A point collocation approach to modelling large dissipative silencers

Kirby, Ray; Lawrie, Jane B.

doi:10.1016/j.jsv.2004.10.016

Cited by 83 publications

(56 citation statements)

References 16 publications

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“…To accommodate relatively large HVAC ducts, which are common in practice, a multi-modal sound field is chosen to excite the silencer. The effects of the splitter fairing are quantified by comparison with transmission loss predictions reported by Kirby and Lawrie [10] (who omit splitter end baffles), and with experimental results reported by Mechel [12]. The effects of varying both the porosity of the perforate, and the properties of the bulk reacting porous material, are also investigated.…”

Section: Introductionmentioning

confidence: 94%

“…On finding the duct/silencer eigenfunctions and associated wave numbers, the modal amplitudes may be computed by application of the axial matching conditions, after suitable truncation of each modal sum. A numerical approach similar to the one described by Kirby [13], and Kirby and Lawrie [10], is adopted here and so, after introducing the duct geometry and governing wave equations, a finite element eigenvalue analysis is described; this is followed by a point collocation scheme that seeks to fulfil the axial continuity conditions.…”

Section: Theorymentioning

confidence: 99%

“…The appropriate matching conditions (at 0 = x and L x = ) are continuity of acoustic pressure and normal particle velocity over the airway, and zero normal acoustic velocity over each splitter fairing. The most convenient approach to enforcing these matching conditions, and the one adopted by Kirby and Lawrie [10], is to choose an identical transverse finite element mesh in regions R 1 , R c and R 4 and to match over every common node. However, the addition of a perforate complicates matters, as additional nodes in the transverse finite element mesh are required at each perforate location in the silencer section.…”

Section: Numerical Matching Of Sound Fieldsmentioning

confidence: 99%

“…In fact, end effects for bulk reacting splitter silencers have only recently been quantified by Kirby and Lawrie [10], who demonstrated excellent agreement between numerical point collocation predictions and those found using an exact analytic approach. Kirby and Lawrie studied large HVAC silencers but the results were restricted to three splitters, and the effects of a perforate and splitter fairing were omitted.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Kirby

2005

The Journal of the Acoustical Society of America

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A numerical model based on the finite element method is developed for a finite length, HVAC splitter silencer. The model includes an arbitrary number of bulk-reacting splitters separated from the airway by a thin perforated metal sheet and accommodates higher order modes in the incident sound field. Each perforated sheet is joined to rigid, impervious, metallic fairing situated at either end of a splitter. The transmission loss for the silencer is quantified by application of the point collocation technique, and predictions are compared to experimental measurements reported in the literature. The splitter fairing is shown to significantly affect silencer performance, especially when higher order incident modes are present. It is concluded that laboratory measurements, and theoretical predictions, that are based on a predominantly plane wave sound source are unlikely to reflect accurately the true performance of an HVAC silencer in a real ducting system. 3

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Section: Introductionmentioning

confidence: 94%

Section: Theorymentioning

confidence: 99%

Section: Numerical Matching Of Sound Fieldsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Kirby

2005

The Journal of the Acoustical Society of America

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“…The equal modal energy density (EMED) assumption, i.e., F n j j 2 I n ¼ F m j j 2 I m for all m, n, has been chosen for the inlet as incident sound source, as it is a good representation of the sound field emanating from a fan in a ventilation system; see Kirby and Lawrie. 20 For EMED, the incoming modal amplitudes can be calculated from the formula…”

mentioning

confidence: 99%

Multiobjective muffler shape optimization with hybrid acoustics modeling

Airaksinen

Heikkola

2011

The Journal of the Acoustical Society of America

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This paper considers the combined use of a hybrid numerical method for the modeling of acoustic mufflers and a genetic algorithm for multiobjective optimization. The hybrid numerical method provides accurate modeling of sound propagation in uniform waveguides with non-uniform obstructions. It is based on coupling a wave based modal solution in the uniform sections of the waveguide to a finite element solution in the non-uniform component. Finite element method provides flexible modeling of complicated geometries, varying material parameters, and boundary conditions, while the wave based solution leads to accurate treatment of non-reflecting boundaries and straightforward computation of the transmission loss (TL) of the muffler. The goal of optimization is to maximize TL at multiple frequency ranges simultaneously by adjusting chosen shape parameters of the muffler. This task is formulated as a multiobjective optimization problem with the objectives depending on the solution of the simulation model. NSGA-II genetic algorithm is used for solving the multiobjective optimization problem. Genetic algorithms can be easily combined with different simulation methods, and they are not sensitive to the smoothness properties of the objective functions. Numerical experiments demonstrate the accuracy and feasibility of the model-based optimization method in muffler design.

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Acoustic radiation through a flexible shell in a bifurcated circular waveguide

Yaseen

Nawaz

2022

Math Methods in App Sciences

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The current study models and explains the fluid–structure coupled response of a flexible shell connected with two rigid coaxial shells via circular step discontinuities. Radiations from annular and inner regions of inlet rigid shells scatter on interfaces after interaction with the geometric variations and change of material properties. The flexible shell that supports vibrations along the shell is expressed though the Donnell–Mushtari formulation in the differential system. The mode‐matching technique is applied to solve the governing boundary value problem. The solution is projected on the orthogonal characteristics which in flexible casing is generalized as compared with the properties of acoustically rigid setting. The implication of generalized orthogonality relations governs additional constants that are found by defining the physical connection of shell with rigid disc. The clamped and pin‐jointed conditions are considered in this article. The scattering powers and transmission loss are analyzed against frequency, chamber length, and radii of shells for clamped and pin‐jointed edge conditions. It is found that the power propagation in annular shell and inner shell behave conversely. Moreover, configuration can be attenuated through the variation of dimensions of chamber and edge conditions.

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A point collocation approach to modelling large dissipative silencers

Cited by 83 publications

References 16 publications

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

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

Multiobjective muffler shape optimization with hybrid acoustics modeling

Acoustic radiation through a flexible shell in a bifurcated circular waveguide

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