Modal conversion from untreated to treated cylindrical ducts

Montetagaud, Fabienne; Batard, Hervé; Lempereur, P.; Legros, C.

doi:10.2514/6.1998-2309

Cited by 2 publications

(1 citation statement)

References 5 publications

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“…Eversman and Cook 4 changed the eigenvalue equation into a differential one which can be integrated by using the Runge-Kutta algorithm. Montetagaud et al 5 used this method with a more precise step. Rienstra 6 identified the modes in ducts in two categories: The duct modes resulting from the finiteness of the duct geometry, and the surface waves that exist only near the wall surface in a way essentially independent of the rest of the duct.…”

Section: Introductionmentioning

confidence: 98%

Calculations of modes in circumferentially nonuniform lined ducts

2008

The Journal of the Acoustical Society of America

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This paper proposes a computationally efficient method of determining eigenfunctions and eigenvalues of acoustic modes propagating in circular lined ducts with zero or uniform flow. Linings with circumferentially nonuniform impedance, as found in nacelle acoustics, are the focus. The method of solution adapts in two important respects--the presence of flow and the imposition of impedance boundary conditions--the series expansion method first proposed by Pagneux et al. [J. Acoust. Soc. Am. 110, 1307-1314 (2001)] to calculate the eigenvalues of Lamb modes. The inclusion of flow, and a corresponding different method of solution leading to an improved convergence of eigenvalues (O(N(-5)), N is the truncation of radial basis of expansion), is the important new feature as compared to the previous adaptation by Bi et al. [J. Acoust. Soc. Am. 122, 280-291 (2007)]. As a result, it becomes possible to safely determine and in a simple manner the eigenvalues and eigenfunctions of circumferentially nonuniform lined ducts in the presence of uniform flow, up to relatively high frequencies (e.g., 30

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Section: Introductionmentioning

confidence: 98%