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In-duct source identification of a blower using the near-field measurement
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.ORCID iD: 0000-0002-8474-8563
2014 (English)In: 21st International Congress on Sound and Vibration 2014, ICSV 2014, 2014, 2935-2941 p.Conference paper (Refereed)
Abstract [en]

The detailed information on the distribution of acoustic pressure and axial particle velocity at a source plane in a duct is useful for the low noise design of the source because it provides the position and strength of major noise sources. However, due to the limited spatial resolution of the conventional methods, the source behavior could not be observed in detail. In this work, a method to identify the pressure and axial velocity distribution at the source plane with high spatial resolution is suggested. Modal summation method including the evanescent waves is formulated, in which data can be provided from the near-field measurement. For the validation of the present method, the near-field array measurement in a duct excited by a blower is conducted. In the measurement of the nearfield and farfield acoustic pressures, the flush mounted microphone array is employed, and reference microphone technique using the cross correlation is adopted to suppress the turbulent flow noise. As a result, the measured near-field pressure is well restored with 26 evanescent modes, and the error between measured and restored pressure spectra is less than -20 dB in the Helmholtz number range of 0.57 < kR < 1.84. It is observed that the flush mounting measurement tends to over-estimate the pure radial modes, which results in the un- physical error in the predicted source parameters at the center of source plane. As a remedial ac-tion, pure radial modes are removed from the model that results in a successful reconstruction of the source distribution.

Place, publisher, year, edition, pages
2014. 2935-2941 p.
Keyword [en]
Acoustic noise, Blowers, Evanescent fields, Image resolution, Microphones, Restoration, Velocity control, Array measurements, Axial-velocity distribution, Conventional methods, High spatial resolution, Near-field measurement, Particle velocities, Source distribution, Source identification, Ducts
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:kth:diva-167898ScopusID: 2-s2.0-84922605817ISBN: 9781634392389OAI: diva2:820138
21st International Congress on Sound and Vibration 2014, ICSV 2014, 13 July 2014 through 17 July 2014

QC 20150611

Available from: 2015-06-11 Created: 2015-05-22 Last updated: 2015-06-11Bibliographically approved

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Bodén, Hans
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Linné Flow Center, FLOWMarcus Wallenberg Laboratory MWL
Fluid Mechanics and Acoustics

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