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  • 151.
    Seifzadeh, Alireza
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Pietrzyk, A.
    Volvo Cars Corporation, Gothenburg Sweden.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Ramakrishnan, R.
    Department of Architectural Science, Toronto Canada.
    Experimental investigation of coupling effects of passenger compartment and trunk of a car on coupled system natural frequencies using noise transfer function2014In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 83, p. 16-21Article in journal (Refereed)
    Abstract [en]

    The parcel shelf of a car has several holes for speakers and electrical devices. In addition, air ventilation holes are installed on the trim that covers the parcel shelf. The effect of the holes between the two cavities, passenger compartment and the trunk, and the natural frequencies of double cavities connected by the neck (parcel shelf) are very vital and useful to noise-vibration-harshness engineers, as the low frequency resonances contribute to the booming noise inside the car. In the present study, the coupling effect of the passenger compartment and the trunk connected through the holes on the parcel shelf in between, has been investigated experimentally using noise transfer function. The first and second coupled system modes are measured at around 40 Hz and 70-80 Hz respectively. By increasing the effective size of the holes on the parcel shelf, the first and second natural frequencies of coupled modes can be shifted to higher values. The current study has verified that holes act as point sources in the low frequency ranges. It was concluded that the coupled acoustic modes, in the low frequency range, are strongly controlled by fluid-structure interaction as well as changes in the panels mass and stiffness in the car interior space. The shift in the natural frequencies of connected cavities can be useful in the prediction of the interior noise in an automobile as well as provide a verification tool for conventional numerical techniques such as finite element methods.

  • 152.
    Semeniuk, Bradley
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. Centre for ECO2 Vehicle Design.
    Microstructure based estimation of the dynamic drag impedance of lightweight fibrous materials2017In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 141, no 3, p. 1360-1370Article in journal (Refereed)
    Abstract [en]

    This paper focusses on the prediction of one of the main mechanisms of acoustic attenuation, the dynamic drag impedance, of a bundle of fibres typical of lightweight fibrous porous materials. The methodology uses geometrical properties derived from microscopy, and is based on the assumption that the interaction between the shear stress fields of neighbouring fibres may be neglected in the predicted drag force of an individual fibre. An analytical procedure is discussed which provides an estimate of the drag forces acting on infinite longitudinal and transversely orientated cylinders oscillating sinusoidally in a viscous incompressible fluid of infinite extent, at rest. The frequency-dependent viscous drag forces are estimated from the shear stresses on the surface of the cylinders, and may be scaled in terms of fibre diameter distributions and orientation angles in order to predict the dynamic drag impedance of a real material. The range of validity for this modelling approach is assessed through finite element solutions of three different fibre arrangements.

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  • 153.
    Semeniuk, Bradley
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. Centre for ECO2 Vehicle Design.
    Modelling the Dynamic Viscous and Thermal Dissipation Mechanisms in a Fibrous Porous Material2018Conference paper (Other academic)
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  • 154.
    Semeniuk, Bradley
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Dazel, Olivier
    Université du Maine, Le Mans France.
    Dynamic equations of a transversely isotropic, highly porous, fibrous material including oscillatory heat transfer effects2019In: Journal of the Acoustical Society of America, ISSN 0001-4966, Vol. 146, no 4, p. 2540-2551Article in journal (Refereed)
    Abstract [en]

    The dynamic equations of a transversely isotropic fibrous, highly porous material are presented in terms of microstructure-derived analytical expressions for viscous dissipation, and analytical expressions for the oscillatory heat transfer between the thermal fields of the solid cylindrical glassfibres and the surrounding viscous fluid. This represents the non-equilibrium thermal expansion of the fluid, occurring when waves propagate in the porous material, and results in a frequency-dependent scaling of the fluid dilatation term. A state-space transfer matrix solution of the governing equations has been introduced, allowing the numerical acoustical performance of the fibrous material to be investigated, including the acoustical effects of heat transfer. In order to understand the dissipation mechanisms of the viscous and thermal boundary layers on the surface of the fibres and the validity of the assumptions made in the current model, a thermoviscous acoustic fluid finite element procedure has also been introduced. The results from these simulations illustrate the frequency-dependent interaction of the boundary layers between neighbouring fibres in the porous material.

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  • 155.
    Semeniuk, Bradley
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Dazel, Olivier
    Microstructure based modelling of the thermal and viscous dissipation of a transversely isotropic porous fibrous insulation material2018In: Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics, 2018, p. 697-711Conference paper (Refereed)
    Abstract [en]

    This paper focusses on the modelling and prediction of two of the main mechanisms of acoustic attenuation, the dynamic drag and thermal heat transfer, of a bundle of fibres typical of lightweight fibrous porous materials. The methodology uses geometrical properties derived from microscopy, and is based on the assumption that the interaction between the shear stress fields as well as the thermal fields of neighbouring fibres, may be neglected in the predicted dynamic impedances of an individual fibre. Analytical procedures are discussed which provide an estimation of the impedances acting on infinite longitudinal and transversely orientated cylinders. The frequency-dependent viscous and thermal contributions may be scaled in terms of statistical fibre diameter distributions and orientation angles. Using these analytical models, a three-dimensional poroelastic model of coupled acoustic and structural wave propagation through a transversely isotropic, fibrous, highly porous thermal insulation material is presented.

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  • 156.
    Semeniuk, Bradley
    et al.
    Rieter Automotive Managemnet AG, Switzerland.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Sound Radiated From Multilayer Trim Components2005In: Forum Acusticum Budapest 2005: 4th European Congress on Acustics, 2005, p. 117-122Conference paper (Refereed)
    Abstract [en]

    Lightweight porous acoustic multilayer trim components have traditionally been specified in terms of sound absorption and sound transmission loss performance targets. These targets are valid for airborne noise excitation only, in the medium to high frequency ranges. Unfortunately, this neglects the fact that in real-world vehicle applications, these components are also subjected to low-medium frequency structural vibration inputs from mechanical components, which is typically an acoustic sound radiation problem. Importantly, the material specification of the trim component developed only for absorption and sound transmission loss may be sub-optimal in terms of sound radiation behaviour. This then highlights the necessity for additional focus on this topic, especially from a numerical simulation perspective in the early stages of the sound proofing development process. The appropriate low-medium-high frequency acoustic performance balance can then be obtained. Simulation methods are now well established for predicting the absorption and sound transmission loss of multilayer trim components including lightweight porous materials and surfaces, but are less well developed for the prediction of the multilayer sound radiation problem.

  • 157.
    Stensson Trigell, Annika
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Wennhage, Per
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    ECO2 Vehicle Design: an initiative for a holistic perspective on future vehicle concepts2008Conference paper (Other academic)
  • 158.
    Tyskeng, Sara
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Wennhage, Per
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Ecological and economical Critera in Vehicle Design: Taking on the challenge2009In: Public Service Review: European Union, no 19Article in journal (Other (popular science, discussion, etc.))
  • 159.
    Tyskeng, Sara
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Jerrelind, Jenny
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Wennhage, Per
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Centre for ECO2 Vehicle Design: vehicle design research for more environmentally friendly and economically competitive vehicles2008In: The Vehicle Component, SVENartikelArticle in journal (Other (popular science, discussion, etc.))
  • 160.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Cuenca, Jacques
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    A method for characterisation of the static elastic properties of the porous frame of orthotropic open-cell foams2015In: International Journal of Engineering Science, ISSN 0020-7225, E-ISSN 1879-2197, Vol. 86, p. 44-59Article in journal (Refereed)
    Abstract [en]

    This paper proposes a method to identify the static, fully relaxed elastic Hooke's matrix of a porous open-cell material. The moduli are estimated through an inverse estimation method, by performing a fit of a numerical model on the measured displacements on the faces of the porous material. These displacements are obtained from a static compression along each of the three coordinate axes. The material is modelled as an orthotropic equivalent solid, of which the principal directions are not necessarily aligned with the orthonormal coordinate system in which the experiments are conducted. The angles of relative orientation accounting for the misalignment are among the properties to be estimated. The focus in this paper is on the methodology itself, and its validity is verified by applying the method to four artificial materials with different levels of anisotropy. In addition, the robustness of the method to perturbations on the input data is investigated.

  • 161.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Cuenca, Jacques
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    A method for inverse estimation of the static elastic properties of anisotropic poroelastic foams - with application to a melamine foam2013Report (Refereed)
    Abstract [en]

    The paper presents a method for the characterisation of the static, fully relaxed elastic properties of poroelastic materials. The approach is based on full field measurements of the 3D displacements in a number of points on the faces of the compressed material sample. These are used as targets in an inverse estimation to fit a model of the material to experimental data. In the current work, the material is modelled as an orthotropic equivalent solid, of which the principal directions are not necessarily aligned with the orthonormal coordinate system in which the experiments are conducted. The angles of relative orientation accounting for the misalignment are among the properties to be estimated. In addition, the proposed model considers the region of reduced stiffness close to material discontinuities, which has been identified in previous investigations. The method presented is verified for an artificial material, and its robustness is studied. A characterised melamine foam is found to have an orthotropic symmetry, and its lowest stiffness in the direction parallel to the rise direction of the material.

  • 162.
    Van Der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Ultrasound.
    Cuenca, Jacques
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Ultrasound.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Ultrasound.
    A method for the inverse estimation of the static elastic compressional moduli of anisotropic poroelastic foams-With application to a melamine foam2015In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 43, p. 123-130Article in journal (Refereed)
    Abstract [en]

    This paper presents the application of a method for the characterisation of the static, fully relaxed elastic properties of poroelastic materials. The approach is based on full field measurements of the 3D displacements in a number of points on the faces of the compressed material sample. These are used as targets in an inverse estimation to fit a model of the material to the experimental data. The material is modelled as an orthotropic equivalent solid, whose principal directions are not necessarily aligned with the coordinate system in which the experiments are conducted. The angles of relative orientation accounting for the potential misalignment are estimated, together with the elastic moduli of the material. In addition, the proposed model considers the region of reduced stiffness close to material discontinuities, which has been identified in previous investigations. The method is applied to a melamine foam, which is found to have its lowest stiffness in the direction parallel to the rise direction of the material. © 2015 Elsevier Ltd All rights reserved.

  • 163.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Identification of the full anisotropic flow resistivity tensor for multiple glass wool and melamine foam samples2013In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 134, no 6, p. 4659-4669Article in journal (Refereed)
    Abstract [en]

    The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of the most important material properties for the acoustic performance of porous materials used in acoustic treatments. Due to the manufacturing processes involved, these porous materials are most often geometrically anisotropic on a microscopic scale, and for demanding applications, there is a need for improved characterization methods. This paper discusses recent refinements of a method for the identification of the anisotropic flow resistivity tensor. The inverse estimation is verified for three fictitious materials with different degrees of anisotropy. Measurements are performed on nine glass wool samples and seven melamine foam samples, and the anisotropic flow resistivity tensors obtained are validated by comparison to measurements performed on uni-directional cylindrical samples, extracted from the same, previously measured cubic samples. The variability of flow resistivity in the batch of material from which the glass wool is extracted is discussed. The results for the melamine foam suggest that there is a relation between the direction of highest flow resistivity, and the rise direction of the material.

  • 164.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Inverse estimation of static flow resistivity in porous materials: discussion of the method and results for two tested porous materials2011Conference paper (Other academic)
    Abstract [en]

    Porous materials are widely used in applications which focus on noise andvibration control. Their thermal, mechanical and acoustical properties arebenecial for the use of these materials in aeronautical and vehicle industries.Standard measurements for the characterization of porous materials exist andare carried out in many laboratories worldwide. However, these measurementsdo not always consider the possible anisotropy, present in porous materials.The production process of porous materials introduces an inherent geometricanisotropy in the material at micro scale, which in uences the materialproperties at macro scale. It has been shown by Khurana et al. [3] thatthe anisotropy can have a signicant in uence on the acoustical behaviourof the material, especially if the angle of incidence is increased. One ofthe macroscopic parameters, which is important for the performance ofthese material in acoustical applications, is the static ow resistivity. Themethodology to measure the ow resistivity in porous materials is described inISO 9053 [2], giving the ow resistivity of a porous material along one direction.These unidirectional measurements do not allow for a full characterization ofthe ow resistivity tensor, and hence a proper characterization of the porousmaterial. The identication method developed by Goransson et al. [1] providesa non-destructive measurement method to determine the static ow resistivitytensor. The method is based on an inverse estimation of the measured pressure drops over a cubic material sample.The method as described in the work of Goransson et al. [1] has beenimproved in several ways. The Globally Convergent Method of MovingAsymptotes (GCMMA) [5] , which assures convergence, has replaced theMethod of Moving Asymptotes (MMA) [4]. Secondly, the approach of inverseestimation has been veried for a wide range of anisotropy, by setting articialand a priori known anisotropic ow resistivity tensors as a target in theestimation. Furthermore, another approach towards the problem has beentested, in which the focus is on the eigenvalues and eigenvectors of the tensor,in stead of the independent components. In addition, a more precise descriptionof the errors will be presented as well as an error estimation.This method for identication of the anisotropic ow resistivity tensorhas been applied to two dierent porous materials, a brous glass wool anda Melamine foam. The two materials are expected to show dierent degreesof anisotropy with respect to ow resistivity. Glass wool is assumed to betransversely isotropic while the level of anisotropy of Melamine is not asobvious. The full anisotropic ow resistivity tensors of the tested glass wooland Melamine samples are presented, together with their principal valuesand directions. The eigenvalue decomposition provides an insight into theconnection between the directionality of the ow resistivity in each material,and its production process. The overall approach of the method is validated bycomparing the estimated ow resistivity tensors to the ow resistivity measuredin cylindrical samples extracted from the cubic samples tested. Furthermore, astudy of the homogeneity in density and ow resistivity for the two materialsshows that these properties vary within the block of material.References[1] P. Goransson, R. Guastavino, and N. E. Horlin. Measurement and inverseestimation of 3D anisotropic ow resistivity for porous materials.Journalof Sound and Vibration, 327:354{367, 2009.[2] ISO 9053:1991: Acoustics { materials for acoustical applications {determination of air ow resistance, 1991.[3] P. Khurana, L. Boeckx, W. Lauriks, P. Leclaire, O. Dazel, and J.F. Allard.A description of transversely isotropic sound absorbing porous materials bytransfer matrices.Journal of the Acoustical Society of America, 125:915{921,2008.[4] K. Svanberg. The method of moving asymptotes - a new method forstructural optimization.International Journal for Numerical methods inEngineering, 24:359{373, 1987.

  • 165.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Measurement and Inverse Estimation of the Full Anisotropic Flow Resistivity Tensor of Melamine Foam2010Report (Other academic)
    Abstract [en]

    The flow resistivity tensor, which is the inverse of the viscous per- meability tensor, is one of the most important material properties for the acoustic performance of open cell foams used in acoustic treatments. Due to the manufacturing processes, these foams are most often geomet- rically anisotropic on a microscopic scale. For such a materials there is a need for improved characterisation methods, and this paper discusses the estimation of the flow resistivity tensor of Melamine samples using a methodology which is an improvement of a method previously published by Go ̈ransson et al. The validity of the new method is in addition ver- ified for a wider range of anisotropy. Measurements are performed on cubic Melamine samples, and the resulting 3D flow resistivity tensors are presented. The anisotropic flow resistivity tensors are validated by com- parison to measurements performed on uni-directional cylindrical samples extracted from the previously measured cubic samples. The results sug- gest that there is a relation between the direction of highest flow resistivity, and the rise direction of the material.

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    paper A
  • 166.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Inverse Estimation of the Flow Resistivity Tensor of Open-Cell Foams from Experimental Data and Darcy’s Flow Simulations2010In: Proceedings of the COMSOL Conference 2010, 2010Conference paper (Other academic)
    Abstract [en]

    The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of the most important material properties for the acoustic performance of open cell foams, used in acoustic treatments. Due to the manufacturing processes, these foams are most often geometrically anisotropic. This paper discusses the estimation of the flow resistivity tensor using an improvement of a previously published method by Göransson, Guastavino et al. First, flow measurements were performed for different orientations of a cubic porous sample. The modelling of the flow resistivity tensor is centred around a three-dimensional Darcy\'s law model in COMSOL Earth Science Module, representing the experimental set up. The simulations are performed within an optimization loop, to determine which flow resistivity tensor gives the best fit of the simulation results to the experimental data, of volume flow and pressure drop between the inlets and outlets. The discussion focuses on the optimiser, the use of COMSOL Multiphysics and the identified flow resistivity tensor of a Melamine sample.

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    COMSOL_2010_VdK
  • 167.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Measurement and Inverse Estimation of the Full Anisotropic Flow Resistivity Tensor of Glass Wool2010Report (Other academic)
    Abstract [en]

    The air flow resistivity of nine adjacent glass wool samples is measured and estimated using a previously published method. The samples are extracted from a large slab of glass wool material. Identifying the full flow resistivity tensors for nine adjacent cubic glass wool samples allows for an estimation of the spatial distribution of normal and planar flow resistivity throughout the measured material. The average density of the samples tested is 27.8 kg/m3. The estimated flow resistivity tensors are validated by comparison to uni-directional measurements on cylindrical samples, extracted from the cubic glass wool samples tested. Furthermore, the uni-directional measurement method is studied, providing useful insights on the effect of sample thickness on the measured flow resistivity for an anisotropic material.

  • 168.
    Van der Kelen, Christophe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Pluymers, Bert
    Department of Mechanical Engineering, Katholieke Universiteit Leuven, Heverlee, Belgium.
    Desmet, Wim
    Department of Mechanical Engineering, Katholieke Universiteit Leuven, Heverlee, Belgium.
    On the influence of frequency-dependent elastic properties in vibro-acoustic modelling of porous materials under structural excitation2014In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 333, no 24, p. 6560-6571Article in journal (Refereed)
    Abstract [en]

    The aspects related to the frequency dependence of the elastic properties of porous materials have been largely neglected in the past for several reasons. For acoustic excitation of porous materials, the material behaviour can be quite well represented by models where the properties of the solid frame have little influence. Only recently has the importance of the dynamic moduli of the frame come into focus. This is related to a growing interest in the material behaviour due to structural excitation. Two aspects stand out in connection with the elastic-dynamic behaviour. The first is related to methods for the characterisation of the dynamic moduli of porous materials. The second is a perceived lack of numerical methods able to model the complex material behaviour under structural excitation, in particular at higher frequencies. In the current paper, experimental data from a panel under structural excitation, coated with a porous material, is used in correlation with numerical predictions, involving a frequency-dependent material model for the stiffness properties of the porous material. The results suggest that the frequency dependence is of importance for a correct prediction of the response of trim installations. The change in material behaviour due to the frequency-dependent properties is illustrated in terms of the propagation of the slow wave and the shear wave in the porous material.

  • 169.
    Östberg, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    On cylindrical waves in anisotropic Cartesian materials and its implications on the harmonic mode separability assumption2011Conference paper (Other academic)
  • 170.
    Östberg, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
    Prediction of noise transmission through anisotropic multilayered aircraft fuselage, using finite element models including porous, elastic and fluid domains2010Conference paper (Refereed)
    Abstract [en]

    Prediction of noise transmission through anisotropic multilayered aircraft fuselage, using finite element models including porous, elastic and fluid domains is carried out. A passenger aircraft carrier is modelled using a novel finite element formulation, utilising the rotationally symmetric geometry in order to greatly reduce the computational cost. The model consists of anisotropic porous, elastic and fluid domains. The axi-symmetry of the structure allows for the use of analytical functions describing the wave propagation in the circumferential spatial directions, and thus reducing the number of required finite elements considerably. It is found that a fairly limited number of modes are required to satisfactorily describe the sound fields.

  • 171.
    Östberg, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Hörlin, Nils
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Weak forms for modelling of rotationally symmetric, multilayered structures, including anisotropic poro-elastic media2012In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 90, no 8, p. 1035-1052Article in journal (Refereed)
    Abstract [en]

    A weak form of the anisotropic Biot's equation represented in a cylindrical coordinate system using a spatial Fourier expansion in the circumferential direction is presented. The original three dimensional Cartesian anisotropic weak formulation is rewritten in an arbitrary orthogonal curvilinear basis. Introducing a cylindrical coordinate system and expanding the circumferential wave propagation in terms of orthogonal harmonic functions, the original, geometrically rotationally symmetric three dimensional boundary value problem, is decomposed into independent two-dimensional problems, one for each harmonic function. Using a minimum number of dependent variables, pore pressure and frame displacement, a computationally efficient procedure for vibro-acoustic finite element modelling of rotationally symmetric three-dimensional multilayered structures including anisotropic porous elastic materials is thus obtained. By numerical simulations, this method is compared with, and the correctness is verified against, a full three-dimensional Cartesian coordinate system finite element model.

  • 172.
    Östberg, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hörlin, Nils-Erik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Weak formulation of Biot's equations in cylindrical coordinates with harmonic expansion in the circumferential direction2010In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 81, no 11, p. 1439-1454Article in journal (Refereed)
    Abstract [en]

    A weak symmetric form of Biot's equation in cylindrical coordinates with a spatial Fourier expansion in the circumferential direction is presented. The solid phase displacement and the pore pressure are used as the dependent variables. The original three-dimensional boundary value problem is here, due to the orthogonality of the harmonic functions and the rotationally symmetric geometry, decomposed into independent two-dimensional problems, one for each harmonic function. This formulation provides a computationally efficient procedure for vibroacoustic finite element modelling of rotationally symmetric three-dimensional multilayered structures including porous elastic materials. By numerical Simulations, this method is compared with, and verified against, full three-dimensional Cartesian coordinate system finite element models.

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