Numerical simulations of the flowfield and the noise generated by round nozzles are carried out and analyzed, with the twin goals of gaining insight into the flow features that are responsible for noise generation and of validating large-eddy simulation in as much depth as possible. The importance of including the nozzle internal flow, especially for complex geometries of interest, is emphasized. A two-step Reynolds-averaged Navier-Stokes/large-eddy simulation methodology is developed and applied to several nozzle geometries. Results from both Reynolds-averaged Navier-Stokes and large-eddy simulation computations are presented. The spectral predictions from large-eddy simulation are in good agreement with measured data, for a wide range of jet conditions. The upper limit on the Strouhal number for accurate spectral predictions is rising from about 2 to near 5 on the best grids. Further, the change in spectral shape with increasing angle in the aft quadrant, from a broad spectral peak to a narrower one, is captured by the simulations; in contrast, classical jet noise theories have failed in this regard. The locations and the nature of the noise sources are also obtained. Valuable insight is gained from the simulation of an unheated jet with a Mach number as low as 0.4. Contrary to some prevailing conceptions, there is beaming of directional radiation to aft angles, confined to inlet angles larger or equal about 150 deg, and the spectra within this radiation sector have the narrower peak, just as at higher Mach numbers. The results are most encouraging, and this study is a part of ongoing efforts to better understand the flow physics and possibly derive fresh ideas including for noise control from a broad visibility of the turbulence.
Comparisons between experiment and large-eddy simulation for jet noise
Vergleich zwischen Experiment und Großwirbelsimulationen für den Jet-Lärm
AIAA Journal (online) ; 45 , 8 ; 1952-1966
2007
15 Seiten, 26 Bilder, 1 Tabelle, 38 Quellen
Aufsatz (Zeitschrift)
Englisch
FLUID DYNAMICS - Comparisons Between Experiment and Large-Eddy Simulation for Jet Noise
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