An iterative finite element-integral technique for predicting sound radiation from turbofan inlets in steady flight

Horowitz, S. J.; Sigman, R. K.; Zinn, B. T.

doi:10.2514/6.1982-124

Cited by 13 publications

(3 citation statements)

References 8 publications

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“…It is less well suited to flow acoustics since an analytic Green's function is required and this is available only for uniform flow. The BEM was used in early computational models for turbofan acoustics by coupling it iteratively to finite elements in the near field [48]. More recently Dunn, et al [49] presented a Boundary Integral approach to modelling propagation and radiation of forward and rear arc noise from a thin walled, lined cylindrical duct with uniform flow and a turbofan-like source.…”

Section: Boundary Element Methodsmentioning

confidence: 99%

Numerical methods for noise propagation in moving flows, with application to turbofan engines

Astley

2009

Acoust. Sci. & Tech.

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This article reviews the development and application of Computational AeroAcoustics (CAA) to acoustic propagation on subsonic mean flows, with a particular focus on methods used to predict acoustic radiation from turbofan aeroengines. The governing equations are presented and particular issues such as the formulation of impedance and far field boundary conditions, the treament of Kelvin-Helmholtz instabilities, resolution requirements and methods for controlling dispersion error, are discussed. The status of current CAA methods is reviewed. Finally, the matter of validation against benchmark problems and measured data is explored.

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Section: Boundary Element Methodsmentioning

confidence: 99%

Numerical methods for noise propagation in moving flows, with application to turbofan engines

Astley

2009

Acoust. Sci. & Tech.

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“…Numerical Model . A hybrid numerical program has been developed (72) and exercised (73) to calculate both the internal and external sound propagation for actual engine inlet geometry and flow conditions. It is a hybrid program in the sense that a finite element method is used within the duct and in the near field and an integral radiation method handles the far field.…”

Section: Inlet Radiationmentioning

confidence: 99%

Aircraft Turbofan Noise

Groeneweg

Rice

1983

Volume 5: Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; Process Industries

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Recent advances in the understanding of turbofan noise generation and suppression in aircraft engines are reviewed with particular emphasis on NASA research. The review addresses each link in the chain of physical processes which connect unsteady flow interactions with fan blades to far field noise. Mechanism identification and description, duct propagation, radiation and acoustic suppression are discussed. Recent advances in the experimental technique of fan inflow control assure that in-flight generation mechanisms are not ma.,ked by extraneous sources in static tests. Rotor blade surface pressure and wake velocity measurements aid the determination of the types and strengths of the generation mechanisms. Approaches to predicting or measuring acoustic mode content, optimizing treatment impedance to maximize attenuation, translating impedance into porous wall structure and interpreting far field directivity patterns are illustrated by comparisons of analytical and experimental results. A persistent theme of the review is the interdependence of source and acoustic treatment design to minimize far field noise. Areas requiring further research are discussed and the relevance of aircraft turbofan results to quieting other turbomachinery installations is addressed.

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“…Modeling acoustic propagation in an unbounded domain requires the use of specific methods, such as boundary integral methods [2,3], infinite elements [4][5][6], absorbing layers [7,8], or nonreflecting boundary condition (NRBC) which may be local [9,10] or non-local [11][12][13][14][15]. Among infinite domain problems, a distinction must be made between scattering problems around a body in a free space and problems in semi-infinite or infinite waveguides that make up the issue of the present work.…”

Section: Introductionmentioning

confidence: 99%

Non‐reflecting boundary conditions for acoustic propagation in ducts with acoustic treatment and mean flow

Redon

Dhia

Mercier

et al. 2011

Numerical Meth Engineering

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International audienceWe consider a time-harmonic acoustic scattering problem in a 2D infinite waveguide with walls covered with an absorbing material, in the presence of a mean flow assumed uniform far from the source. To make this problem suitable for a finite element analysis, the infinite domain is truncated. This paper concerns the derivation of a non-reflecting boundary condition on the artificial boundary by means of a Dirichlet-to-Neumann (DtN) map based on a modal decomposition. Compared with the hard-walled guide case, several difficulties are raised by the presence of both the liner and the mean flow. In particular, acoustic modes are no longer orthogonal and behave asymptotically like the modes of a soft-walled guide. However, an accurate approximation of the DtN map can be derived using some bi-orthogonality relations, valid asymptotically for high-order modes. Numerical validations show the efficiency of the method. The influence of the liner with or without mean flow is illustrated

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An iterative finite element-integral technique for predicting sound radiation from turbofan inlets in steady flight

Cited by 13 publications

References 8 publications

Numerical methods for noise propagation in moving flows, with application to turbofan engines

Numerical methods for noise propagation in moving flows, with application to turbofan engines

Aircraft Turbofan Noise

Non‐reflecting boundary conditions for acoustic propagation in ducts with acoustic treatment and mean flow

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