Research Papers

Predictive Large Eddy Simulation for Jet Aeroacoustics–Current Approach and Industrial Application

[+] Author and Article Information
James Tyacke

Department of Engineering,
University of Cambridge,
Cambridge CB2 1PZ, UK
e-mail: jct53@cam.ac.uk

Iftekhar Naqavi, Zhong-Nan Wang, Paul Tucker

Department of Engineering,
University of Cambridge,
Cambridge CB2 1PZ, UK

Peer Boehning

System Design, Aeroacoustics
Rolls-Royce Deutschland
Dahlewitz, Germany

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 9, 2016; final manuscript received December 16, 2016; published online March 15, 2017. Assoc. Editor: Rakesh Srivastava.

J. Turbomach 139(8), 081003 (Mar 15, 2017) (13 pages) Paper No: TURBO-16-1234; doi: 10.1115/1.4035662 History: Received September 09, 2016; Revised December 16, 2016

The major techniques for measuring jet noise have significant drawbacks, especially when including engine installation effects such as jet–flap interaction noise. Numerical methods including low order correlations and Reynolds-averaged Navier–Stokes (RANS) are known to be deficient for complex configurations and even simple jet flows. Using high fidelity numerical methods such as large eddy simulation (LES) allows conditions to be carefully controlled and quantified. LES methods are more practical and affordable than experimental campaigns. The potential to use LES methods to predict noise, identify noise risks, and thus modify designs before an engine or aircraft is built is a possibility in the near future. This is particularly true for applications at lower Reynolds numbers such as jet noise of business jets and jet-flap interaction noise for under-wing engine installations. Hence, we introduce our current approaches to predicting jet noise reliably and contrast the cost of RANS–numerical-LES (RANS–NLES) with traditional methods. Our own predictions and existing literature are used to provide a current guide, encompassing numerical aspects, meshing, and acoustics processing. Other approaches are also briefly considered. We also tackle the crucial issues of how codes can be validated and verified for acoustics and how LES-based methods can be introduced into industry. We consider that hybrid RANS–(N)LES is now of use to industry and contrast costs, indicating the clear advantages of eddy resolving methods.

Copyright © 2017 by ASME
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Fig. 1

Definition of certification points for the noise measurement: approach, fly-over, and sideline

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Fig. 2

Open jet facility to measure jet noise with a flight stream

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Fig. 3

Flow features and turbulence modeling approach

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Fig. 4

Validation of the KEP scheme on the canonical flow cases: (a) Tollmien–Schlichting wave and (b) homogeneous isotropic decaying turbulence

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Fig. 5

The axial velocity field of a subsonic jet simulated by KEP scheme and Roe scheme: (a) KEP scheme and (b) Roe scheme

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Fig. 6

Axial velocity and turbulence intensity along the centerline and nozzle lipline: (a) axial velocity and (b) turbulence intensity

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Fig. 7

Numerical boundary treatment illustration

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Fig. 8

Typical round nozzle mesh topology

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Fig. 9

Comparison of current axial and radial mesh spacings with other literature, i.e., number of spacings per notional jet diameter along SLo: (a) axial and (b) radial

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Fig. 10

Structured and hybrid axial mesh planes showing azimuthal mesh structure: (a) structured and (b) hybrid

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Fig. 11

Hybrid structured–unstructured mesh for (a), an isolated nozzle with the inset showing the structured-unstructured interface and (b), an initial installed round coaxial nozzle with an inset showing regions of different axial resolution

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Fig. 12

RANS–NLES of an installed engine with internal geometry modeling

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Fig. 13

(a) Unstructured hexahedral Octree mesh of an installed nozzle and (b) axial velocity contours at x/D = 3 (1D downstream of the wing trailing edge)

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Fig. 14

Localized unstructured meshing of a chevron nozzle: (a) topology and (b) example initial mesh cut-plane

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Fig. 15

Multiple FW-H surfaces with upstream and multiple downstream closing disks

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Fig. 16

OASPL and SPL spectra for the hot, cold and cold jet with flight stream without closing disks: (a) hot jet, (b) cold jet, (c) cold jet with flight stream, (d) hot jet, (e) cold jet, and (f) cold jet with flight stream

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Fig. 17

OASPL and SPL spectra for the hot, cold, and cold jet with flight stream with closing disks: (a) hot jet, (b) cold jet, (c) cold jet with flight stream, (d) hot jet, (e) cold jet, and (f) cold jet with flight stream

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Fig. 18

Example expert system-based process for LES of complex jet aeroacoustics




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