Resolvent analysis applied to acoustic analogies

Abreu, Leandra I.; Nogueira, Petrônio A. S.; Nilton, Maurício M.; Cavalieri, André V. G.

doi:10.2514/6.2019-2402

Cited by 2 publications

(2 citation statements)

References 19 publications

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“…Note that the above analysis could be applied when using an acoustic analogy as well. A Green's function that is used to solve the acoustic propagation problem in an acoustic analogy establishes a linear relation between the source and the acoustic field, and hence, can be described by a matrix left-multiplying the source for the discretised system, which reduces it to an input-output form as shown above (Abreu et al 2019). We will use this approach to obtain a low-rank representation of the forcing that is responsible for most of the acoustic energy radiated by a turbulent jet.…”

Section: Resolvent-based Extended Spectral Proper Orthogonal Decompos...mentioning

confidence: 99%

An empirical model of noise sources in subsonic jets

Karban

Bugeat²,

Towne

et al. 2023

J. Fluid Mech.

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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.

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Section: Resolvent-based Extended Spectral Proper Orthogonal Decompos...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

show abstract

“…This approach decomposes the problem into forcing and response modes and seeks to determine dominant source modes for the development of reduced-order models of the sound field. An example of its application to the trailing-edge problem is given in Abreu et al (2019).…”

Section: Introductionmentioning

confidence: 99%

Rapid distortion theory on transversely sheared mean flows of arbitrary cross-section

2019

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This paper is concerned with rapid distortion theory on transversely sheared mean flows that (among other things) can be used to analyse the unsteady motion resulting from the interaction of a turbulent shear flow with a solid surface. It expands on a previous analysis of Goldstein et al. (J. Fluid Mech., vol. 824, 2017, pp. 477–512) that uses a pair of conservation laws to derive upstream boundary conditions for planar mean flows and extends these findings to transversely sheared flows of arbitrary cross-section. The results, which turn out to be quite general, are applied to the specific case of a round jet interacting with the trailing edge of a flat plate and are used to calculate the radiated sound field, which is then compared with experimental data taken at the NASA Glenn Research Center.

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Resolvent analysis applied to acoustic analogies

Cited by 2 publications

References 19 publications

An empirical model of noise sources in subsonic jets

An empirical model of noise sources in subsonic jets

Rapid distortion theory on transversely sheared mean flows of arbitrary cross-section

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