Imperial College London
Alternate

Dr. Yongyun Hwang

Faculty of Engineering, Department of Aeronautics

Reader in Fluid Mechanics
 
 
 
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Contact

 

+44 (0)20 7594 5078y.hwang

 
 
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Location

 

337City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Fung:2020:10.1007/s42791-020-00030-8,
author = {Fung, L and Hwang, Y},
doi = {10.1007/s42791-020-00030-8},
journal = {JMST Advances},
pages = {37--51},
title = {Linear instability of tilted parallel shear flow in a strongly stratified and viscous medium},
url = {http://dx.doi.org/10.1007/s42791-020-00030-8},
volume = {2},
year = {2020}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - A linear stability analysis is performed on a tilted parallel wake in a strongly stratified fluid at low Reynolds numbers. A particular emphasis of the present study is given to the understanding of the low-Froude-number mode observed by the recent experiment (Meunier in J Fluid Mech 699:174–197, 2012). In the limit of low Froude number, the linearised equations of motion can be reduced to the Orr–Sommerfeld equation on the horizontal plane, except the viscous term that contains vertical dissipation. Based on this equation, it is proposed that the low-Froude-number mode would be a horizontal inflectional instability and should remain two-dimensional at small tilting angles as long as the Reynolds number is sufficiently low. To support this claim, the asymptotic regime where this analysis is strictly valid is subsequently discussed in relation to previous work on the proper vertical length scale. The absolute and convective instability analysis of parallel wake is further performed, showing qualitatively good agreement with the experimental result. The low-Froude-number mode is found to be stabilised on increasing Froude number, as in the experiment. It is shown that the emergence of small vertical velocity at finite Froude number, the size of which is proportional to the square of Froude number, plays the key role in the stabilisation by modifying the inflectional instability and paradoxically creating stabilising buoyancy effect with the increase of Froude number.
AU  - Fung,L
AU  - Hwang,Y
DO  - 10.1007/s42791-020-00030-8
EP  - 51
PY  - 2020///
SN  - 2524-7905
SP  - 37
TI  - Linear instability of tilted parallel shear flow in a strongly stratified and viscous medium
T2  - JMST Advances
UR  - http://dx.doi.org/10.1007/s42791-020-00030-8
UR  - https://link.springer.com/article/10.1007%2Fs42791-020-00030-8
UR  - http://hdl.handle.net/10044/1/79204
VL  - 2
ER  -
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