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Wave Modelling Techniques for Medium and High Frequency Vibroacoustic Analysis Including Porous Materials
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Numerical methods based on wave modelling are explored for the vibroacoustic analysis of wave propagation, sound transmission and interior noise in vehicles and buildings at medium and high frequencies. The presence of sound absorbing porous materials in practical engineering structures is also considered. The wave modelling techniques provide computational efficiency and physical insight, and two such methods having these advantages are developed in this thesis namely: the semi-analytical finite element method and the wave expansion method.

The semi-analytical finite element method is applicable to structures which have constant properties in one direction, and it uses a finite element discretization of the cross-section and analytical functions in the third direction. Equations of motion are derived from this method to study wave propagation characteristics, which help understand the vibroacoustic behavior of structures. These characteristics may also be used by high frequency techniques, such as statistical energy analysis. The wave propagation in sandwich panels with a poroelastic core, which is modeled with Biot's theory, is investigated thoroughly.

The semi-analytical finite element method retains the flexibility of the finite element method on geometry and also dramatically increases the computational speed thanks to the orthogonality of the analytical functions when used to calculate forced response. The calculated response of partitions is integrated into diffuse field sound transmission loss calculations of, for example, built-up train floor partitions and multilayer panels lined with porous materials. The calculations are computationally efficient and show good agreement with measurements, thus it is interesting for industrial optimizations.

The wave expansion method uses a priori defined plane wave solutions to the Helmholtz equation for approximation of the sound field in geometrically complex enclosures. It reduces the requirements regarding the number of degrees of freedom compared to the finite element method, which, furthermore, is polluted by dispersion errors. Therefore, the wave expansion method is particularly appealing for high frequency (or large wavenumber) calculations. Its application in interior sound field predictions is assessed within the automobile context.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , xvi, 46 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2014:51
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-151271ISBN: 978-91-7595-269-7 (print)OAI: oai:DiVA.org:kth-151271DiVA: diva2:747405
Public defence
2014-10-01, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 214909
Note

QC 20140916

Available from: 2014-09-17 Created: 2014-09-16 Last updated: 2014-09-17Bibliographically approved
List of papers
1. Wave propagation in sandwich panels with a poroelastic core
Open this publication in new window or tab >>Wave propagation in sandwich panels with a poroelastic core
2014 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 135, no 5, 2683-2693 p.Article in journal (Refereed) Published
Abstract [en]

Wave propagation in sandwich panels with a poroelastic core, which is modeled by Biot's theory, is investigated using the waveguide finite element method. A waveguide poroelastic element is developed based on a displacement-pressure weak form. The dispersion curves of the sandwich panel are first identified as propagating or evanescent waves by varying the damping in the panel, and wave characteristics are analyzed by examining their motions. The energy distributions are calculated to identify the dominant motions. Simplified analytical models are also devised to show the main physics of the corresponding waves. This wave propagation analysis provides insight into the vibro-acoustic behavior of sandwich panels lined with elastic porous materials.

Keyword
Finite-Element-Method, Sound-Transmission, Fluid, Motion, Equations, Guides, Plates, Formulations, Prediction, Media
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-147053 (URN)10.1121/1.4869090 (DOI)000336160000027 ()2-s2.0-84900430416 (Scopus ID)
Note

QC 20140624

Available from: 2014-06-24 Created: 2014-06-23 Last updated: 2017-12-05Bibliographically approved
2. Prediction of sound transmission through elastic porous material lined multilayer panels using a semi-analytical finite element method
Open this publication in new window or tab >>Prediction of sound transmission through elastic porous material lined multilayer panels using a semi-analytical finite element method
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-151300 (URN)
Note

QS 2014

Available from: 2014-09-17 Created: 2014-09-17 Last updated: 2014-09-17Bibliographically approved
3. Wave modelling in predictive vibro-acoustics: Applications to rail vehicles and aircraft
Open this publication in new window or tab >>Wave modelling in predictive vibro-acoustics: Applications to rail vehicles and aircraft
Show others...
2014 (English)In: Wave motion, ISSN 0165-2125, E-ISSN 1878-433X, Vol. 51, no 4, 635-649 p.Article in journal (Refereed) Published
Abstract [en]

Three different predictive methods based on wave descriptions of the acoustic field are presented and used to calculate transmission and radiation properties of typical rail and aerospace structures. First, a transfer matrix method assesses the sound transmission and wavenumbers of composite sandwich fuselage structures in a wide frequency range. The method is computationally effective and can be used for numerical optimization of sandwich lay-ups common in rail and aerospace engineering. Further, an approach for which a small finite element model of a periodic cell is applied to create a statistical model of a near periodic structure is shown to determine transmission and radiation properties of stiffened fuselage structures and an extruded train floor structure. Finally, a novel combination of the waveguide FE method with the Rayleigh-Ritz method is applied to: (i) calculate the transmission through a double wall structure; (ii) again assess the sound transmission of an extruded floor structure and also (iii) determine the sound pressure inside a large section of a rail car excited by external sound sources. All three methods presented can be used to effectively support decision making in the design process of trains and aircraft.

Keyword
Wave modelling, Finite element, Sound transmission, Sound radiation, Air-craft structure, Rail-car structure
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-146135 (URN)10.1016/j.wavemoti.2013.11.007 (DOI)000335609800009 ()2-s2.0-84898004644 (Scopus ID)
Note

QC 20140611

Available from: 2014-06-11 Created: 2014-06-09 Last updated: 2017-12-05Bibliographically approved
4. Prediction of sound field in geometrically complex enclosures with the wave expansion method
Open this publication in new window or tab >>Prediction of sound field in geometrically complex enclosures with the wave expansion method
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-151301 (URN)
Note

QS 2014

Available from: 2014-09-17 Created: 2014-09-17 Last updated: 2016-02-26Bibliographically approved

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