Relation between the Generalized Acoustic Analogy and Lilley's Contributions to Aeroacoustics

Goldstein, M. E.

doi:10.1260/1475-472x.9.4-5.401

Cited by 13 publications

(12 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The governing acoustic perturbations may be obtained by writing the Navier-Stokes (NS) equations as a set of mean flow equations (referred to as a non-radiating base flow), plus a set of linear equations for the fluctuating components of the motion. By selecting a set of five appropriately defined perturbation variables, four of them nonlinear, Goldstein [14] shows that the left-hand side of the acoustic equations resemble those obtained by linearizing the convective form of Euler equations about a similar base flow. Further, by assuming the mean flow as locally parallel, the factors on the left-hand side of momentum and energy equations that explicitly depend on the viscous stresses reduce to higher order terms and are neglected.…”

Section: Formulation Of the Scrubbing Noise Problemmentioning

confidence: 99%

“…The pressure variable ′ π consists of additional (higher order) terms that reduce to zero in the far field acoustic domain, and the source term on the right hand side of (1) is defined according to the generalized acoustic analogy [14].…”

Section: Formulation Of the Scrubbing Noise Problemmentioning

confidence: 99%

“…The problem at hand is thus reduced to solving equation (9) subject to the two boundary conditions (14) and (21).…”

Section: Formulation Of the Scrubbing Noise Problemmentioning

confidence: 99%

“…Note that far-field radiation condition (14) combined with (33) also leads to the requirement that S 2 > 0.…”

Section: Stationary Phase Solutionmentioning

confidence: 99%

See 3 more Smart Citations

Acoustics of Jet Surface Interaction - Scrubbing Noise

Khavaran¹

2014

20th AIAA/CEAS Aeroacoustics Conference

View full text Add to dashboard Cite

Concepts envisioned for the future of civil air transport consist of unconventional propulsion systems in the close proximity to the structure or embedded in the airframe. While such integrated systems are intended to shield noise from the community, they also introduce new sources of sound. Sound generation due to interaction of a jet flow past a nearby solid surface is investigated here using the generalized acoustic analogy theory. The analysis applies to the boundary layer noise generated at and near a wall, and excludes the scattered noise component that is produced at the leading or the trailing edge. While compressibility effects are relatively unimportant at very low Mach numbers, frictional heat generation and thermal gradient normal to the surface could play important roles in generation and propagation of sound in high speed jets of practical interest. A general expression is given for the spectral density of the far field sound as governed by the variable density Pridmore-Brown equation. The propagation Green's function is solved numerically for a high aspect-ratio rectangular jet starting with the boundary conditions on the surface and subject to specified mean velocity and temperature profiles between the surface and the observer. It is shown the magnitude of the Green's function decreases with increasing source frequency and/or jet temperature. The phase remains constant for a rigid surface, but varies with source location when subject to an impedance type boundary condition. The Green's function in the absence of the surface, and flight effects are also investigated.

show abstract

Section: Formulation Of the Scrubbing Noise Problemmentioning

confidence: 99%

Section: Formulation Of the Scrubbing Noise Problemmentioning

confidence: 99%

See 2 more Smart Citations

Acoustics of Jet Surface Interaction - Scrubbing Noise

Khavaran¹

2014

20th AIAA/CEAS Aeroacoustics Conference

View full text Add to dashboard Cite

show abstract

“…However, for sound predictions based on the LES that had to resolve a mixture of sound generation and propagation effects that appear in the definition of the Lighthill stress, large errors in overall sound pressure levels were reported. This revealed the importance of explicitly representing linear meanflow propagation effects in the acoustic analogy equations, which are partly accounted for in the Lilley acoustic analogy and, most consistently, in the Goldstein generalised acoustic analogy (for a detailed discussion of the differences between the two analogies see (Goldstein 2010)).…”

Section: Introductionmentioning

confidence: 99%

A volume integral implementation of the Goldstein generalised acoustic analogy for unsteady flow simulations

Semiletov

Karabasov

2018

J. Fluid Mech.

View full text Add to dashboard Cite

A new volume integral method based on the Goldstein generalised acoustic analogy is developed and directly applied with large-eddy simulation (LES). In comparison with the existing Goldstein generalised acoustic analogy implementations, the current method does not require the computation and recording of the expensive fluctuating stress autocovariance function in the seven-dimensional space–time. Until now, the multidimensional complexity of the generalised acoustic analogy source term has been the main barrier to using it in routine engineering calculations. The new method only requires local pointwise stresses as an input that can be routinely computed during the flow simulation. On the other hand, the new method is mathematically equivalent to the original Goldstein acoustic analogy formulation, and, thus, allows for a direct correspondence between different effective noise sources in the jet and the far-field noise spectra. The implementation is performed for conditions of a high-speed subsonic isothermal jet corresponding to the Rolls-Royce SILOET experiment and uses the LES solution based on the CABARET solver. The flow and noise solutions are validated by comparison with experiment. The accuracy and robustness of the integral volume implementation of the generalised acoustic analogy are compared with those based on the standard Ffowcs Williams–Hawkings surface integral method and the conventional Lighthill acoustic analogy. As a demonstration of its capabilities to investigate jet noise mechanisms, the new integral volume method is applied to analyse the relative importance of various noise generation and propagation components within the Goldstein generalised acoustic analogy model.

show abstract

Combustion instability effect on sound generation by jet diffusion flame

Xiong

Jiang

2018

Journal of Applied Physics

View full text Add to dashboard Cite

This paper presented a numerical study of flow instability effects on the sound generation by jet diffusion flames. Numerical simulation coupled with the acoustic analogy based on Lilley’s equation was employed to predict the sound radiation. A parametric study by varying the Froude number was carried out, and simulations were performed with different levels of external forcing to shed light on the competing acoustic responses of the buoyant and jet preferred instabilities. The detailed sound source structure was provided by the flow details. It is shown that the increase of buoyancy is responsible for the development of the acoustic source in the downstream flame region. When the Froude number is larger than unity, only low-frequency noise will be affected, and when the Froude number is less than unity, combustion-induced buoyancy has a further positive impact on the noise level in the high-frequency region. The jet preferred instability caused by external disturbance can improve the intensity of the sound source and may further be amplified as the noise peak, depending on the buoyancy level. An acoustic transfer function was therefore analyzed to characterize the different acoustic responses. The results showed that there is a positive correlation between the buoyancy level and the acoustical response rate of external disturbance, and the high-frequency disturbance is much easier to be amplified by flame than that with low frequency, especially in the downstream flow field.

show abstract

Relation between the Generalized Acoustic Analogy and Lilley's Contributions to Aeroacoustics

Cited by 13 publications

References 26 publications

Acoustics of Jet Surface Interaction - Scrubbing Noise

Acoustics of Jet Surface Interaction - Scrubbing Noise

A volume integral implementation of the Goldstein generalised acoustic analogy for unsteady flow simulations

Combustion instability effect on sound generation by jet diffusion flame

Contact Info

Product

Resources

About