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Sound Radiation Properties of Complex Modes in Rectangular Plates: A Numerical Study

Unruh, Oliver and Sinapius, Michael and Monner, Hans Peter (2015) Sound Radiation Properties of Complex Modes in Rectangular Plates: A Numerical Study. Acta acustica united with Acustica. Hirtzel. ISSN 1610-1928 (In Press)

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Abstract

The sound radiation properties of real normal modes are often used to characterise acoustic sources such as vibrating plates. The assumption of homogeneously distributed structural damping is usually made and in consequence the eigenmodes are real. With the increasing use of high-performance composite structures and the demanding requirements for acoustic comfort, damping treatments such as constrained layer damping or embedded elastomer layers may be distributed locally at some critical locations of the vibrating structure. This violates the assumption of homogeneously distributed structural damping and results in complex mode shapes. In this case, dynamics of the vibrating systems within the resonances is no longer dominated by pure standing waves, but also by a superposition with travelling waves. This paper presents the results of a numerical study on sound radiation properties of this phenom-enon, generally known as complex modes of vibration. The finite element model of an inhomoge-neously damped plate is used to generate and investigate complex vibration patterns. The level of modal complexity of the generated complex modes is characterized by the modal collinearity index and the spatial distribution of the standing wave ratio. The fluid structure interaction is implemented by a elemental radiator approach and used for the acoustic characterisation of vibration patterns in terms of far-field radiation efficiencies and spatial distributions of sound intensity. It is shown that the eigenvector complexity can seriously affect the sound radiation properties of structural modes.

Item URL in elib:https://elib.dlr.de/92071/
Document Type:Article
Title:Sound Radiation Properties of Complex Modes in Rectangular Plates: A Numerical Study
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Unruh, OliverInstitut für Faserverbundleichtbau und Adaptronik - AdaptronikUNSPECIFIED
Sinapius, MichaelTU Braunschweig / DLR BraunschweigUNSPECIFIED
Monner, Hans PeterInstitut für Faserverbundleichtbau und Adaptronik - AdaptronikUNSPECIFIED
Date:January 2015
Journal or Publication Title:Acta acustica united with Acustica
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Publisher:Hirtzel
ISSN:1610-1928
Status:In Press
Keywords:Sound radiation, complex modes, inhomogeneous damping
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Structures and Materials
Location: Braunschweig
Institutes and Institutions:Institute of Composite Structures and Adaptive Systems > Adaptronics
Deposited By: Stanitzek, Silke
Deposited On:19 Nov 2014 08:38
Last Modified:06 Sep 2019 15:23

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