Journal ArticleDOI
Aeroacoustics of hot jets
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In this article, the effect of jet temperature on the noise radiated by subsonic jets was quantified and it was concluded that the change in spectral shape at high jet temperatures, normally attributed to the contribution from dipoles, is due to Reynolds number effects and not dipoles.Abstract:
A systematic study has been undertaken to quantify the effect of jet temperature on the noise radiated by subsonic jets. Nozzles of different diameters were tested to uncover the effects of Reynolds number. All the tests were carried out at Boeing's Low Speed Aeroacoustic Facility, with simultaneous measurement of thrust and noise. It is concluded that the change in spectral shape at high jet temperatures, normally attributed to the contribution from dipoles, is due to Reynolds number effects and not dipoles. This effect has not been identified before. A critical value of the Reynolds number that would need to be maintained to avoid the effects associated with low Reynolds number has been estimated to be 400 000. It is well-known that large-scale structures are the dominant generators of noise in the peak radiation direction for high-speed jets. Experimental evidence is presented that shows the spectral shape at angles close to the jet axis from unheated low subsonic jets to be the same as from heated supersonic jets. A possible mechanism for the observed trend is proposed. When a subsonic jet is heated with the Mach number held constant, there is a broadening of the angular sector in which peak radiation occurs. Furthermore, there is a broadening of the spectral peak. Similar trends have been observed at supersonic Mach numbers. The spectral shapes in the forward quadrant and in the near-normal angles from unheated and heated subsonic jets also conform to the universal shape obtained from supersonic jet data. Just as for unheated jets, the peak frequency at angles close to the jet axis is independent of jet velocity as long as the acoustic Mach number is less than unity. The extensive database generated in the current test programme is intended to provide test cases with high-quality data that could be used for the evaluation of theoretical/semi-theoretical jet noise prediction methodologies.read more
Citations
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Journal ArticleDOI
Wave Packets and Turbulent Jet Noise
Peter Jordan,Tim Colonius +1 more
TL;DR: In this paper, the authors review evidence of the existence, energetics, dynamics, and acoustic efficiency of wave packets and highlight how extensive data available from simulations and modern measurement techniques can be used to distill acoustically relevant turbulent motions.
Journal ArticleDOI
The sources of jet noise: experimental evidence
TL;DR: In this article, four different approaches are used to determine experimentally the sources of jet mixing noise: spectral and directional information measured by a single microphone in the far field, fine-scale turbulence, large turbulence structures of the jet flow, and a mirror microphone is used to measure the noise source distribution along the lengths of high speed jets.
Journal ArticleDOI
Current Status of Jet Noise Predictions Using Large-Eddy Simulation
Daniel J. Bodony,Sanjiva K. Lele +1 more
TL;DR: A survey of the current applications of large-eddy simulation for the prediction of noise from single stream turbulent jets is given in this paper, with special attention paid to relationship between numerical and/or modeling choices and the prediction accuracy.
Journal ArticleDOI
On using large-eddy simulation for the prediction of noise from cold and heated turbulent jets
Daniel J. Bodony,Sanjiva K. Lele +1 more
TL;DR: The results of a series of large-eddy simulations of heated and unheated jets using approximately 106 grid points are presented in this article, where the authors show that the jets exhibit a faster centerline mean velocity decay rate relative to the existing data, with a corresponding 3-4'% over-prediction of the peak root-mean-square level.
Journal ArticleDOI
Unstructured Large-Eddy Simulations of Supersonic Jets
TL;DR: In this paper, experience gained from previous jet noise studies with the unstructured large-eddy simulation flow solver "Charles" is summarized and put to practice for the predictions of supersonic jets issued f...
References
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Proceedings ArticleDOI
On the Two Components of Turbulent Mixing Noise from Supersonic Jets
TL;DR: In this paper, two similarity spectra, one for the noise from the large turbulence structures/instability waves of the jet flow, the other for the fine-scale turbulence, are identified.
Journal ArticleDOI
Jet Mixing Noise from Fine-Scale Turbulence
TL;DR: In this paper, a semi-empirical theory is developed for the prediction of the spectrum, intensity, and directivity of the fine-scale turhulence noise from high-speed jets.
Journal ArticleDOI
An experimental study of jet noise part I: Turbulent mixing noise
TL;DR: In this paper, the characteristics of turbulent mixing noise in the far field from subsonic and fullyexpanded supersonic jet flows have been studied experimentally over an extensive envelope of jet operating conditions (jet exit velocity and temperature).
Journal ArticleDOI
Measurements of subsonic jet noise and comparison with theory
TL;DR: In this paper, measurements of the noise field from a 25 mm diameter subsonic air jet were analyzed in some detail by determining both the jet velocity dependence and the directivity of the intensity of the radiation in 1/3-octave bands at particular values of the frequency parameter, showing that the predicted variations overestimate the measurements and it appears that the convective amplification predicted by the theory is much reduced.
Journal ArticleDOI
Experimental investigation of density fluctuations in high-speed jets and correlation with generated noise
TL;DR: In this article, the air density fluctuations in the plumes of fully expanded, unheated free jets were investigated experimentally using a Rayleigh-scattering-based technique.