Impact of the source-correlation model in jet-noise prediction by acoustic analogy

Bassetti, A., Morfey, C.L. and Harper-Bourne, M. (2007) Impact of the source-correlation model in jet-noise prediction by acoustic analogy. 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), , Rome, Italy. 20 - 22 May 2007. 18 pp .

Abstract

For both Lilley and moving-frame Lighthill analogies the applied-stress equivalent source is given by the Reynolds stress. Previous jet-noise predictions based on the acoustic analogy adopted a frequency/wave-number source spectrum obtained by applying Fourier transform in space and time on an analytically suitable expression for the Reynolds-stress 2-point cross-correlation coefficient. Very few experimental data for the Reynolds-stress correlation are available in literature. Harper-Bourne has published a limited set of hot-wire measurements taken on a low-speed jet and corresponding to a single location on the nozzle lip line. In this paper a model for the 2-point correlation of the fluctuating Reynolds stress is introduced and compared to two previous correlation models and to the Harper-Bourne data. This shows to which extent the two-point correlation models can be adopted to t the turbulence measurements. The acoustic-source strength per unit volume is modelled in the frequency domain and broken down as product of different factors. The determination of these factors is performed by starting from some suitable 2-point correlation models including the model proposed here and one of the previous models. The output volumetric-strength spectra are used in turn as source master spectrum for a RANS-based jet-noise prediction. This shows the incidence of different correlation models on the estimation of isothermal 90-degree 1/3-octave jet-noise spectra.

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