A finite element analysis of the convected acoustic wave motion in dissipative silencers

Peat, K.S.; Rathi, Keshav L.

doi:10.1006/jsvi.1995.0331

Cited by 85 publications

(72 citation statements)

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“…The benchmark predictions are chosen to be those provided by the finite element method described by Peat and Rathi [1] [12] is adequate only at very low frequencies, and the method is not sufficiently accurate to be used for studying larger dissipative silencers. Figures 7 and 8 successfully illustrate the motivation behind the new formulation since here it is obvious here that the method of Peat is unsuitable for silencers of a size commonly found in automobiles.…”

Section: Resultsmentioning

confidence: 99%

“…The advancement in design techniques has been accompanied by an increase in model complexity and the use of numerical formulations is now widespread. For example both the finite element method [1,2] and the boundary element method [3] have been used successfully to model dissipative silencers, although the finite element method is currently the most popular technique. Dissipative silencers of arbitrary shape, or even those with an arbitrary but uniform cross-section, require numerical techniques in order to obtain sufficiently accurate predictions [4].…”

Section: Introductionmentioning

confidence: 99%

“…Moreover the matching conditions at the silencer discontinuities are simplified by substituting series approximations for the Bessel and Neumann functions. The transmission loss predictions obtained are then compared against experimental measurement and also against predictions obtained by using the finite element method (see reference [1]). In order to provide a stringent test of the new method, larger silencers than those studied previously [11,12] are chosen here and two different porous materials are examined.…”

Section: Introductionmentioning

confidence: 99%

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Simplified Techniques for Predicting the Transmission Loss of a Circular Dissipative Silencer

Kirby

2001

Journal of Sound and Vibration

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A closed-form analytical solution for the transmission loss of a dissipative silencer with a circular cross-section is described. The silencer contains a bulk reacting acoustic absorbent which is separated from a mean gas flow by a perforated screen. Theoretical predictions of the silencer transmission loss for three different dissipative silencers are compared both with experimental data and with another more complex modelling technique. Good agreement is noted between the analytical theory and experimental data in the low-to-medium frequency range. Below a defined upper frequency limit the analytical technique is also shown to provide good agreement with the finite element method. In addition it is observed that, evenfor relatively high open area porosities, the perforate screen has a significant effect on dissipative silencer performance.3

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simplified Techniques for Predicting the Transmission Loss of a Circular Dissipative Silencer

Kirby

2001

Journal of Sound and Vibration

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“…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%

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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“…Sin duda, los elementos más importantes desde el punto de vista de atenuación acústica en la línea de escape son los silenciadores y su comportamiento ha recibido mucha atención [30,85,94,102,128]. Como mejora notable respecto a los modelos unidimensionales de silenciador iniciales [94], en losúltimos años se ha dedicado una intensa labor investigadora a su caracterización acústica tridimensional [30,128].…”

Section: Motivación Y Antecedentesunclassified

Contribución al modelado acústico de la línea de escape en motores de combustión. Aplicación a silenciadores y catalizadores

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Valencia, Junio de 2010 TESIS DOCTORALContribución al modelado acústico de la línea de escape en motores de combustión.Aplicación a silenciadores y catalizadores. Esta Tesis Doctoral ha sido posible gracias al apoyo del Ministerio de Ciencia e Innovación y la cofinanciación de FEDER (proyecto DPI2007-62635). ResumenEsta Tesis se centra en el desarrollo e implementación de métodos eficaces para el diseño y modelado acústico de la línea de escape de motores de combustión, y en concreto, de dos de sus componentes más relevantes desde el punto de vista de control de emisiones sonoras, como son los silenciadores y los catalizadores.Por ello, se realiza una revisión bibliográfica de los modelos unidimensionales y la representación matricial asociada. También se lleva a cabo una revisión de la literatura existente en cuanto a la caracterización de elementos perforados, materiales absorbentes y monolitos. Las limitaciones y deficiencias encontradas en los modelos de onda plana evidencian la necesidad de disponer de herramientas de modelado multidimensional, válidas a altas frecuencias y para geometrías de silenciadores y catalizadores sin dimensiones predominantes.Se aplica el método de elementos finitos a la resolución de la ecuación de ondas convectiva, mediante la formulación en presión, en el interior de silenciadores con material absorbente. Se estudia detalladamente el acoplamiento entre subdominios conectados mediante elementos perforados en el interior del silenciador. También se analiza el efecto del flujo medio en la impedancia acústica, prestando especial atención a las diferentes condiciones a satisfacer por el campo acústico. Por ello, se aplican las condiciones de continuidad de velocidad y desplazamiento y se comparan los resultados proporcionados por ambas con medidas experimentales.La capacidad que posee el método de elementos finitos para abordar geometrías arbitrarias es el motivo por el que también se aplica dicho método en el modelado acústico de catalizadores comerciales de automoción. Para el modelado acústico del catalizador se recurre a dos metodologías: (1) el modelo 3D conductos/3D monolito, utilizado en la bibliografía, en el que la aplicación del método de elementos finitos implica el cálculo del campo acústico tridimensional en el catalizador completo, y (2) el modelo 3D conductos/1D monolito, propuesto en la Tesis, en el que se sustituye el monolito por una matriz de transferencia que asume una propagación unidimensional en su interior. Se comparan los resultados obtenidos mediante ambas metodologías con medidas experimentales, mostrando que la técnica propuesta da lugar a predicciones más ajustadas a la experimentación. Posteriormente, se extiende el modelo 3D conductos/1D monolito para incluir catalizadores con presencia de flujo medio en los i ii capilares.En respuesta al alto coste computacional asociado al método de elementos finitos se desarrollan herramientas analíticas tridimensionales de modelado mediante el método de ajuste modal. El desarrollo de dichas herramientas se basa en e...

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A finite element analysis of the convected acoustic wave motion in dissipative silencers

Cited by 85 publications

References 0 publications

Simplified Techniques for Predicting the Transmission Loss of a Circular Dissipative Silencer

Simplified Techniques for Predicting the Transmission Loss of a Circular Dissipative Silencer

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

Contribución al modelado acústico de la línea de escape en motores de combustión. Aplicación a silenciadores y catalizadores

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