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Noise radiation from ducted fans with realistic duct-rotor coupling

Authors: F. Farassat; P. L. Spence;

Noise radiation from ducted fans with realistic duct-rotor coupling

Abstract

The problem of noise radiation from inlet and exhaust of ducted fans is important because of anticipated stringent noise standards. The aerodynamic and duct propagation problems of these engines have been solved. What is needed is the coupling of rotor aerodynamics and duct propagation using realistic physical and geometrical models on today’s high-speed computers. In this paper, a method is presented for prediction of noise from the inlet of ducted fans correctly accounting for fan blade aerodynamics. An Euler code is used giving the fluid dynamic parameters such as pressure and velocity at a duct section approximately one chord length from the fan face. Here, all of the pressure disturbance is propagating. This pressure disturbance is decomposed into spinning modes using Fourier and Hankel transforms in circumferential and radial directions, respectively. The amplitude of each mode is produced from interaction of upstream and downstream (due to reflections from the inlet) moving waves. The relative amplitudes of these waves are computed using a duct propagation code based on FEM by initializing the upstream moving wave of a given mode to unit amplitude and finding the reflection coefficients of all modes. A system of linear simultaneous equations for amplitudes of upstream and downstream moving waves is constructed and solved. From these amplitudes, the radiation from the duct inlet can be calculated. Computed examples of radiation from ducted fans in forward flight are presented.

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
1
Average
Average
Average
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