Imperial College London
Professor Xuesong Wu

ProfessorXuesongWu

Faculty of Natural Sciences, Department of Mathematics

Professor of Applied Mathematics
 
 
 
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Contact

 

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

 
 
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Location

 

738Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Qin:2016:10.1017/jfm.2016.287,
author = {Qin, F and Wu, X},
doi = {10.1017/jfm.2016.287},
journal = {Journal of Fluid Mechanics},
pages = {874--915},
title = {Response and receptivity of the hypersonic boundary layer past awedge to free-stream acoustic, vortical and entropy disturbances},
url = {http://dx.doi.org/10.1017/jfm.2016.287},
volume = {797},
year = {2016}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - This paper analyses the response and receptivity of the hypersonic boundary layerover a wedge to free-stream disturbances including acoustic, vortical and entropyfluctuations. Due to the presence of an attached oblique shock, the boundary layer isknown to support viscous instability modes whose eigenfunctions are oscillatory in thefar field. These modes acquire a triple-deck structure. Any of three elementary typesof disturbances with frequency and wavelength on the triple-deck scales interacts withthe shock to generate a slow acoustic perturbation, which is reflected between theshock and the wall. Through this induced acoustic perturbation, vortical and entropyfree-stream disturbances drive significant velocity and temperature fluctuations withinthe boundary layer, which is impossible when the shock is absent. A quasi-resonancewas identified, due to which the boundary layer exhibits a strong response to a continuumof high-frequency disturbances within a narrow band of streamwise wavenumbers.Most importantly, in the vicinity of the lower-branch neutral curve the slow acousticperturbation induced by a disturbance of suitable frequency and wavenumbers is inexact resonance with a neutral eigen mode. As a result, the latter can be generated directlyby each of three types of free-stream disturbances without involving any surfaceroughness element. The amplitude of the instability mode is determined by analysingthe disturbance evolution through the resonant region. The fluctuation associatedwith the eigen mode turns out to be much stronger than free-stream disturbances dueto the resonant nature of excitation and in the case of acoustic disturbances, to thewell-known amplification effect of a strong shock. Moreover, excitation at the neutralposition means that the instability mode grows immediately without undergoingany decay, or missing any portion of the unstable region. All these indicate that thisnew mechanism is particularly efficient. The boundary-layer response and c
AU  - Qin,F
AU  - Wu,X
DO  - 10.1017/jfm.2016.287
EP  - 915
PY  - 2016///
SN  - 0022-1120
SP  - 874
TI  - Response and receptivity of the hypersonic boundary layer past awedge to free-stream acoustic, vortical and entropy disturbances
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2016.287
UR  - http://hdl.handle.net/10044/1/32495
VL  - 797
ER  -
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