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

Sánchez-Orgaz, E.M.; Denia, F.D.; Martínez‐Casas, José; Baeza, Luis

doi:10.1155/2014/537935

Cited by 10 publications

(24 citation statements)

References 22 publications

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“…The relation between the acoustic pressure and the potential is given by [25] D Φ a a t a P ρ = − (4) Similarly to earlier studies [33][34][35], the mean flow is assumed unidirectional, with Umf ≠ 0, Vmf = Wmf = 0, and transversely uniform over the duct cross-section. Therefore, no dependence exists on the (y, z) coordinates.…”

Section: Wave Propagation In the Central Passagementioning

confidence: 99%

“…[4] due to the spatial variation of the air properties. For a given temperature distribution, mass conservation is considered to compute the axial variation of Umf [10,12] for a prescribed inlet mean flow Mach number Mi.…”

Section: Wave Propagation In the Central Passagementioning

confidence: 99%

“…In the absence of mean flow, the wave propagation in the heterogeneous absorbent material is governed by [3,4,25,26,37]…”

Section: Wave Propagation In the Outer Chambermentioning

confidence: 99%

“…These spatial variations can arise, for example, from uneven filling processes [1][2][3][4], non-uniform mean flow fields [5] and thermal gradients [6,7]. In the latter case, the difficulties associated with experimental measurements at high temperatures make it necessary to find computational approaches useful to evaluate the acoustic behaviour of the silencer.…”

Section: Introductionmentioning

confidence: 99%

“…[7], where a numerical approach based on the finite element method (FEM) was presented to analyze the effect of a continuously varying temperature field on the transmission loss of perforated dissipative silencers. A suitable version of the wave equation was required to account for heterogeneous density and speed of sound [3,4,25,26]. In the previous approaches [6,7,31], the effect of the temperature on the acoustic properties of the absorbent material were accounted for by modifying the steady air-flow resistivity in the initial model of the material obtained at room temperature.…”

Section: Introductionmentioning

confidence: 99%

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Finite element based acoustic analysis of dissipative silencers with high temperature and thermal-induced heterogeneity

Denia

Sánchez-Orgaz

Martínez‐Casas

et al. 2015

Finite Elements in Analysis and Design

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A mixed finite element model has been derived for the acoustic analysis of perforated dissipative silencers including several effects simultaneously: (1) High temperature and thermal gradients in the central duct and the outer absorbent material; (2) A perforated passage carrying non-uniform axial mean flow. For such a combination, the properties of sound propagation media and flow are inhomogeneous and vary with position. The material of the outer chamber can be modelled by its complex equivalent acoustic properties, which completely determine the propagation of sound waves in the air contained in the absorbent medium. Temperature gradients introduce variations in these properties that can be evaluated through a heterogeneous temperature-dependent resistivity in combination with material models obtained at room temperature. A pressure-based wave equation for stationary medium is then used with the equivalent density and speed of sound of the absorbent material varying as functions of the spatial coordinates. Regarding the central air passage, a wave equation in terms of acoustic velocity potential can be used to model the non-uniform moving medium since the presence of temperature variations introduce not only heterogeneous acoustic properties of the air but also a gradient in the mean flow velocity. The acoustic connection between the central passage and the outer chamber is given by the acoustic impedance of the perforated duct. This impedance depends on the heterogeneous properties of the absorbent material and the non-uniform mean flow, leading to a spatial variation of the acoustic coupling and also to additional convective terms in the governing equations. The results presented show the influence of temperature, thermal gradients and mean flow on the transmission loss of automotive silencers. It has been found that high temperature and thermal-induced heterogeneity can have a significant influence on the acoustic attenuation of an automotive silencer and so should be included in theoretical models. In some particular configurations it may be relatively accurate to approximate the temperature field by using a uniform profile with an average value, specially for low resistivity materials. It has been shown, however, that this is not always possible and attenuation overestimation is likely to be predicted, mainly for high radial thermal gradients and high material flow resistivities, if the temperature distribution is not taken into account.

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Section: Wave Propagation In the Central Passagementioning

confidence: 99%

Section: Wave Propagation In the Central Passagementioning

confidence: 99%

“…In the absence of mean flow, the wave propagation in the heterogeneous absorbent material is governed by [3,4,25,26,37]…”

Section: Wave Propagation In the Outer Chambermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Finite element based acoustic analysis of dissipative silencers with high temperature and thermal-induced heterogeneity

Denia

Sánchez-Orgaz

Martínez‐Casas

et al. 2015

Finite Elements in Analysis and Design

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Acoustic attenuation and effective properties of single and periodic Helmholtz resonators having porous core

Dandsena

Jena

2023

Applied Acoustics

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Point collocation scheme in silencers with temperature gradient and mean flow

Denia

Sánchez-Orgaz

Baeza

et al. 2016

Journal of Computational and Applied Mathematics

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This work presents a mathematical approach based on the point collocation technique to compute the transmission loss of perforated dissipative silencers with transversal temperature gradients and mean flow. Three-dimensional wave propagation is considered in silencer geometries with arbitrary, but axially uniform, cross section. To reduce the computational requirements of a full multidimensional finite element calculation, a method is developed combining axial and transversal solutions of the wave equation. First, the finite element method is employed in a two-dimensional problem to extract the eigenvalues and associated eigenvectors for the silencer cross section. Mean flow as well as transversal temperature gradients and the corresponding thermal-induced material heterogeneities are included in the model. In addition, an axially uniform temperature field is taken into account, its value being the inlet/outlet average. A point collocation technique is then used to match the acoustic fields (pressure and axial acoustic velocity) at the geometric discontinuities between the silencer chamber and the inlet and outlet pipes. Transmission loss predictions are compared favorably with a general three-dimensional finite element approach, offering a reduction in the computational effort.

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

Cited by 10 publications

References 22 publications

Finite element based acoustic analysis of dissipative silencers with high temperature and thermal-induced heterogeneity

Finite element based acoustic analysis of dissipative silencers with high temperature and thermal-induced heterogeneity

Acoustic attenuation and effective properties of single and periodic Helmholtz resonators having porous core

Point collocation scheme in silencers with temperature gradient and mean flow

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