A numerical and experimental investigation of the dissipation mechanisms of resonant acoustic liners

Tam, Christopher K. W.; Kurbatskii, Konstantin A.; Ahuja, K. K.; Gaeta, Richard

doi:10.2514/6.2001-2262

Cited by 30 publications

(38 citation statements)

References 13 publications

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“…As such, this represents a significant advance for the understanding of oscillatory, orifice flows of interest in the predictive modeling of nonlinear acoustic resistance.Experimental support for the vortex shedding dissipation mechanism is provided in the work of Tam, Kurbatskii, Ahuja and Gaeta. 15 In their experiment, laser visualization was used to scan the unsteady flow field inside the resonator. Evidence of the observation of shed vortices was reported in their work.…”

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confidence: 99%

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A computational and experimental study of resonators in three dimensions

Tam

Huang

Jones

et al. 2010

Journal of Sound and Vibration

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In a previous work by the present authors, a computational and experimental investigation of the acoustic properties of two-dimensional slit resonators was carried out. The present paper reports the results of a study extending the previous work to three dimensions. This investigation has two basic objectives. The first is to validate the computed results from direct numerical simulations of the flow and acoustic fields of slit resonators in three dimensions by comparing with experimental measurements in a normal incidence impedance tube. The second objective is to study the flow physics of resonant liners responsible for sound wave dissipation. Extensive comparisons are provided between computed and measured acoustic liner properties with both discrete frequency and broadband sound sources. Good agreements are found over a wide range of frequencies and sound pressure levels. Direct numerical simulation confirms the previous finding in two dimensions that vortex shedding is the dominant dissipation mechanism at high sound pressure intensity. However, it is observed that the behavior of the shed vortices in three dimensions is quite different from those of two dimensions. In three dimensions, the shed vortices tend to evolve into ring (circular in plan form) vortices, even though the slit resonator opening from which the vortices are shed has an aspect ratio of 2.5. Under the excitation of discrete frequency sound, the shed vortices align themselves into two regularly spaced vortex trains moving away from the resonator opening in opposite directions. This is different from the chaotic shedding of vortices found in two-dimensional simulations. The effect of slit aspect ratio at a fixed porosity is briefly studied. For the range of liners considered in this investigation, it is found that the absorption coefficient of a liner increases when the open area of the single slit is subdivided into multiple, smaller slits.impedance would be free of empirical constants. In addition to the possibility of becoming an impedance prediction tool, CAA offers an enhancement to semi-empirical model prediction by better quantifying constants that heretofore have necessitated elaborate experimentation, thereby providing a means to investigate and better understand the mechanisms by which an acoustic liner dissipates incident sound waves. The openings of an acoustic liner are quite small. This makes it difficult to perform experimental observations and measurements of the fluid flow and acoustic fields in and around an acoustic liner. On the other hand, small liner openings are no hindrance to CAA simulations. Moreover, numerical simulations using CAA methodologies can provide a complete set of space-time data. This is an invaluable asset for flow physics investigation and analysis. At the present time, the goals of using CAA methodology for first-principles impedance prediction and for investigation of acoustic wave dissipation mechanisms have not been fully attained. Nevertheless, significant advances have been made. Further efforts...

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confidence: 99%

“…Experimental support for the vortex shedding dissipation mechanism is provided in the work of Tam, Kurbatskii, Ahuja and Gaeta. 15 In their experiment, laser visualization was used to scan the unsteady flow field inside the resonator. Evidence of the observation of shed vortices was reported in their work.…”

mentioning

confidence: 99%

A computational and experimental study of resonators in three dimensions

Tam

Huang

Jones

et al. 2010

Journal of Sound and Vibration

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“…To capture subsonic sound generation, the sketched incompressible method it is extended to compressible flow following the simulation approach as being used by Tam & Kurbatski [28][29][30] for Direct Numerical Simulation (DNS) simulation of subsonic cold-flow sound problems. Refer also to the discussion of this approach in Ref.…”

Section: Simulation Methodsmentioning

confidence: 99%

Simulation of Cold Jet Installation Noise using a Stochastic Backscatter Model

Ewert

Neifeld

Boenke

2017

23rd AIAA/CEAS Aeroacoustics Conference

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This work presents first results obtained with partly scale resolving simulation for two different installation noise problems involving a cold jet interacting with a wing. Similar to very large-eddy simulation (VLES), the resolvable very large scales of turbulent fluctuations are directly calculated and the dissipation of the non-resolved scales is accounted for by a subfilter scale stress model. In addition, stochastic forcing in space and time is applied to model turbulent backscatter. The paper presents and discusses the rationale to explicitly realize turbulent backscatter along with details of the proposed stochastic backscatter model and its calibration. As a novel approach, the entire subfilter forcing function is modeled by means of an eddy-relaxation source term that provides a combined model for forcing and dissipation. The relaxation parameter defines the amount of correlation of the subfilter forcing with resolved quantities. Its proper calibration is achieved using decaying homogeneous isotropic turbulence. Furthermore, characteristics of the backscatter forcing are analyzed from synthetic turbulence data. The first jet-wing interaction problem studied is based on a generic static jet interacting with a non-inclined rectangular wing. The second problem deals with a dual-stream nozzle installed at a high-lift wing with deployed flap and slat in wind tunnel flow under approach conditions. For both problems installation noise from the airframe yields higher peak levels than the jet-noise contribution alone. For the first problem, relative to the corresponding jet spectrum a low-frequency narrow-band contribution is observed that can be attributed to coherent jet structures interacting with the airfoil trailing edge. Very good agreement with measured spectra is obtained. For the second problem a broadband airframe installation contribution to the overall spectrum is predicted with peak frequency above the jet contribution.

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“…These simulations neglect both the effect of the grazing flow on the impedance and the effect of the impedance on the flow. Other simulations are based on the full nonlinear Navier-Stokes equations and the flow is computed together with the acoustic field [17,18,19,20,21,22]. Among these simulations, some include the liner back cavity and the face sheet perforations [17,18,19,20] so as to include all possible flow-acoustics interactions.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of a turbulent channel flow with an acoustic liner

Sebastian

Marx

Fortuné

2019

Journal of Sound and Vibration

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Numerical simulations of a compressible turbulent channel flow with an acoustic impedance boundary condition are performed to assess how the flow is modified compared with a channel flow with rigid walls. When the liner resonance frequency is not too large and the resistance sufficiently small, turbulent statistics deviate from those obtained with rigid walls and surface waves are found traveling along the liner surface. For small resonance frequencies these waves are two-dimensional, they have a large wavelength compared to the turbulent structures and modulate these structures. As a result, they transport momentum toward the impedance wall, causing a drag increase. When the resonance frequency increases, the waves along the liner surface progressively lose their spanwise coherence while their streamwise wavelength decreases to get close to the flow typical length scales, which may also result in a drag increase when the resistance is sufficiently small. In the cases in which the surface waves are twodimensional, a connection is established between them and the unstable modes computed by using a linear stability analysis. Given the streamwise periodicity of the channel, a temporal stability analysis is performed rather than a spatial analysis, the latter being more frequently encountered in acoustic mode computations. This temporal analysis shows that the unstable mode in the vicinity of an acoustic liner arises from the A-branch of wall modes.

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A numerical and experimental investigation of the dissipation mechanisms of resonant acoustic liners

Cited by 30 publications

References 13 publications

A computational and experimental study of resonators in three dimensions

A computational and experimental study of resonators in three dimensions

Simulation of Cold Jet Installation Noise using a Stochastic Backscatter Model

Numerical simulation of a turbulent channel flow with an acoustic liner

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