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In-duct identification of fluid-borne source with high spatial resolution
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.ORCID iD: 0000-0002-8474-8563
2014 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 333, no 23, 6074-6089 p.Article in journal (Refereed) Published
Abstract [en]

Source identification of acoustic characteristics of in-duct fluid machinery is required for coping with the fluid-borne noise. By knowing the acoustic pressure and particle velocity field at the source plane in detail, the sound generation mechanism of a fluid machine can be understood. The identified spatial distribution of the strength of major radiators would be useful for the low noise design. Conventional methods for measuring the source in a wide duct have not been very helpful in investigating the source properties in detail because their spatial resolution is improper for the design purpose. In this work, an inverse method to estimate the source parameters with a high spatial resolution is studied. The theoretical formulation including the evanescent modes and near-field measurement data is given for a wide duct. After validating the proposed method to a duct excited by an acoustic driver, an experiment on a duct system driven by an air blower is conducted in the presence of flow. A convergence test for the evanescent modes is performed to find the necessary number of modes to regenerate the measured pressure field precisely. By using the converged modal amplitudes, very-close near-field pressure to the source is regenerated and compared with the measured pressure, and the maximum error was -16.3 dB. The source parameters are restored from the converged modal amplitudes. Then, the distribution of source parameters on the driver and the blower is clearly revealed with a high spatial resolution for kR < 1.84 in which range only plane waves can propagate to far field in a duct. Measurement using a flush mounted sensor array is discussed, and the removal of pure radial modes in the modeling is suggested.

Place, publisher, year, edition, pages
2014. Vol. 333, no 23, 6074-6089 p.
Keyword [en]
Field Sensor Arrays, Ill-Posed Problems, Acoustic Properties, Inverse Methods, Flow, Modes, Fan, Decomposition, Strength
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:kth:diva-154364DOI: 10.1016/j.jsv.2014.07.005ISI: 000341675200012ScopusID: 2-s2.0-84926244752OAI: diva2:757119
3rd International Conference on Vibro-Impact Systems and Systems with Non-Smooth Interactions, JUL 23-27, 2013, Leinsweiler, Germany

QC 20141021

Available from: 2014-10-21 Created: 2014-10-20 Last updated: 2014-10-21Bibliographically approved

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