Turbulences as sound sources

Seppo Uosukainen

Research output: Book/ReportReportProfessional

Abstract

The aerodynamic sound source of a turbulent flow with a high Reynolds' number is composed of two types of Reynolds' stress components containing turbulent vortices as elements: perturbation-perturbation solenoidal velocity interaction (self-noise) and perturbation-static velocity interaction (shear-noise). The vortices act as quadrupole sources. Near a scattering surface, a high turbulent velocity imparts high fluctuating forces to it and couples to sound causing the scattered sound to be even stronger than the original one. The high-Reynolds'-number subsonic cold-air jet structure, beginning from a nozzle and developing gradually to solenoidal and turbulent, consists of a mixing region, a transition region, and a fully developed region. Most of the sound power originates from the mixing region. The spectrum of the jet noise is of broadband character. The typical radiation pattern of a quadrupole distribution is totally masked by convectional effects of the jet flow, which tend to enhance the sound greatly in the flow direction. The sound propagating in the jet flow direction will be refracted sidewards, causing a cone centered on the downstream jet axis wherein the far field sound is greatly reduced (zone of silence), and tending to decline the lobe of the radiation pattern. When a flow attacks a plate parallel to its surface at Reynolds' numbers high enough, there begins to form unsteady vortices, forming a turbulent boundary layer. The wavenumber spectrum in the turbulent boundary layer has two maxima: the convective peak at a high subsonic wavenumber and the sonic peak at the acoustic wavenumber. The sonic and supersonic spectral components at the surface generate active propagating sound, most of the acoustic energy propagating at grazing incidence downstream. Downstream propagating sound due to the wavenumber components near the sonic peak refracts towards the surface, and upstream propagating sound refracts outwards from the surface, enhancing the sonic peak in the downstream radiation and possibly eliminating it in the upstream radiation. The convective peak at the surface leads to the hydrodynamic coincidence, causing sound transmission and radiation at frequencies below the hydrodynamic coincidence frequency.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages47
ISBN (Electronic)951-38-6258-5
ISBN (Print)951-38-6257-7
Publication statusPublished - 2003
MoE publication typeD4 Published development or research report or study

Publication series

NameVTT Publications
PublisherVTT
No.513
ISSN (Print)1235-0621
ISSN (Electronic)1455-0849

Fingerprint

turbulence
acoustics
high Reynolds number
radiation
jet flow
turbulent boundary layer
vortices
perturbation
upstream
quadrupoles
hydrodynamics
jet aircraft noise
air jets
sound transmission
Reynolds stress
parallel plates
grazing incidence
aerodynamics
lobes
turbulent flow

Keywords

  • noise
  • jet noise
  • turbulence
  • turbulent flow
  • vortex flow
  • air jets
  • Reynolds' stress
  • boundary layers

Cite this

Uosukainen, S. (2003). Turbulences as sound sources. Espoo: VTT Technical Research Centre of Finland. VTT Publications, No. 513
Uosukainen, Seppo. / Turbulences as sound sources. Espoo : VTT Technical Research Centre of Finland, 2003. 47 p. (VTT Publications; No. 513).
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Uosukainen, S 2003, Turbulences as sound sources. VTT Publications, no. 513, VTT Technical Research Centre of Finland, Espoo.

Turbulences as sound sources. / Uosukainen, Seppo.

Espoo : VTT Technical Research Centre of Finland, 2003. 47 p. (VTT Publications; No. 513).

Research output: Book/ReportReportProfessional

TY - BOOK

T1 - Turbulences as sound sources

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N1 - Project code: R2SU00573

PY - 2003

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N2 - The aerodynamic sound source of a turbulent flow with a high Reynolds' number is composed of two types of Reynolds' stress components containing turbulent vortices as elements: perturbation-perturbation solenoidal velocity interaction (self-noise) and perturbation-static velocity interaction (shear-noise). The vortices act as quadrupole sources. Near a scattering surface, a high turbulent velocity imparts high fluctuating forces to it and couples to sound causing the scattered sound to be even stronger than the original one. The high-Reynolds'-number subsonic cold-air jet structure, beginning from a nozzle and developing gradually to solenoidal and turbulent, consists of a mixing region, a transition region, and a fully developed region. Most of the sound power originates from the mixing region. The spectrum of the jet noise is of broadband character. The typical radiation pattern of a quadrupole distribution is totally masked by convectional effects of the jet flow, which tend to enhance the sound greatly in the flow direction. The sound propagating in the jet flow direction will be refracted sidewards, causing a cone centered on the downstream jet axis wherein the far field sound is greatly reduced (zone of silence), and tending to decline the lobe of the radiation pattern. When a flow attacks a plate parallel to its surface at Reynolds' numbers high enough, there begins to form unsteady vortices, forming a turbulent boundary layer. The wavenumber spectrum in the turbulent boundary layer has two maxima: the convective peak at a high subsonic wavenumber and the sonic peak at the acoustic wavenumber. The sonic and supersonic spectral components at the surface generate active propagating sound, most of the acoustic energy propagating at grazing incidence downstream. Downstream propagating sound due to the wavenumber components near the sonic peak refracts towards the surface, and upstream propagating sound refracts outwards from the surface, enhancing the sonic peak in the downstream radiation and possibly eliminating it in the upstream radiation. The convective peak at the surface leads to the hydrodynamic coincidence, causing sound transmission and radiation at frequencies below the hydrodynamic coincidence frequency.

AB - The aerodynamic sound source of a turbulent flow with a high Reynolds' number is composed of two types of Reynolds' stress components containing turbulent vortices as elements: perturbation-perturbation solenoidal velocity interaction (self-noise) and perturbation-static velocity interaction (shear-noise). The vortices act as quadrupole sources. Near a scattering surface, a high turbulent velocity imparts high fluctuating forces to it and couples to sound causing the scattered sound to be even stronger than the original one. The high-Reynolds'-number subsonic cold-air jet structure, beginning from a nozzle and developing gradually to solenoidal and turbulent, consists of a mixing region, a transition region, and a fully developed region. Most of the sound power originates from the mixing region. The spectrum of the jet noise is of broadband character. The typical radiation pattern of a quadrupole distribution is totally masked by convectional effects of the jet flow, which tend to enhance the sound greatly in the flow direction. The sound propagating in the jet flow direction will be refracted sidewards, causing a cone centered on the downstream jet axis wherein the far field sound is greatly reduced (zone of silence), and tending to decline the lobe of the radiation pattern. When a flow attacks a plate parallel to its surface at Reynolds' numbers high enough, there begins to form unsteady vortices, forming a turbulent boundary layer. The wavenumber spectrum in the turbulent boundary layer has two maxima: the convective peak at a high subsonic wavenumber and the sonic peak at the acoustic wavenumber. The sonic and supersonic spectral components at the surface generate active propagating sound, most of the acoustic energy propagating at grazing incidence downstream. Downstream propagating sound due to the wavenumber components near the sonic peak refracts towards the surface, and upstream propagating sound refracts outwards from the surface, enhancing the sonic peak in the downstream radiation and possibly eliminating it in the upstream radiation. The convective peak at the surface leads to the hydrodynamic coincidence, causing sound transmission and radiation at frequencies below the hydrodynamic coincidence frequency.

KW - noise

KW - jet noise

KW - turbulence

KW - turbulent flow

KW - vortex flow

KW - air jets

KW - Reynolds' stress

KW - boundary layers

M3 - Report

SN - 951-38-6257-7

T3 - VTT Publications

BT - Turbulences as sound sources

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Uosukainen S. Turbulences as sound sources. Espoo: VTT Technical Research Centre of Finland, 2003. 47 p. (VTT Publications; No. 513).