Computation of Spinning Modal Radiation from an Unflanged Duct

Zhang, Xin; Chen, Xiaoming; Morfey, C. L.; Nelson, Philip A.

doi:10.2514/6.2002-2475

Cited by 18 publications

(33 citation statements)

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“…To accurately and efficiently predict sound radiation out of a duct with flow, a CAA method based on the LEE model was presented in our previous work [7,[9][10][11][12]. A 2.5-D LEE model was developed to solve sound radiation out of an axisymmetric duct on a 2-D computational domain [9,10].…”

Section: = @Wmentioning

confidence: 99%

“…A 2.5-D LEE model was developed to solve sound radiation out of an axisymmetric duct on a 2-D computational domain [9,10]. The incoming spinning modes were realized through an absorbing nonreflecting boundary treatment, which admits incoming waves and damps spurious waves generated by the numerical methods [11].…”

Section: = @Wmentioning

confidence: 99%

“…(2), the general 3-D LEE in cylindrical coordinates could be simplified to a set of 2-D equations, which are generally termed 2.5-D LEE equations [9]. The complete governing equations for a single frequency k and a single circumferential mode m are …”

Section: A Propagation: Linearized Euler Equationsmentioning

confidence: 99%

“…The spinning modes are introduced in the computation domain as boundary conditions. More details about the implementations and applications of 2.5-D LEE can be found in the literature [7,9,10,12].…”

Section: A Propagation: Linearized Euler Equationsmentioning

confidence: 99%

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Efficient Computation of Spinning Modal Radiation Through an Engine Bypass Duct

Huang

Chen

et al. 2008

AIAA Journal

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The aim of this work is to accurately and efficiently predict sound radiation out of a duct with flow. The sound propagation inside a generic engine bypass duct, refractions by the shear layer of the exhaust flow, and propagation in the near field are the main focus of the study. The prediction uses either a modified form of linearized Euler equations or an alternative model based on acoustic perturbation equations, which were extended to cylindrical coordinates. The two models were compared on a canonical case of sound propagation out of a semi-infinite duct with flow. Good agreements between the predictions were achieved. The more general case of a generic aircraft engine bypass duct with flow was then investigated with the technique of adaptive mesh refinement to increase the computational efficiency. The results show that both linearized Euler equations and acoustic perturbation equations models can predict the near-field sound propagation and far-field directivity. The acoustic perturbation equations model, however, is more adaptive for its suitability to an arbitrary background mean flow.

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Section: = @Wmentioning

confidence: 99%

Section: = @Wmentioning

confidence: 99%

Section: A Propagation: Linearized Euler Equationsmentioning

confidence: 99%

Section: A Propagation: Linearized Euler Equationsmentioning

confidence: 99%

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Efficient Computation of Spinning Modal Radiation Through an Engine Bypass Duct

Huang

Chen

et al. 2008

AIAA Journal

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“…4 For many engine-aircraft engineering applications this problem has served as an important first model, useful for understanding the physics and for validating and benchmarking numerical solutions. [4][5][6] Exactly for this reason Munt's solution was recently generalized by Gabard e.a. 7,8 to include a doubly infinite hard-walled centerbody or hub.…”

Section: Introductionmentioning

confidence: 99%

Sound Radiation from an Annular Duct with Jet Flow and a Lined Center Body

Demír

Rienstra

2006

12th AIAA/CEAS Aeroacoustics Conference (27th AIAA Aeroacoustics Conference)

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Analytical solutions for the problem of radiation of sound from a duct with flow have been shown to serve as an important first model for acoustic engine-aircraft engineering applications, useful for understanding the physics and for validating and benchmarking numerical solutions.The probably most important steps were taken by Levine & Schwinger and Munt. He showed that application of the Kutta condition, in order to determine the amount of vorticity shed from the trailing edge, goes together with excitation of the Kelvin-Helmholtz instability wave of the jet.In the present work we will extend this work further by considering the effect of lining on the centerbody and on the afterbody, which is mathematically a much different problem. The lining is of impedance type, while the Ingard-Myers boundary condition is taken to include the effect of the mean flow. The flow is assumed to be subsonic. Differences in the (otherwise uniform) mean flow velocity, density and temperature are taken into account. A vortex sheet which separates the jet from the outer flow emanates from the edge. Due to this velocity discontinuity of the mean flow the jet is unstable. An analytical solution satisfying the full or partial Kutta condition at the trailing edge is found by means of the Wiener-Hopf technique. The jet instability wave is taken apart from the rest of the solution and the effect of applying the Kutta condition to the scattered field is shown, both in far field and near field. The influence of lining on the radiation is displayed graphically.The problem of a lined afterbody is of particular interest, because its Wiener-Hopf solution embodies a novel application of the so-called "weak factorization".It should be noted that our primary goal here is to archive the mathematical solution, rather than to unravel all physical possibilities and explore the whole spectrum of problem parameters and their combinations.

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The non‐reflective interface: an innovative forcing technique for computational acoustic hybrid methods

Redonnet

Lockard

Khorrami

et al. 2015

Numerical Methods in Fluids

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Summary The present article concerns a commonly used methodology for the numerical simulation of acoustic emission and propagation phenomena. We consider the so‐called multi‐stage hybrid acoustic approach, in which a given noise problem is simulated via a sequence of weakly coupled computations of noise generation and acoustic propagation stages, wherein the simulation of the propagation stage is based on advanced Computational AeroAcoustics (CAA) techniques. The paper introduces an original forcing technique, namely, the Non‐Reflective Interface (NRI), to enable the transfer of an acoustic signal from an a priori noise generation stage into a CAA‐based acoustic propagation phase. Unlike most existing forcing techniques, the NRI is non‐reflective (or anechoic) in nature and, therefore, can properly handle the backscattering effects arising during the noise propagation stage. This attribute makes the NRI‐based weak‐coupling procedure and the associated CAA‐based hybrid approach compatible with a larger variety of realistic noise problems (such as those involving installed configurations in wind tunnel experiments, for instance). The NRI technique is first validated via several test cases of increasing complexity and is then applied to two aerodynamic noise problems. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

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Computation of Spinning Modal Radiation from an Unflanged Duct

Cited by 18 publications

References 0 publications

Efficient Computation of Spinning Modal Radiation Through an Engine Bypass Duct

Efficient Computation of Spinning Modal Radiation Through an Engine Bypass Duct

Sound Radiation from an Annular Duct with Jet Flow and a Lined Center Body

The non‐reflective interface: an innovative forcing technique for computational acoustic hybrid methods

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