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Linear stability of plane Poiseuille flow of two superposed fluids

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TLDR
In this paper, the stability of two superposed fluids of different viscosity in plane Poiseuille flow is studied numerically and conditions for the growth of an interfacial wave are identified.
Abstract
Stability of two superposed fluids of different viscosity in plane Poiseuille flow is studied numerically. Conditions for the growth of an interfacial wave are identified. The analysis extends Yih’s results [J. Fluid Mech. 27, 337 (1967)] for small wavenumbers to large wavenumbers and accounts for differences in density and thickness ratios, as well as the effects of interfacial tension and gravity. Neutral stability diagrams for the interfacial mode are reported for a wide range of the physical parameters describing the flow. The analysis shows also that the flow is linearly unstable to a shear mode instability. The dependence of the critical Reynolds number for the shear mode on the viscosity ratio is reported. Theoretical predictions of critical Reynolds numbers for both modes of instability are compared with available experimental data.

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References
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TL;DR: In this article, the authors present a review of the latest developments as well as earlier work in this area, organized into the following categories: Taylor-Couette flows, instabilities in cone and plate-and-plate flows, parallel shear flows, extrudate distortions and fracture, Instabilities in shear flow with interfaces, extensional flows, and thermohydrodynamic instabilities.
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A note on the relation between temporally-increasing and spatially-increasing disturbances in hydrodynamic stability

TL;DR: In this paper, the frequency and amplification rates for a disturbance growing with respect to time are compared with those of a spatially growing wave having the same wave number, and it is shown that the frequencies are equal to a high order of approximation.
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Shear-flow instability at the interface between two viscous fluids

TL;DR: In this paper, the authors considered the linear stability of the cocurrent flow of two fluids of different viscosity in an infinite region and solved the problem using both numerical and asymptotic techniques.