Adaptation of the Azimuthal Decomposition Technique to Jet Noise Measurements in Full-Scale Tests

Faranosov, G. A.; Belyaev, I. V.; Kopiev, V. F.; Zaytsev, M. Yu.; Aleksentsev, A. A.; Bersenev, Yuly V.; Chursin, Valery; Viskova, T.A.

doi:10.2514/1.j055001

Cited by 21 publications

(6 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The superdirectivity of the extended wavepacket source is made clear by plotting the sound pressure level as a function of Θ, as in figure 8, where it is compared with measurements of the axisymmetric part of the sound radiation of a turbulent jet of Mach number, M = 0.6, issuing from a round nozzle whose internal boundary layer was tripped and fully turbulent [5]. Sound radiation to low polar angles of this jet is indeed superdirective, indicating that it is driven by an extended source structure characterised by large values of k h L. Such strong directivity of the axisymmetric radiation of subsonic jets has been verified in tests of actual jet engines by Faranosov et al [6]…”

Section: Compact and Non-compact Sources (Example2m)mentioning

confidence: 69%

“…Whereas the energetically dominant turbulence structures are relatively small, scaling with the local momentum thickness of the shear layer [1], the acoustic field comprises larger scales, that are, furthermore, more organised. An azimuthal Fourier-series decomposition of the acoustic field in laboratory experiments reveals that lowangle radiation (measured with respect to the downstream jet axis) is predominantly axisymmetric [2,3,4,5], and recent measurements show that this is also the case for full-scale jet engines [6]. Large-eddy simulation data shows that while radiation at higher frequencies does involve higher-order azimuthal modes [7], it nonetheless remains significantly more organised than the turbulence from which it issues.…”

Section: Introductionmentioning

confidence: 93%

“…The number of spatial oscillations that arise between the beginning of perturbation growth and the end of its decay depends on the value of k h L. When this parameter is small the source is compact, as per figure 5(a); when it is large, on the other hand, the source is an extended wavepacket, as per Figure 5(b). 6 . Early sound-source models, such as proposed by Lighthill for instance, were based on an assumption of com- Fig.…”

Section: The Line-source Modelmentioning

confidence: 99%

See 2 more Smart Citations

Wave-Packet Models for Jet Dynamics and Sound Radiation

Cavalieri

Jordan

Lesshafft

2019

Applied Mechanics Reviews

113

View full text Add to dashboard Cite

Organized structures in turbulent jets can be modeled as wavepackets. These are characterized by spatial amplification and decay, both of which are related to stability mechanisms, and they are coherent over several jet diameters, thereby constituting a noncompact acoustic source that produces a distinctive directivity in the acoustic field. In this review, we use simplified model problems to discuss the salient features of turbulent-jet wavepackets and their modeling frameworks. Two classes of model are considered. The first, that we refer to as kinematic, is based on Lighthill's acoustic analogy, and allows an evaluation of the radiation properties of sound-source functions postulated following observation of jets. The second, referred to as dynamic, is based on the linearized, inhomogeneous Ginzburg–Landau equation, which we use as a surrogate for the linearized, inhomogeneous Navier–Stokes system. Both models are elaborated in the framework of resolvent analysis, which allows the dynamics to be viewed in terms of an input–ouput system, the input being either sound-source or nonlinear forcing term, and the output, correspondingly, either farfield acoustic pressure fluctuations or nearfield flow fluctuations. Emphasis is placed on the extension of resolvent analysis to stochastic systems, which allows for the treatment of wavepacket jitter, a feature known to be relevant for subsonic jet noise. Despite the simplicity of the models, they are found to qualitatively reproduce many of the features of turbulent jets observed in experiment and simulation. Sample scripts are provided and allow calculation of most of the presented results.

show abstract

Section: Compact and Non-compact Sources (Example2m)mentioning

confidence: 69%

Section: Introductionmentioning

confidence: 93%

Section: The Line-source Modelmentioning

confidence: 99%

See 1 more Smart Citation

Wave-Packet Models for Jet Dynamics and Sound Radiation

Cavalieri

Jordan

Lesshafft

2019

Applied Mechanics Reviews

113

View full text Add to dashboard Cite

show abstract

“…[14]. Recently, Faranosov et al [19] compared the similarity spectra to an azimuthal decomposition of an aircraft engine on a static test bench. All of these studies have focused solely on the turbulent mixing noise.…”

Section: Introductionmentioning

confidence: 99%

Inclusion of Broadband Shock-Associated Noise in Spectral Decomposition of Noise from High-performance Military Aircraft

Neilsen

Vaughn

Gee

et al. 2018

2018 AIAA/CEAS Aeroacoustics Conference

View full text Add to dashboard Cite

Attempts to reduce the noise from high-performance military aircraft requires an understanding of the different jet noise generation mechanisms. The primary noise sources originate from interactions between turbulent mixing noise associated with large and finescale turbulent structures and the ambient air. A nonideally expanded jet also contains broadband shock-associated noise. A three-way decomposition of the spectral density measured near a tied-down F-35B quantifies the contribution from each type of noise. The decomposition is performed on noise from a ground-based, linear array of microphones, approximately 8 m from the estimated shear layer, which spanned an angular aperture of 35° to 152° (relative to engine inlet). This large spatial aperture allows for a detailed investigation into the spatial variation in broadband shock-associated noise and fine and large-scale turbulent mixing noise. The spectral decompositions match the measured spectral levels with three main exceptions: 1) the F-35B noise contains multiple spectral peaks in the maximum radiation region, 2) nonlinear propagation increases the high-frequency spectral levels, and 3) the low-frequency levels in the maximum radiation region are less than those predicted by the large-scale similarity spectrum. The main peak of the F-35B broadband shock-associated noise, evident from 35°-70°, has the same characteristic shape and variation in peak frequency as overexpanded, laboratory-scale jets. The F-35B broadband shockassociated noise peak level and width exhibit different trends than laboratory-scale BBSAN and those recently reported for the F/A-18E [

show abstract

“…2016; Faranosov et al. 2017). The trend observed here is consistent with the literature (see figure 9 of Brès et al.…”

Section: Empirical Modelling Of the Acoustically Efficient Forcing Co...mentioning

confidence: 99%

An empirical model of noise sources in subsonic jets

Karban

Bugeat²,

Towne

et al. 2023

J. Fluid Mech.

View full text Add to dashboard Cite

Modelling the noise emitted by turbulent jets is made difficult by their acoustic inefficiency: only a tiny fraction of the near-field turbulent kinetic energy is propagated to the far field as acoustic waves. As a result, jet-noise models must accurately capture this small, acoustically efficient component hidden among comparatively inefficient fluctuations. In this paper, we identify this acoustically efficient near-field source from large-eddy simulation data and use it to inform a predictive model. Our approach uses the resolvent framework, in which the source takes the form of nonlinear fluctuation terms that act as a forcing on the linearised Navier–Stokes equations. First, we identify the forcing that, when acted on by the resolvent operator, produces the leading spectral proper orthogonal decomposition modes in the acoustic field for a Mach 0.4 jet. Second, the radiating components of this forcing are isolated by retaining only portions with a supersonic phase speed. This component makes up less than 0.05 % of the total forcing energy but generates most of the acoustic response, especially at peak (downstream) radiation angles. Finally, we propose an empirical model for the identified acoustically efficient forcing components. The model is tested at other Mach numbers and flight-stream conditions and predicts noise within 2 dB accuracy for a range of frequencies, downstream angles and flight conditions.

show abstract

Adaptation of the Azimuthal Decomposition Technique to Jet Noise Measurements in Full-Scale Tests

Cited by 21 publications

References 43 publications

Wave-Packet Models for Jet Dynamics and Sound Radiation

Wave-Packet Models for Jet Dynamics and Sound Radiation

Inclusion of Broadband Shock-Associated Noise in Spectral Decomposition of Noise from High-performance Military Aircraft

An empirical model of noise sources in subsonic jets

Contact Info

Product

Resources

About