Modelling of noise reduction in complex multistream jets

The paper presents a low-order prediction scheme for the noise change in multistream jets when the nozzle geometry is altered from a known baseline. The essence of the model is to predict the changes in acoustics due to the redistribution of the mean flow as computed by a Reynolds-averaged Navier–St...

Full description

Saved in:
Bibliographic Details
Published in:Journal of fluid mechanics 2018-01, Vol.834, p.555-599
Main Author: Papamoschou, Dimitri
Format: Article
Language:English
Subjects:
Acoustic noise
Acoustics
Aircraft
Computational fluid dynamics
Engines
Frameworks
Green's function
Green's functions
Jets
JFM Papers
Mathematical models
Modelling
Navier-Stokes equations
Noise
Noise prediction (aircraft)
Noise reduction
Nozzle geometry
Nozzles
Physics
Reynolds averaged Navier-Stokes method
Reynolds stress
Stress concentration
Stress distribution
Tertiary
Turbulence
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The paper presents a low-order prediction scheme for the noise change in multistream jets when the nozzle geometry is altered from a known baseline. The essence of the model is to predict the changes in acoustics due to the redistribution of the mean flow as computed by a Reynolds-averaged Navier–Stokes (RANS) solver. A RANS-based acoustic analogy framework is developed that addresses the noise in the polar direction of peak emission and uses the Reynolds stress as a time-averaged representation of the action of the coherent turbulent structures. The framework preserves the simplicity of the Lighthill acoustic analogy, using the free-space Green’s function, while accounting for azimuthal effects via special forms for the space–time correlation combined with source–observer relations based on the Reynolds stress distribution in the jet plume. Results are presented for three-stream jets with offset secondary and tertiary flows that reduce noise in specific azimuthal directions. The model reproduces well the experimental noise reduction trends. Principal mechanisms of noise reduction are elucidated.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2017.730