detailed description of the experimental setup used to measure the near-field pressure spectra, the readers are referred to the earlier works , 2018).…”

Section: Resultsmentioning

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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“…In this section, the near-field hydrodynamic pressure -edge scattering model developed by Lyu and Dowling [1] for the modelling of the jet-installation noise is presented. The source parameters herein will be obtained from the LES simulation.…”

Section: Acoustic Noise Modelsmentioning

confidence: 99%

Jet Installation Noise Modelling Informed by GPU LES

Abid

Markesteijn

Gryazev

et al. 2022

28th AIAA/CEAS Aeroacoustics 2022 Conference

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Jet installation beneath a wing significantly enhances jet noise at low frequencies, and its physical mechanism must be comprehended to develop efficient noise reduction solutions. A numerical investigation on the jet-installation noise is performed using Wall Modelled Large Eddy Simulation (WMLES) performed using the high-resolution CABARET method accelerated on Graphics Processing Units. To simulate jet installation, a flat plate is put outside of the jet's plume, causing a rise in noise levels due to the scattering of near-field hydrodynamic waves at the trailing edge of the plate. The configuration adopted in this work replicates a series of experiments performed at the University of Bristol, against which the numerical results are validated. The numerical simulation is performed for Mach numbers of 0.5 and 0.9, and the influence of the selected noise reduction technique, i.e., the usage of chevron nozzles in comparison with the baseline round nozzle, on the jet-installation is studied by modelling SMC006 chevron nozzle. The properties of jet-hydrodynamic pressure variations and their effect on nozzle type and Mach number are investigated. Far-field noise spectra from the isolated and installed jet cases, obtained through the Ffowcs-Williams Hawkings method, are compared at different polar angles. In addition, a hybrid semi-analytical hydrodynamic-edge scattering prediction model is implemented following the model of Lyu and Dowling [1] to analyse jet-installation noise, using inputs obtained directly from the LES calculation. The implemented model is found to capture the correct physics at peak jet installation frequencies and can be used as a robust prediction tool for jet-installation noise optimisation in the future.

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Experimental validation of the hybrid scattering model of installed jet noise

Cited by 12 publications

References 33 publications

An experimental study of the effects of lobed nozzles on installed jet noise

An experimental study of the effects of lobed nozzles on installed jet noise

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

Jet Installation Noise Modelling Informed by GPU LES

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