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:2021:10.1007/978-3-030-67902-6_33,
author = {Fung, L and Hwang, Y},
doi = {10.1007/978-3-030-67902-6_33},
journal = {IUTAM Bookseries},
pages = {379--389},
title = {Instability of tilted shear flow in a strongly stratified and viscous medium},
url = {http://dx.doi.org/10.1007/978-3-030-67902-6_33},
volume = {38},
year = {2021}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - It is well known that stratification can stabilise shear flow. In a vertical shear flow, the Miles-Howard’s criterion firmly indicates that flow should be stable if the local Richardson number is greater than one fourth. However, if shear is tilted with a non-zero angle from vertical, an instability can arise even under very strong stratification, and such an instability was recently observed in a titled wake flow at low Reynolds number (Meunier 2012, J. Fluid Mech., 699:174). In the present study, we showed that in the limit of low Froude number and low Reynolds number, the linearised equations of motion could 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 demonstrated that the low-Froude-number mode would be a horizontal inflectional instability, and should remain two dimensional at small tilting angles. It is further shown that the emergence of small vertical velocity at finite Froude number modifies the horizontal inflectional instability and leads to paradoxically stabilising buoyancy force on increasing Froude number. Finally, an absolute instability analysis is performed, revealing qualitatively good agreement with the experimental result.
AU  - Fung,L
AU  - Hwang,Y
DO  - 10.1007/978-3-030-67902-6_33
EP  - 389
PY  - 2021///
SN  - 1875-3507
SP  - 379
TI  - Instability of tilted shear flow in a strongly stratified and viscous medium
T2  - IUTAM Bookseries
UR  - http://dx.doi.org/10.1007/978-3-030-67902-6_33
UR  - http://arxiv.org/abs/1909.11376v1
UR  - http://hdl.handle.net/10044/1/82016
VL  - 38
ER  -
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