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Nonlinear mechanisms of sound generation in a perturbed parallel jet flow

Nonlinear mechanisms of sound generation in a perturbed parallel jet flow
Nonlinear mechanisms of sound generation in a perturbed parallel jet flow
An initial value problem with relevance to jet noise is investigated. A plane parallel jet flow is subjected to a spatially localized initial disturbance and is then left to evolve according to the two-dimensional compressible Navier–Stokes equations. The hydrodynamic response is in the form of a convecting vortex packet. The Ffowcs Williams–Hawkings approach is formulated in the time domain and used to extrapolate from the simulated near field to the acoustic far field. The predominant downstream sound radiation comes from an early stage of nonlinear development of the vortex packet. Two simplified models to account for the radiation are introduced, based on nonlinear mode interactions on a prescribed base flow. The first uses two sets of linearized Euler equations, coupled via the inviscid Lilley–Goldstein acoustic analogy. This formulation separates the linear sound field from the sound field driven by nonlinear interactions; qualitative agreement of the latter with the Navier–Stokes computations demonstrates the importance of nonlinear interactions. The second model uses combinations of linear inviscid eigenmodes to drive the sound field, which allows extraction of the dominant mode interactions responsible for the observed radiation pattern. The results indicate that a difference-wavenumber nonlinear interaction mechanism dominates sound radiation from subsonic instability modes in shear flows.
0022-1120
1-23
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Morfey, C.L.
d5f9a8d0-7d8a-4915-a522-bf49dee111f2
Hu, Z.W.
dd985844-1e6b-44ba-9e1d-fa57c6c88d65
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Morfey, C.L.
d5f9a8d0-7d8a-4915-a522-bf49dee111f2
Hu, Z.W.
dd985844-1e6b-44ba-9e1d-fa57c6c88d65

Sandham, N.D., Morfey, C.L. and Hu, Z.W. (2006) Nonlinear mechanisms of sound generation in a perturbed parallel jet flow. Journal of Fluid Mechanics, 565, 1-23. (doi:10.1017/S0022112006001315).

Record type: Article

Abstract

An initial value problem with relevance to jet noise is investigated. A plane parallel jet flow is subjected to a spatially localized initial disturbance and is then left to evolve according to the two-dimensional compressible Navier–Stokes equations. The hydrodynamic response is in the form of a convecting vortex packet. The Ffowcs Williams–Hawkings approach is formulated in the time domain and used to extrapolate from the simulated near field to the acoustic far field. The predominant downstream sound radiation comes from an early stage of nonlinear development of the vortex packet. Two simplified models to account for the radiation are introduced, based on nonlinear mode interactions on a prescribed base flow. The first uses two sets of linearized Euler equations, coupled via the inviscid Lilley–Goldstein acoustic analogy. This formulation separates the linear sound field from the sound field driven by nonlinear interactions; qualitative agreement of the latter with the Navier–Stokes computations demonstrates the importance of nonlinear interactions. The second model uses combinations of linear inviscid eigenmodes to drive the sound field, which allows extraction of the dominant mode interactions responsible for the observed radiation pattern. The results indicate that a difference-wavenumber nonlinear interaction mechanism dominates sound radiation from subsonic instability modes in shear flows.

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Published date: 2006

Identifiers

Local EPrints ID: 43442
URI: https://eprints.soton.ac.uk/id/eprint/43442
ISSN: 0022-1120
PURE UUID: beea4835-39cf-411c-8a3e-ea304e0059c3
ORCID for N.D. Sandham: ORCID iD orcid.org/0000-0002-5107-0944

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Date deposited: 25 Jan 2007
Last modified: 15 Aug 2019 00:50

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Contributors

Author: N.D. Sandham ORCID iD
Author: C.L. Morfey
Author: Z.W. Hu

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