Computational AeroAcoustics of a Realistic Co-Axial   Engine, possibly Equipped with Acoustic Liners

Redonnet, Stephane; Mincu, Ciprian; Delattre, Grégory

doi:10.2514/6.2010-3717

Cited by 8 publications

(5 citation statements)

References 13 publications

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“…As an illustration, Figure 16 showcases a direct application of the present CAA/TDIBC approach to the mitigation of the aft fan noise emitted by a turbojet engine in take-off conditions. 29,30 Despite the harsh thermodynamic conditions occurring there (highly subsonic hot jet mean flow, cf. Figure 16(a)), these simulations successfully showcased how lining the exhaust with noise absorbing material panels (cf.…”

Section: Computational Results and Analysis For Configuration #1 (Wiremesh Material C3p0s2)mentioning

confidence: 99%

“…perforate materials) were traditionally employed within engine nacelles so as to damp the fan noise components radiating through the inlet. 27 Their use is now generalized to other parts of the engines, e.g., within the exhaust [28][29][30][31] so as to damp that fan noise aft component propagating downstream, as well as within the nacelle's fan tip clearance area 27,32 so as to attenuate part of the fan noise generation mechanisms. Besides, the use of new class of acoustic liners (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Notably, this TDIBC was implemented 67 within ONERA's CAA solver (sAbrinA code [77][78][79][80] ), the resulting CAA/TDIBC approach being successfully applied to various problems of increasing complexity. 29,30 Here too, however, the TDIBC had been primarily validated upon NASA experimental databases based on ceramic materials, 67 e.g., the so-called ceramic tubular CT73 for which it had been originally designed. 47 Therefore, it appeared necessary to further assess how this TDIBC might also replicate accurately some acoustic liners whose nature and behaviour would intrinsically differ from that of ceramic tubular materials.…”

Section: Introductionmentioning

confidence: 99%

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Further assessment of a time domain impedance boundary condition for the numerical simulation of noise-absorbing materials

Redonnet

2021

International Journal of Aeroacoustics

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In regard to the mitigation of environmental noise across major industry sectors, the present study focuses on the numerical prediction of passive noise reduction devices. Here, it is further explored how the noise attenuation induced by locally reacting noise absorbing materials (also called acoustic liners) can be simulated using a time domain highly accurate Computational AeroAcoustics (CAA) method. To this end, it is assessed how a classical Time Domain Impedance Boundary Condition (TDIBC) can effectively model acoustic liners of practical interest, including when the latter are exposed to realistic conditions (grazing flow and noise excitation). The investigation consists in numerically reproducing two experimental campaigns initially performed at NASA Langley Research Center. Two different materials are considered (honeycomb superimposed with perforate or wiremesh resistive face-sheet), each being characterized by a specific noise attenuation behaviour ( e.g. dependency on the flow conditions and/or noise excitation). Each material is tested under various flow conditions ( e.g. grazing flow of Mach up to 0.5) and/or noise source excitation ( e.g. multiple tones of level up to 140 dB each). The results demonstrate the ability of the underlying CAA/TDIBC approach to simulate realistic acoustic liners in non-trivial configurations, with enough physical accuracy ( e.g. correct capture of the noise attenuation characteristics) and numerical robustness ( e.g. absence of instabilities). The study also reveals that, independent from the CAA/TDIBC approach itself, some specific pre-processing tasks (e.g. impedance eduction and subsequent TDIBC calibration) may play a bigger role than expected, in practice.

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Section: Computational Results and Analysis For Configuration #1 (Wiremesh Material C3p0s2)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Further assessment of a time domain impedance boundary condition for the numerical simulation of noise-absorbing materials

Redonnet

2021

International Journal of Aeroacoustics

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“…Such an analytical‐CAA coupled calculation exercise had been achieved and validated in a previous effort ; for such a calculation, and although this could have been done (such as was carried out in another framework ), the sphere obstacle was not CAA‐meshed, so that the propagation grid could be taken as an ideal one, that is, of a homogenous Cartesian type. The reason for doing so was to minimize at best all possible side effects (such as metric errors) that could have biased the analysis.…”

Section: Further Illustration and Validation Of The Equivalent Intrinmentioning

confidence: 99%

A novel optimization technique for explicit finite‐difference schemes with application to AeroAcoustics

Cunha

Redonnet

2015

Numerical Methods in Fluids

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SummaryThe present paper addresses the optimization of finite‐difference schemes when these are to be used for numerically approximating spatial derivatives in aeroacoustics evolution problems. With that view in mind, finite‐difference operators are firstly detailed from a theoretical point of view. Secondly, time, the way such operators can be optimized in a spectral‐like sense is recalled, before the main limitations of such an optimization are highlighted. This leads us to propose an alternative optimization approach of innovative character. Such a novel optimization technique consists of enhancing the scheme's formal accuracy through a minimization of its leading‐order truncation error. This so‐called intrinsic optimization procedure is first detailed, before it is thoroughly analyzed, from both a theoretical and a practical point of view. The second part of the paper focuses on two particular intrinsically optimized schemes, which are carefully assessed via a direct comparison against their standard and/or spectral‐like optimized counterparts, such a comparative exercise being conducted utilizing several academic test cases of increasing complexity. There, it is shown how intrinsically optimized schemes indeed constitute an advantageous alternative to either the standard or the spectral‐like optimized ones, being allotted with both (i) the better scalability of the former scheme with respect to grid convergence effects when the grid density increases and (ii) the higher accuracy of the latter scheme when the discretization level becomes marginal. Thanks to that, such intrinsically optimized schemes offer very good trade‐offs in terms of (i) accuracy; (ii) robustness; and (iii) numerical efficiency (CPU cost). Copyright © 2015 John Wiley & Sons, Ltd.

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“…As a possible counter-measure against sound emissions generated by a modern aero engine, the application of acoustic liners within the second exhaust is discussed, see e.g. [6]. A large number of small holes perpendicular to the surface followed by a honeycomb pattern produce a complex interaction of the grazing exhaust flow of velocities up to 240 [m/s] and the acoustic field, where non-linear effects of vortex generation and dissipation as well as backscattering are non-negligible and play an important role for the dissipative behavior of the liner.…”

Section: Introductionmentioning

confidence: 99%

Frequency domain simulations for the determination of liner effects on longitudinal wave propagation

Schulze

Sattelmayer

2015

International Journal of Aeroacoustics

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Frequency domain simulations are carried out in order to determine the effects of a liner on the propagation of longitudinal waves. On the basis of a CFD/CAA approach, three-dimensional linearized Euler equations (LEE) are transformed into frequency space and discretized using a stabilized Finite-Element technique to provide stable solution procedures and meaningful results. The code is validated on a Grazing Incidence Tube (GIT), which is operated at the NASA Langley Research Center. Results show that the frequency transformed LEE are very suitable to predict the acoustic propagation using experimentally determined liner impedances for different Mach numbers in the tube and further acoustic boundary conditions both at inlet and outlet of the test rig. In comparison to time-domain based approaches, computational times are reduced substantially and numerical instability issues are prevented. Furthermore, the relevance of detailed mean flow profiles and Myers impedance boundary conditions for the accurate prediction of the liner effect on the acoustic wave propagation is addressed. 1026 Frequency domain simulations for the determination of liner effects on longitudinal wave propagation aeroacoustics volume 14 • number 7 • 2015 1027 1028 Frequency domain simulations for the determination of liner effects on longitudinal wave propagation

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Computational AeroAcoustics of a Realistic Co-Axial Engine, possibly Equipped with Acoustic Liners

Cited by 8 publications

References 13 publications

Further assessment of a time domain impedance boundary condition for the numerical simulation of noise-absorbing materials

Further assessment of a time domain impedance boundary condition for the numerical simulation of noise-absorbing materials

A novel optimization technique for explicit finite‐difference schemes with application to AeroAcoustics

Frequency domain simulations for the determination of liner effects on longitudinal wave propagation

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