Modal propagation angles in a cylindrical duct with flow and their relation to sound radiation

Rice, E. J.; Heidmann, M. F.; Sofrin, T. G.

doi:10.2514/6.1979-183

Cited by 69 publications

(60 citation statements)

References 10 publications

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“…One main advantage of such a model is that the duct mode radiation problem can be solved exactly by the Wiener-Hopf technique. These early works were later summarized and extended by Rice, Heidmann and Sofrin 45 to form a prediction formula for the direction of peak noise radiation. The most general formula of Rice et al was designed to be applicable to inlet radiation at static as well as at flight condition.…”

Section: Discussionmentioning

confidence: 99%

Physics of Acoustic Radiation from Jet Engine Inlets

Tam

Parrish

Envia

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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Numerical simulations of acoustic radiation from a jet engine inlet are performed using advanced computational aeroacoustics (CAA) algorithms and high-quality numerical boundary treatments. As a model of modern commercial jet engine inlets, the inlet geometry of the NASA Source Diagnostic Test (SDT) is used. Fan noise consists of tones and broadband sound. This investigation considers the radiation of tones associated with upstream propagating duct modes. The primary objective is to identify the dominant physical processes that determine the directivity of the radiated sound. Two such processes have been identified. They are acoustic diffraction and refraction. Diffraction is the natural tendency for an acoustic wave to follow a curved solid surface as it propagates. Refraction is the turning of the direction of propagation of sound waves by mean flow gradients. Parametric studies on the changes in the directivity of radiated sound due to variations in forward flight Mach number and duct mode frequency, azimuthal mode number, and radial mode number are carried out. It is found there is a significant difference in directivity for the radiation of the same duct mode from an engine inlet when operating in static condition and in forward flight. It will be shown that the large change in directivity is the result of the combined effects of diffraction and refraction.

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Section: Discussionmentioning

confidence: 99%

Physics of Acoustic Radiation from Jet Engine Inlets

Tam

Parrish

Envia

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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“…The high-vane counts result in the 1st BPF cut-off (Ref. 8), hence the very small tone levels measured at BPF as seen in Figures 5(a) and 7(a).…”

Section: Farfieldmentioning

confidence: 97%

The Advanced Noise Control Fan Baseline Measurements

McAllister

Loew

Lauer

et al. 2009

47th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…however, the importance of the inflow distortion contribution to fan noise will depend on the particular fan stage and inflow distortion structure. It is therefore of interest to theoretically study the fan noise due to inflow distortion interactions with a three -dimensional annular blade row and to compere the results of the theory to existing experimental data, This theoretical study provides the fan noise modal structure which is required for the prediction of far-field radiation patterns 2 , 3 and the design of acoustic suppressors where inflow distortion is the known source mechanism.4…”

Section: Analytical Modelmentioning

confidence: 99%