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Instability of a free-shear layer in the vicinity of a viscosity-stratified layer

Published online by Cambridge University Press:  11 July 2014

Kirti Chandra Sahu*
Department of Chemical Engineering, Indian Institute of Technology Hyderabad, Yeddumailaram 502205, India
Rama Govindarajan
TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research Narsingi, Hyderabad 500075, India
Email address for correspondence:


The stability of a mixing layer made up of two miscible fluids, with a viscosity-stratified layer between them, is studied. The two fluids are of the same density. It is shown that unlike other viscosity-stratified shear flows, where species diffusivity is a dominant factor determining stability, species diffusivity variations over orders of magnitude do not change the answer to any noticeable degree in this case. Viscosity stratification, however, does matter, and can stabilize or destabilize the flow, depending on whether the layer of varying velocity is located within the less or more viscous fluid. By making an inviscid model flow with a slope change across the ‘viscosity’ interface, we show that viscous and inviscid results are in qualitative agreement. The absolute instability of the flow can also be significantly altered by viscosity stratification.

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© 2014 Cambridge University Press 

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