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Modelling strategies for thin imperfect interfaces and layers
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. LAUM UMR CNRS 6613, Le Mans Université, Le Mans, France.ORCID iD: 0000-0001-9071-6325
2019 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Stratégies de modélisation pour les interfaces et couches fines et imparfaites (French)
Abstract [en]

The global trend towards quieter environments has been one of the key topics of acoustics research for years. The recent tightening of the regulations on noise exposure as well as the many reports on the impact of noise on human health confirm this situation and stress ever more the need for innovative mitigation strategies. Numerous efforts from many teams allowed to refine existing solutions and explore new approaches towards a lower noise level ultimately leading to a number of promising concepts. Central to this field, the use of poroelastic media and the development of realistic meta-materials are paving the way to tackle the problem. In the meantime, a great part of the most widely adopted systems to mitigate noise, such as acoustics panels for instance, resort to thin resistive screens placed on the surface to protect the bulk and control the properties. Despite often being one of the thinnest components of the systems, they have a non-negligible impact on the overall response and are subject to a number of uncertainties.The approach chosen in this thesis differs from the global trend of designing new solutions and conversely relies on investigating the effect of uncertainties inherent to all these sound proofing systems. More precisely, the work performed focuses on modelling the impact of uncertain interfaces and uncertain parameters in the thin layers used as protective, tuning or aesthetic elements. These acoustic films, and to a certain extent the thin interface zones resulting from the assembly process, are notably challenging to characterise with precision. The main goal of this thesis is then to propose strategies to account for uncertainties on the parameters of the films and interfaces and predict their impact on the overall response of the systems.Three different scientific contributions are presented in this thesis. Together they discuss modelling aspects related to the films, propose possible simplifications and demonstrate the effect of parameter uncertainties. Finally they introduce numerical strategies to efficiently account for uncertainties in computations within the context of poroelastic and meta-poroelastic media.

Abstract [sv]

Den globala trenden mot allt tystare miljöer, har i flera år varit i fokus för forskningen inom teknisk akustik. Den senaste tidens skärpning av de reglementen som berör gränser för tillåten ljud- och bullerexponering, tillsammans med studier av bullers påverkan på hälsa, välbefinnande, inlärningsförmåga etc., understryker behovet av nya innovativa strategier. Dessa inbegriper som exempel förfining av redan existerande lösningar, utforskande av nya vägar till effektiva åtgärder för att uppnå en lägre ljudnivå, med flera. Stommen i de flesta åtgärder för att reducera ljudnivåer har sedan mitten av 1900-talet varit olika former av poroelastiska material och under de senaste decennierna även en utveckling av så kallade metamaterial, d.v.s. material vars egenskaper ej går att finna i naturen förekommande form, vilket även bereder väg för att finna nya lösningar på problemet. I dagsläget används, i de mest allmänt använda systemen för att reducera buller, till största delen tunna resistenta skikt som placeras på ytan för att skydda mot mekanisk påverkan och men även för att kunna kontrollera de akustiska egenskaperna. Trots att dessa ytskikt oftast är en av de tunnaste komponenterna i olika system, så är deras påverkan på det totala resultatet avsevärd och kan inte förbises. På grund av deras design, är tillverkningen ofta behäftad med bristande precision och de bidrar därför ofta till att de totala akustiska egenskaperna hos sammansatta system där de ingår, ofta uppvisar en spridning på grund av denna variation.I denna avhandling behandlas metoder för kunna undersöka effekten av dessa oundvikliga osäkerheter som finns i alla dessa ljudreducerande system. Mer precist, så har arbetet fokuserat på att modellera den påverkan som osäkerheten i gränsytorna och parametrarna i de tunna ytlagren innebär. Bland annat har arbetet varit inriktat på att hantera de utmaningar som ligger i att med precision karaktärisera de akustiska ytskikten och i viss utsträckning de tunna gränsytornas avskärmning som kommer av monteringsprocessen. Avhandlingens mål är att föreslå strategier för att ta i beaktande de osäkerheter hos filmens och gränsytornas parametrar för att förutse deras påverkan på det totala resultatet av systemet.Tre olika vetenskapliga bidrag presenteras i denna avhandling. Tillsammans behandlar de modelleringsaspekter relaterade till de tunna ytskikten, föreslår möjliga förenklingar och demonstrerar effekterna av osäkerheter i ingående modellparametrar. Slutligen introduceras numeriska strategier för att genom beräkningar, effektivt kunna beakta osäkerheterna gällande poroelastiska och meta-poroelastiska medier.

Abstract [fr]

La tendance globale poussant à développer des environnements plus calmes est, depuis des années, un des aspects clés de la recherche en acoustique. Le récent durcissement des régulations sur l'exposition au bruit ainsi que les nombreux rapports concernant son impact sur la santé humaine rappellent le besoin criant de stratégies innovante pour palier le problème. Le travail de nombreuses équipes a permis d'améliorer les solutions existantes et d'explorer de nouvelles approches, aboutissant à de nouveaux concepts prometteurs. L'utilisation de matériaux poroélastiques et  le développement de matériaux méta-poroélastiques réalistes sont un élément central de ces recherches et préfigurent des pistes viables pour résoudre le problème du bruit. En parallèle, une grande partie des systèmes courants pour le traitement des nuisances sonores, comme les panneaux acoustiques, utilisent de fins films résistifs placés en surface pour protéger les matériaux et contrôler le comportement acoustique du système. Malgré que ces films soient souvent les plus petits composants des panneaux, ils ont un impact non-négligeable sur la réponse globale et sont sujet à un certain nombre d'incertitudes.L'approche choisie dans cette thèse diffère de la tendance globale poussant au développement de nouveaux système. À l'inverse, ce travail s'emploie à modéliser l'impact des incertitudes concernant les films acoustiques et zones d'interface sur le comportement des absorbeurs et traitement acoustiques. Ces films et zones sont notoirement difficiles à caractériser avec précision à cause de leurs propriétés ou de de leur inaccessibilité. Le principal objectif de cette thèse est de proposer des stratégies pour prendre en compte les incertitudes et interfaces afin de prédire leur impact sur la réponse globale.Trois contributions scientifiques sont présentées. Ensemble, elle discutent différents aspects de modélisation se rapportant aux films et aux absorbeurs, proposent de possibles simplifications et mettent en lumière  l'effet des incertitudes. Finalement, ces contributions introduisent des stratégies au niveau du modèle ou du calcul pour prendre en compte les incertitudes dans le contexte des matériaux poroélastiques et méta-poroélastiques.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019.
Series
TRITA-SCI-FOU ; 2019:52
Series
NNT ; 2019LEMA1029
Keywords [en]
uncertainties, thin layers, numerical methods, simplified models, poroelastic materials
Keywords [fr]
incertitudes, couches fines, méthodes numeriques, modèles simplifiés, matériaux poroélastiques
Keywords [sv]
osäkerheter, tunna lager, numeriska metoder, förenklade modeller, poroelastiska medier
National Category
Fluid Mechanics and Acoustics Vehicle Engineering
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-263419ISBN: 978-91-7873-356-9 (print)ISBN: 978-91-7873-356-9 (electronic)OAI: oai:DiVA.org:kth-263419DiVA, id: diva2:1368261
Public defence
2019-12-13, F3, Lindstedtsvägen 26, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20191119

Available from: 2019-11-19 Created: 2019-11-06 Last updated: 2019-11-19Bibliographically approved
List of papers
1. A simplified model for thin acoustic screens
Open this publication in new window or tab >>A simplified model for thin acoustic screens
2018 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 144, no 1, p. EL76-EL81Article in journal (Refereed) Published
Abstract [en]

A generalization of the commonly used pressure jump modeling of thin porous layers is proposed. The starting point is a transfer matrix model of the layer derived using matrix exponentials. First order expansions of the propagating terms lead to a linear approximation of the associated phenomena and the resulting matrix is further simplified based on physical assumptions. As a consequence, the equivalent fluid parameters used in the model may be reduced to simpler expressions and the transfer matrix rendered sparser. The proposed model is validated for different backing conditions, from normal to grazing incidence and for a wide range of thin films. In the paper, the physical hypotheses are discussed, together with the origin of the field jumps.

Place, publisher, year, edition, pages
Acoustical Society of America (ASA), 2018
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-233427 (URN)10.1121/1.5047929 (DOI)000440810900013 ()30075680 (PubMedID)2-s2.0-85051036767 (Scopus ID)
Note

Correction in DOI:10.1121/1.5121612 ISI:000483887400062

QC 20180821

Available from: 2018-08-21 Created: 2018-08-21 Last updated: 2019-11-06Bibliographically approved
2. Erratum: A simplified model for thin acoustic screens [J. Acoust. Soc. Am. 144(1), EL76–EL81 (2018)]
Open this publication in new window or tab >>Erratum: A simplified model for thin acoustic screens [J. Acoust. Soc. Am. 144(1), EL76–EL81 (2018)]
2019 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 146, no 2, p. 1382-1383Article in journal (Refereed) Published
Abstract [en]

The present erratum reports an error impacting the figures of a contribution published in 2018 about a simplified model for thin acoustic screens in a transfer matrix context [Gaborit, Dazel, and Göransson (2018). J. Acoust. Soc. Am. 144(1), EL76–EL81]. A mistake in the implementation of the rigid termination condition for the systems under study is identified and a correct version is proposed along with the corrected figures. It is shown that this error does not impact the conclusions of the original contribution and that the model proposed therein keeps its advantages as the approximation error remains very similar to the previously reported values.

Place, publisher, year, edition, pages
Acoustical Society of America (ASA), 2019
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-263417 (URN)10.1121/1.5121612 (DOI)000483887400062 ()2-s2.0-85071579233 (Scopus ID)
Note

QC 20191106

Available from: 2019-11-06 Created: 2019-11-06 Last updated: 2019-11-11Bibliographically approved
3. Response envelope generation for thin acoustic screens with uncertain parameters
Open this publication in new window or tab >>Response envelope generation for thin acoustic screens with uncertain parameters
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-263418 (URN)
Note

QC 20191106

Available from: 2019-11-06 Created: 2019-11-06 Last updated: 2019-11-06Bibliographically approved
4. Coupling FEM, bloch waves and TMM in meta poroelastic laminates
Open this publication in new window or tab >>Coupling FEM, bloch waves and TMM in meta poroelastic laminates
Show others...
2018 (English)In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 104, no 2, p. 220-227Article in journal (Refereed) Published
Abstract [en]

The propagation of airborne plane waves in the presence of a meta poroelastic laminate, that is a poroelastic matrix coated with thin elastic layers at its facings and periodically-embedded with inclusions, is studied. Using the Finite Element Method (FEM) only would result in a drastic increase of the degrees of freedom due to the fine mesh required to account for the very thin coatings. Here, the approach relies on: The Bloch wave expansion of the fields in air; the modal Transfer Matrix Method to account for the coatings; and the coupling with the FEM model of the poroelastic matrix and the resonant inclusions. The model is developed for reflection and transmission problems and it can account for coatings with multiple layers. The procedure induces the addition of the Bloch coefficients in the FEM's linear system at a negligible additional computational cost. It is applied to the meta poroelastic laminates with poroelastic inclusions and rubber shell inclusions. The results are compared with those from the Multiple Scattering Theory and an excellent agreement between the methods is found. The approach offers a numerically-efficient way to account for coatings applied to meta poroelastic layers, and finds applications in industrial prototypes where coatings are widely used.

Place, publisher, year, edition, pages
S. Hirzel Verlag GmbH, 2018
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-224825 (URN)10.3813/AAA.919163 (DOI)000428258600005 ()2-s2.0-85043755972 (Scopus ID)
Note

QC 20180326

Available from: 2018-03-26 Created: 2018-03-26 Last updated: 2019-11-06Bibliographically approved

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