Imperial College London

ProfessorPeterSchmid

Faculty of Natural SciencesDepartment of Mathematics

Chair in Applied Mathematics
 
 
 
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Contact

 

peter.schmid

 
 
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Location

 

753Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@inproceedings{Karami:2018:1/012019,
author = {Karami, S and Stegeman, PC and Theofilis, V and Schmid, PJ and Soria, J},
doi = {1/012019},
publisher = {Institute of Physics (IoP)},
title = {Linearised dynamics and non-modal instability analysis of an impinging under-expanded supersonic jet},
url = {http://dx.doi.org/10.1088/1742-6596/1001/1/012019},
year = {2018}
}

RIS format (EndNote, RefMan)

TY  - CPAPER
AB - Non-modal instability analysis of the shear layer near the nozzle of a supersonic under-expanded impinging jet is studied. The shear layer instability is considered to be one of the main components of the feedback loop in supersonic jets. The feedback loop is observed in instantaneous visualisations of the density field where it is noted that acoustic waves scattered by the nozzle lip internalise as shear layer instabilities.A modal analysis describes the asymptotic limit of the instability disturbances and fails to capture short-time responses. Therefore, a non-modal analysis which allows the quantitative description of the short-time amplification or decay of a disturbance is performed by means of a local far-field pressure pulse. An impulse response analysis is performed which allows a wide range of frequencies to be excited. The temporal and spatial growths of the disturbances in the shear layer near the nozzle are studied by decomposing the response using dynamic mode decomposition and Hilbert transform analysis.The short-time response shows that disturbances with non-dimensionalised temporal frequencies in the range of 1 to 4 have positive growth rates in the shear layer. The Hilbert transform analysis shows that high non-dimensionalised temporal frequencies (>4) are dampened immediately, whereas low non-dimensionalised temporal frequencies (<1) are neutral. Both dynamic mode decomposition and Hilbert transform analysis show that spatial frequencies between 1 and 3 have positive spatial growth rates. Finally, the envelope of the streamwise velocity disturbances reveals the presence of a convective instability.
AU - Karami,S
AU - Stegeman,PC
AU - Theofilis,V
AU - Schmid,PJ
AU - Soria,J
DO - 1/012019
PB - Institute of Physics (IoP)
PY - 2018///
SN - 1742-6588
TI - Linearised dynamics and non-modal instability analysis of an impinging under-expanded supersonic jet
UR - http://dx.doi.org/10.1088/1742-6596/1001/1/012019
UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000454926900019&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
UR - http://hdl.handle.net/10044/1/67156
ER -