In-duct identification of a rotating sound source with high spatial resolution

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To understand and reduce the flow noise generation from in-duct fluid machines, it is necessary to identify the acoustic source characteristics precisely. In this work, a source identification technique, which can identify the strengths and positions of the major sound radiators in the source plane, is studied for an in-duct rotating source. A linear acoustic theory including the effects of evanescent modes and source rotation is formulated based on the modal summation method, which is the underlying theory for the inverse source reconstruction. A validation experiment is conducted on a duct system excited by a loudspeaker in static and rotating conditions, with two different speeds, in the absence of flow. Due to the source rotation, the measured pressure spectra reveal the Doppler effect, and the amount of frequency shift corresponds to the multiplication of the circumferential mode order and the rotation speed. Amplitudes of participating modes are estimated at the shifted frequencies in the stationary reference frame, and the modal amplitude set including the effect of source rotation is collected to investigate the source behavior in the rotating reference frame. By using the estimated modal amplitudes, the near-field pressure is re-calculated and compared with the measured pressure. The obtained maximum relative error is about -25 and -10 dB for rotation speeds at 300 and 600 rev/mm, respectively. The spatial distribution of acoustic source parameters is restored from the estimated modal amplitude set. The result clearly shows that the position and magnitude of the main sound source can be identified with high spatial resolution in the rotating reference frame.
Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Issue Date
2015-11
Language
English
Article Type
Article
Keywords

NOISE SOURCES; CONVECTIVE AMPLIFICATION; INVERSE METHODS; FLUID MACHINES; FIELD; RECONSTRUCTION; DECOMPOSITION; HOLOGRAPHY; STRENGTH; TURBINE

Citation

JOURNAL OF SOUND AND VIBRATION, v.357, pp.51 - 73

ISSN
0022-460X
DOI
10.1016/j.jsv.2015.07.015
URI
http://hdl.handle.net/10203/203837
Appears in Collection
ME-Journal Papers(저널논문)
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