MEASUREMENTS OF NOISE RADIATED BY SUBSONIC AIR JETS

Abstract

The spectrum of the acoustic power radiated by turbulent air jets issuing from two nozzles of different diameters was determined over a range of subsonic flow speeds. Results, presented in dimensionless form, show substantial agreement with Lighthill's theory of turbulence noise which predicts that the ratio of radiated acoustic energy to expended mechanical energy is proportional to the fifth power of the Mach number with only minor dependence upon the Reynolds number. The factor of proportionality was determined to be of the order of 0.0002. This means that for any given jet the total radiated acoustic power is approximately proportional to the eighth power of the jet flow velocity. The spectrum exhibits a broad peak, whose frequency appears to be determined by the thickness of the shear layer and the sonic velocity (rather than the flow velocity) but the evidence is not conclusive.

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Document Details

Document Type
Technical Report
Publication Date
Nov 01, 1952
Accession Number
AD0650175

Entities

People

  • H. M. Fitzpatrick
  • R. Lee

Tags

Communities of Interest

  • Energy and Power Technologies
  • Weapons Technologies

DTIC Thesaurus Topics

  • Acoustic Measurement
  • Acoustic Properties
  • Acoustics
  • Air Flow
  • Electronics Laboratories
  • Fluid Dynamics
  • Fluid Flow
  • Fluid Mechanics
  • Hydrodynamics
  • Measurement
  • Mechanical Properties
  • Mechanics
  • Model Basins
  • Physics Laboratories
  • Reynolds Number
  • Sound Pressure
  • Turbulent Mixing

Fields of Study

  • Physics

Readers

  • Acoustics.
  • Atmospheric Science / Meteorology, specifically Wind Wave Turbulence.
  • Combustion and Flow Dynamics.