Some remarks on source coherence affecting jet noise

Abstract The influence of axial and azimuthal source coherence on the noise radiation has been investigated. For jet noise at small Helmholtz numbers results of a theoretical source model have been compared with measured data. It is found from the noise data that the axial coherence length scales of the sound-radiating turbulence is excited artificially. Furthermore, are relatively large and do increase when the turbulence is excited artificially. Furthermore, the influence of the azimuthal source coherence length scale on the sound radiation from a source ring has been discussed. It is found that the sound field depends remarkably on the azimuthal source coherence, and that a completely incoherent source ring does not radiate sound. If the jet shear noise-source term is modelled, then in the source ring plane the second azimuthal sound component dominates at small Helmholtz numbers, as observed in jet experiments.

[1]  D. Ronneberger,et al.  Experiments on sound radiation due to non-linear interaction of instability waves in a turbulent jet , 1979 .

[2]  A. Michalke,et al.  An Expansion Scheme for the Noise from Circular Jets , 1971 .

[3]  H. S. Ribner,et al.  Perspectives on Jet Noise , 1981 .

[4]  I. S. Gradshteyn,et al.  Table of Integrals, Series, and Products , 1976 .

[5]  A. Michalke,et al.  On the effect of spatial source coherence on the radiation of jet noise , 1977 .

[6]  Erik Mollo-Christensen,et al.  Jet Noise and Shear Flow Instability Seen From an Experimenter’s Viewpoint , 1967 .

[7]  S. Crow,et al.  Orderly structure in jet turbulence , 1971, Journal of Fluid Mechanics.

[8]  M. Lighthill.  On sound generated aerodynamically II. Turbulence as a source of sound , 1954, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[9]  Helmut V. Fuchs,et al.  Coherent Structures in Jet Turbulence and Noise , 1977 .

[10]  Helmut V. Fuchs,et al.  Experimental Evidence of Turbulent Source Coherence Affecting Jet Noise , 1978 .

[11]  D. G. Crighton,et al.  Basic principles of aerodynamic noise generation , 1975 .

[12]  Michel Sunyach,et al.  Filtered azimuthal correlations in the acoustic far field of a subsonic jet , 1979 .

[13]  H. Fuchs,et al.  Turbulent source coherence and Helmholtz number as aerodynamic noise parameters , 1978 .

[14]  Michael Fisher,et al.  Correlation techniques and modal decomposition analysis for the detection of azimuthally coherent structures in jet flows , 1979 .

[15]  E. Mollo-Christensen,et al.  MEASUREMENTS OF NEAR FIELD PRESSURE OF SUBSONIC JETS , 1963 .

[16]  C. J. Moore.  The role of shear-layer instability waves in jet exhaust noise , 1977, Journal of Fluid Mechanics.

[17]  E. Pfizenmaier,et al.  On the amplification of broad band jet noise by a pure tone excitation , 1975 .

[18]  E. Pfizenmaier,et al.  The amplification of broadband jet noise by pure tone excitation , 1976 .

[19]  H. V. Fuchs,et al.  On turbulence and noise of an axisymmetric shear flow , 1975, Journal of Fluid Mechanics.