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Complex resonances and trapped modes in ducted domains

Duan, Yuting and Koch, Werner and Linton, Chris M. and McIver, Maureen (2007) Complex resonances and trapped modes in ducted domains. Journal of Fluid Mechanics, 571, pp. 119-147. Cambridge University Press. DOI: 10.1017/S0022112006003259.

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Abstract

Due to radiation losses, resonances in open systems are generally complex valued. However, near symmetric, centred objects in ducted domains, or in periodic arrays, so-called trapped modes can exist below the cut-off frequency of the first non-trivial duct mode. These trapped modes have no radiation loss and correspond to real-valued resonances. Above the first cut-off frequency isolated trapped modes exist only for specific parameter combinations. These isolated trapped modes are termed embedded, because their corresponding eigenvalues are embedded in the continuous spectrum of an appropriate differential operator. Trapped modes are of considerable importance in applications because at these parameters the system can be excited easily by external forcing. In the present paper directly computed embedded trapped modes are compared with numerically obtained resonances for several model configurations. Acoustic resonances are also computed in two-dimensional models of a butterfly and ball-type valve as examples of more complicated geometries.

Document Type:Article
Title:Complex resonances and trapped modes in ducted domains
Authors:
AuthorsInstitution or Email of Authors
Duan, YutingAgat Labs Ltd, Calgary, Canada
Koch, WernerUNSPECIFIED
Linton, Chris M.Loughborough University, Leics, UK
McIver, MaureenLoughborough University, Leics, UK
Date:2007
Journal or Publication Title:Journal of Fluid Mechanics
Refereed publication:Yes
In ISI Web of Science:Yes
Volume:571
DOI:10.1017/S0022112006003259
Page Range:pp. 119-147
Publisher:Cambridge University Press
Status:Published
Keywords:Acoustic resonances, trapped modes
HGF - Research field:other
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):other
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Helicopters
Deposited By: Elisabeth Winkels
Deposited On:06 Mar 2007
Last Modified:27 Apr 2009 13:30

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