Acoustic response of fibrous absorbent materials to impulsive transient excitations

Payri, F.; Broatch, A.; Salavert, José Miguel; Moreno, D.

doi:10.1016/j.jsv.2009.10.015

Cited by 5 publications

(3 citation statements)

References 25 publications

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“…E glass fibre is considered in the calculations, whose coefficients are 1 = 5.774 and 2 = 1.792, thus providing a resistivity = 30716 rayl/m for = 120 kg/m 3 [23]. The bulk density is usually considered constant in the bibliography [11,16,[18][19][20][21][22][23][24][25]. Heterogeneities can appear, however, due to the silencer manufacturing process, leading to spatial variations of the bulk density and material resistivity [1][2][3][4].…”

Section: Acoustic Model Of the Materials Heterogeneity Due To Densitymentioning

confidence: 99%

3D Acoustic Modelling of Dissipative Silencers with Nonhomogeneous Properties and Mean Flow

Sánchez-Orgaz

Denia

Martínez‐Casas

et al. 2014

Advances in Mechanical Engineering

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A finite element approach is proposed for the acoustic analysis of automotive silencers including a perforated duct with uniform axial mean flow and an outer chamber with heterogeneous absorbent material. This material can be characterized by means of its equivalent acoustic properties, considered coordinate-dependent via the introduction of a heterogeneous bulk density, and the corresponding material airflow resistivity variations. An approach has been implemented to solve the pressure wave equation for a nonmoving heterogeneous medium, associated with the problem of sound propagation in the outer chamber. On the other hand, the governing equation in the central duct has been solved in terms of the acoustic velocity potential considering the presence of a moving medium. The coupling between both regions and the corresponding acoustic fields has been carried out by means of a perforated duct and its acoustic impedance, adapted here to include absorbent material heterogeneities and mean flow effects simultaneously. It has been found that bulk density heterogeneities have a considerable influence on the silencer transmission loss.

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Section: Acoustic Model Of the Materials Heterogeneity Due To Densitymentioning

confidence: 99%

3D Acoustic Modelling of Dissipative Silencers with Nonhomogeneous Properties and Mean Flow

Sánchez-Orgaz

Denia

Martínez‐Casas

et al. 2014

Advances in Mechanical Engineering

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“…The attenuation computed by means of the mode matching approach for filling cases I and II is compared in Figs. 2 and 3 with experimental measurements [22,23] and numerical results. The former have been obtained in the experimental facilities of the research centre, and show good agreement with the TL obtained through the mode matching method, thus validating the proposed numerical technique from a practical point of view.…”

Section: Resultsmentioning

confidence: 91%

Numerical mode matching for sound propagation in silencers with granular material

Sánchez-Orgaz

Denia

Baeza

et al. 2019

Journal of Computational and Applied Mathematics

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This work presents an efficient numerical approach based on the combination of the mode matching technique and the finite element method (FEM) to model the sound propagation in silencers containing granular material and to evaluate their acoustic performance through the computation of transmission loss (TL). The methodology takes into account the presence of three-dimensional (3D) waves and the corresponding higher order modes, while reducing the computational expenditure of a full 3D FE calculation. First, the wavenumbers and transversal pressure modes associated with the silencer cross section are obtained by means of a two-dimensional FE eigenvalue problem, which allows the consideration of arbitrary transversal geometries and material heterogeneities. The numerical approach considers the possibility of using different filling levels of granular material, giving rise to cross sections with abrupt changes of properties located not only in the usual central perforated passage, but also in the transition between air and material, that involves a significant change in porosity. After solving the eigenvalue problem, the acoustic fields (acoustic pressure and axial velocity) are coupled at geometric discontinuities between ducts through the compatibility conditions to obtain the complete solution of the wave equation and the acoustic performance (TL). The granular material is analysed as a potential alternative to the traditional dissipative silencers incorporating fibrous absorbent materials.Sound propagation in granular materials can be modelled through acoustic equivalent properties, such as complex and frequency dependent density and speed of sound. TL results computed by means of the numerical approach proposed here show good agreement with full 3D FE calculations and experimental measurements. As expected, the numerical mode matching outperforms the computational expenditure of the full 3D FE approach. Different configurations have been studied to determine the influence on the TL of several parameters such as the size of the material grains, the filling level of the chamber, the granular material porosity and the geometry of the silencer cross section.

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“…This equivalent fluid has a complex effective density ρ m and a complex bulk modulus K m . The wavenumber k m and the characteristic impedance Z m of the equivalent fluid are also complex [10,57,134]. This model can be used for a number of fibrous materials used by industry in the manufacturing process of silencers [65,138,149,155,156,180].…”

Section: Materials Characterizationmentioning

confidence: 99%

Advanced numerical techniques for the acoustic modelling of materials and noise control devices in the exhaust system of internal combustion engines

Orgaz¹,

María²

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This Thesis is focused on the development and implementation of general and efficient numerical methods for the acoustic modelling and design of noise control devices in the exhaust system of combustion engines. Special attention is paid to silencers, that can be divided into reactive and dissipative configurations. For the latter, significant differences are likely to appear in their acoustic behaviour, depending on the temperature variations within the absorbent material. Also, material heterogeneities associated with uneven filling processes and time degradation due to the exhaust gases, can alter the silencer attenuation performance. Therefore, numerical techniques considering all these features are required to guarantee an accurate prediction of the acoustic behaviour.

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Acoustic response of fibrous absorbent materials to impulsive transient excitations

Cited by 5 publications

References 25 publications

3D Acoustic Modelling of Dissipative Silencers with Nonhomogeneous Properties and Mean Flow

3D Acoustic Modelling of Dissipative Silencers with Nonhomogeneous Properties and Mean Flow

Numerical mode matching for sound propagation in silencers with granular material

Advanced numerical techniques for the acoustic modelling of materials and noise control devices in the exhaust system of internal combustion engines

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