The acoustic characteristics of duct bends

Cabelli, A.

doi:10.1016/0022-460x(80)90393-4

Cited by 27 publications

(11 citation statements)

References 7 publications

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“…In this section we show an example of applications of the MMM for the characterization of a particular bend, which has been already characterized by an experiment and a finite differences method calculation in the literature. 8 The geometry consists in a bend joining two semiinfinite straight ducts, as shown in Fig. 1, with f ϭ2.62 and h/R 1 ϭ8.…”

Section: Applicationmentioning

confidence: 99%

“…The algebraic method presented in Appendix D gives similar results to our method, as expected. Experimental and numerical results of Cabelli 8 for the same geometry are also reported. The multimodal method gives results in good agreement with the experimental measurements.…”

Section: Applicationmentioning

confidence: 99%

“…Methods different from the BMM have been used, such as the Galerkin method ͑Tam 7 ͒, finite differences method ͑Cabelli 8 ͒ or more recently a method based on parabolic approximation ͑Dougherty 9 ͒. Such approaches permit to investigate more general cases than those, restricted, presented previously, and are powerful to yield information.…”

Section: Introductionmentioning

confidence: 99%

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Sound propagation in rigid bends: A multimodal approach

Félix

Pagneux

2001

The Journal of the Acoustical Society of America

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The sound propagation in a waveguide with bend of finite constant curvature is analyzed using multimodal decomposition. Two infinite first-order differential equations are constructed for the pressure and velocity in the bend, projected on the local transverse modes. A Riccati equation for the impedance matrix is then derived, which can be numerically integrated after truncation at a sufficient number of modes. An example of validation is considered and results show the accuracy of the method and its suitability for the formulation of radiation conditions. Reflection and transmission coefficients are also computed, showing the importance of higher order mode generation at the junction between the bend and the straight ducts. The case of varying cross-section curved ducts is also considered using multimodal decomposition.

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Section: Applicationmentioning

confidence: 99%

Section: Applicationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sound propagation in rigid bends: A multimodal approach

Félix

Pagneux

2001

The Journal of the Acoustical Society of America

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“…Low frequencies have a much lower dependence on amplitude than higher frequencies and larger amplitudes have a much more sensitive dependence on frequency, with interesting new resonances arising. Also plotted are the experimental results of Cabelli (1980). Nonlinearity may account for the discrepancy between the experimental results and the linear multimodal method, though as no amplitude was stated one cannot be certain.…”

Section: Nonlinear Reflectionmentioning

confidence: 99%

“…Ting & Miksis 1983) which limit the applicability of the solution to, for example, slender ducts; direct computation (e.g. Cabelli 1980) limiting the physical insight; and methods based on the separation of variables. One such method, the multimodal method (MMM) – first proposed by Pagneux, Amir & Kergomard (1996) for the study of ducts of varying cross-section and subsequently generalised to two-dimensional (2-D) curved ducts (Félix & Pagneux 2001), three-dimensional (3-D) curved ducts (Félix & Pagneux 2002) and lined ducts (Bi et al.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear sound propagation in two-dimensional curved ducts: a multimodal approach

McTavish

2019

J. Fluid Mech.

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A method for studying weakly nonlinear acoustic propagation in two-dimensional ducts of general shape – including curvature and variable width – is presented. The method is based on a local modal decomposition of the pressure and velocity in the duct. A pair of nonlinear ordinary differential equations for the modal amplitudes of the pressure and velocity modes is derived. To overcome the inherent instability of these equations, a nonlinear admittance relation between the pressure and velocity modes is presented, introducing a novel ‘nonlinear admittance’ term. Appropriate equations for the admittance are derived which are to be solved through the duct, with a radiation condition applied at the duct exit. The pressure and velocity are subsequently found by integrating an equation involving the admittance through the duct. The method is compared, both analytically and numerically, against published results and the importance of nonlinearity is demonstrated in ducts of complex geometry. Comparisons between ducts of differing geometry are also performed to illustrate the effect of geometry on nonlinear sound propagation. A new ‘nonlinear reflectance’ term is introduced, providing a more complete description of acoustic reflection that also takes into account the amplitude of the incident wave.

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Narrowband Noise Attenuation Characteristics of in-Duct Acoustic Screens

Rim

Kim

2000

Journal of Sound and Vibration

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The acoustic characteristics of duct bends

Cited by 27 publications

References 7 publications

Sound propagation in rigid bends: A multimodal approach

Sound propagation in rigid bends: A multimodal approach

Nonlinear sound propagation in two-dimensional curved ducts: a multimodal approach

Narrowband Noise Attenuation Characteristics of in-Duct Acoustic Screens

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