Imperial College London
Professor Xuesong Wu

ProfessorXuesongWu

Faculty of Natural Sciences, Department of Mathematics

Professor of Applied Mathematics
 
 
 
//

Contact

 

+44 (0)20 7594 8494x.wu Website

 
 
//

Location

 

738Huxley BuildingSouth Kensington Campus

//

Summary

 

Publications

Citation

BibTex format

@article{Wu:2019:10.1098/rsta.2019.0077,
author = {Wu, X and Zhang, Z},
doi = {10.1098/rsta.2019.0077},
journal = {Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences},
pages = {1--18},
title = {First-principle description of acoustic radiation of shear flows},
url = {http://dx.doi.org/10.1098/rsta.2019.0077},
volume = {377},
year = {2019}
}
Download

RIS format (EndNote, RefMan)

TY  - JOUR
AB  - As a methodology complementary to acoustic analogy, the asymptotic approach to aeroacoustics seeks to predict aerodynamical noise on the basis of first principles by probing into the physical processes of acoustic radiation. The present paper highlights the principal ideas and recent developments of this approach, which have shed light on some of the fundamental issues in sound generation in shear flows. The theoretical work on sound wave emission by nonlinearly modulated wavepackets of supersonic and subsonic instability modes in free shear flows identifies the respective physical sources or emitters. A wavepacket of supersonic modes is itself an efficient emitter, radiating directly intensive sound in the form of a Mach wave beam, the frequencies of which are in the same band as those of the modes in the packet. By contrast, a wavepacket of subsonic modes radiates very weak sound directly. However, the nonlinear self-interaction of such a wavepacket generates a slowly modulated mean-flow distortion, which then emits sound waves with low frequencies and long wavelengths on the scale of the wavepacket envelope. In both cases, the acoustic waves emitted to the far field are explicitly expressed in terms of the amplitude function of the wavepacket. The asymptotic approach has also been applied to analyse generation of sound waves in wall-bounded shear flows on the triple-deck scale. Several subtleties have been found. The near-field approximation has to be worked out to a sufficiently higher order in order just to calculate the far-field sound at leading order. The back action of the radiated sound on the flow in the viscous sublayer and the main shear layer is accounted for by an impedance coefficient. This effect is of higher order in the subsonic regime, but becomes a leading order in the transonic and supersonic regimes.
AU  - Wu,X
AU  - Zhang,Z
DO  - 10.1098/rsta.2019.0077
EP  - 18
PY  - 2019///
SN  - 1364-503X
SP  - 1
TI  - First-principle description of acoustic radiation of shear flows
T2  - Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
UR  - http://dx.doi.org/10.1098/rsta.2019.0077
UR  - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000510716400007&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
UR  - https://royalsocietypublishing.org/doi/10.1098/rsta.2019.0077
VL  - 377
ER  -
Download