The influence of baffle fairings on the acoustic performance of rectangular splitter silencers

Kirby, Ray

doi:10.1121/1.2010267

Cited by 40 publications

(28 citation statements)

References 17 publications

(36 reference statements)

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“…This agreement between prediction and measurement for a silencer with parallel baffles represents an improvement on that seen previously in the literature. 3,20 However, it is noted that this silencer has a relatively high open area of D ¼ 50%, whereas those problems found by Kirby 3 and Mechel 20 generally occurred for lower percentage open areas. Moreover, a further comparison between prediction and experiment for silencers not shown here reveals that for percentage open areas below about 35% some over prediction is to be expected at higher frequencies.…”

Section: Resultsmentioning

confidence: 93%

“…This type of over prediction has been observed before for SDM silencers with low percentage open areas. 3,20 It is not entirely clear why this discrepancy exists, although it has been speculated previously 3 that this may be caused by sound traveling down the walls of the silencer during experimental measurements. However, the experimental apparatus was designed specifically to try and minimize this effect and tests were undertaken to confirm that the limiting value for the IL of the test rig was significantly above those values for IL reported here.…”

Section: Resultsmentioning

confidence: 94%

“…This is because in the silencer section additional nodes appear on either side of the perforate. 3 Thus, Eqs. (13)-(20) deliver 2ðn A þ n M þn 1 Þ collocation points, with 2ðm 1 þ m s Þ unknown modal amplitudes.…”

Section: Theorymentioning

confidence: 97%

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A three dimensional investigation into the acoustic performance of dissipative splitter silencers

Kirby

Williams

Hill³

2014

The Journal of the Acoustical Society of America

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Splitter silencers are found in ventilation and gas turbine systems and consist of parallel baffles of porous material placed within a duct so that they split the mean gas flow. Theoretical investigations into dissipative splitter silencers have generally been limited to two dimensions and this limits the analysis to finding the silencer eigenmodes or, for a finite length silencer, to rectangular baffles only. In this article a numerical point collocation approach is used to extend theoretical predictions to three dimensions. This facilitates the analysis of more complex silencer designs such as "bar" silencers and theoretical predictions are validated by comparison with experimental measurements. The insertion loss of different silencer designs is evaluated and the performance of a bar silencer is compared to traditional designs for rectangular and circular ducts. It is shown that a bar silencer with a volume of material identical to an equivalent parallel baffle design delivers a significant improvement in insertion loss at higher frequencies, although this is at the expense of a small reduction in performance at low frequencies. It is also shown that under most circumstances it is possible to get good agreement between prediction and experiment even for relatively large Helmholtz numbers.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 94%

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A three dimensional investigation into the acoustic performance of dissipative splitter silencers

Kirby

Williams

Hill³

2014

The Journal of the Acoustical Society of America

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“…This method relies on solving the appropriate eigenproblem over the cross-section of the duct. [1][2][3][4][5][6][7] Eigenfunctions can be solved either analytically, 5 using a root finding algorithm, 3,6 or by discretization techniques using trigonometric function decomposition, 1,2 the finite element method, 4 or layered discretizations. 7 It is also possible to perform three-dimensional finite element analysis.…”

Section: Introductionmentioning

confidence: 99%

A homogenization method used to predict the performance of silencers containing parallel splitters

Nennig

Binois

Perrey‐Debain

et al. 2015

The Journal of the Acoustical Society of America

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An analytical model based on a homogenization process is used to predict and understand the behavior of finite length splitter/baffle-type silencers inserted axially into a rigid rectangular duct. Such silencers consist of a succession of parallel baffles made of porous material and airways inserted axially into a rigid duct. The pore network of the porous material in the baffle and the larger pores due to the airway can be considered as a double porosity (DP) medium with well-separated pore sizes. This scale separation leads by homogenization to the DP model, widely used in the porous material community. This alternative approach based on a homogenization process sheds physical insight into the attenuation mechanisms taking place in the silencer. Numerical comparisons with a reference method are used to show that the theory provides good results as long as the pressure wave in the silencer airways propagates as a plane wave parallel to the duct axis. The explicit expression of the axial wavenumber in the DP medium is used to derive an explicit expression for the optimal resistivity value of the porous material, ensuring the best dissipation for a given silencer geometry.

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“…A similar expression holds for the guide 2, with a sign − before v 0 . When the determinants are unity, the eigenvectors are given by Equation (18).…”

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confidence: 99%

Propagation of Acoustic Waves in Two Waveguides Coupled by Perforations. II. Analysis of Periodic Lattices of Finite Length

Pachebat¹,

Kergomard²

2016

Acta Acustica united with Acustica

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The paper deals with the generic problem of two waveguides coupled by perforations, which can be perforated tube mufflers without or with partitions, possibly with absorbing materials. Other examples are ducts with branched resonators of honeycomb cavities, which can be coupled or not, and splitter silencers. Assuming low frequencies, only one mode is considered in each guide. The propagation in the two waveguides can be very different, thanks e.g. to the presence of constrictions. The model is a discrete, periodic one, based upon 4th-order impedance matrices and their diagonalization. All the calculation is analytical, thanks to the partition of the matrices in 2nd-order matrices, and allows the treatment of a very wide types of problems. Several aspects are investigated: the local or non-local character of the reaction of one guide to the other; the definition of a coupling coefficient; the effect of finite size when a lattice with n cells in inserted into an infinite guide; the relationship between the Insertion Loss and the dispersion. The assumptions are as follows: linear acoustics, no mean flow, rigid wall. However the effect of the series impedance of the perforations, which is generally ignored, is taken into account, and is discussed. When there are no losses, it is shown that, for symmetry reasons, the cutoff frequencies depend on either the series impedance or the shunt admittance, and are the eigenfrequencies of the cells of the lattice, with zero-pressure or zero-velocity at the ends of the cells.

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The influence of baffle fairings on the acoustic performance of rectangular splitter silencers

Cited by 40 publications

References 17 publications

A three dimensional investigation into the acoustic performance of dissipative splitter silencers

A three dimensional investigation into the acoustic performance of dissipative splitter silencers

A homogenization method used to predict the performance of silencers containing parallel splitters

Propagation of Acoustic Waves in Two Waveguides Coupled by Perforations. II. Analysis of Periodic Lattices of Finite Length

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