A Weak-Scattering Model for Turbine-Tone Haystacking outside the Cone of Silence

We consider the scattering of sound by turbulence in a jet shear layer. The turbulent, time-varying inhomogeneities in the flow scatter tonal sound fields in such a way as to give spectral broadening, which decreases the level of the incident tone, but increases the broadband level around the frequency of the tone. The scattering process is modelled for observers outside the cone of silence of the jet, using high-frequency asymptotic methods and a weak-scattering assumption. An analytical model for the far-field power spectral density of the scattered field is derived, and the result is compared to experimental data. The model correctly predicts the behaviour of the scattered field as a function of jet velocity and tone frequency.

[1]  C. L. Morfey,et al.  Developments in jet noise modelling—theoretical predictions and comparisons with measured data , 1976 .

[2]  L. M. B. C. Campos,et al.  The spectral broadening of sound by turbulent shear layers. Part 2. The spectral broadening of sound and aircraft noise , 1978, Journal of Fluid Mechanics.

[3]  R. Ewert.  Broadband slat noise prediction based on CAA and stochastic sound sources from a fast random particle-mesh (RPM) method , 2008 .

[4]  T. Tatsumi.  Theory of Homogeneous Turbulence , 1980 .

[5]  Roland Ewert,et al.  Spectral broadening of jet engine turbine tones , 2008 .

[6]  D. W. Schmidt,et al.  Experimental Study of Sound‐Wave Phase Fluctuations Caused by Turbulent Wakes , 1970 .

[7]  S. Clifford,et al.  Spectral broadening of an acoustic pulse propagating through turbulence , 1973 .

[8]  N. Bleistein,et al.  Asymptotic Expansions of Integrals , 1975 .

[9]  Jay C. Hardin,et al.  Stochastic Analysis of Spectral Broadening by a Free Turbulent Shear Layer , 1981 .

[10]  Sébastien Candel,et al.  Shielding and scattering by a jet flow , 1976 .

[11]  B. Tester,et al.  A weak scattering model for tone haystacking , 2009 .

[12]  R. A. Silverman,et al.  Wave Propagation in a Turbulent Medium , 1961 .

[13]  D. Mathews,et al.  Review of theory and methods for turbine noise prediction , 1975 .

[14]  Sébastien Candel,et al.  Radiation, refraction and scattering of acoustic waves in a free shear flow , 1976 .

[15]  C. Morfey,et al.  Developments in jet noise modeling - Theoretical predictions and comparisons with measured data , 1975 .

[16]  Richard A. Silverman,et al.  Wave Propagation in a Random Medium , 1960 .

[17]  L. M. B. C. Campos.  The spectral broadening of sound by turbulent shear layers. Part 1. The transmission of sound through turbulent shear layers , 1978 .

[18]  A. Cargill,et al.  Sound propagation through fluctuating flows - Its significance in aeroacoustics , 1983 .

[19]  Abbas Khavaran,et al.  On the Applicability of High-Frequency Approximations to Lilley's Equation , 2004 .

[20]  D. Mathews,et al.  Progress in core engine and turbine noise technology , 1974 .