Electrohydrodynamic instability of miscible core-annular flows with electrical conductivity stratification
Wong, Teck Neng
Date of Issue2015
School of Mechanical and Aerospace Engineering
This paper investigates the electrohydrodynamical instability of two miscible flows in a micro-pipe subject to an axial electric field. There is an electrical conductivity stratification between the two layers. A weak shear flow arises from a constant axial pressure gradient. The three-dimensional linear stability analysis is studied under the assumption of a quasi-steady state. The influences of the conductivity ratio η, the interface location a, the interface thickness δ, the Reynolds number Re and the Schmidt number Sc on the linear stability of the flows are investigated. The flow becomes more unstable for a larger conductivity contrast. When the conductivity in the inner layer is larger, the critical unstable mode can be dominated by either the corkscrew mode (the azimuthal wavenumber m=1) or the axisymmetric mode (m=0), which is dependent on the interface location a. It is observed that, when the interface is proximal to pipe’s wall, the critical unstable mode shifts from the corkscrew mode to the axisymmetric mode. When the conductivity is larger in the outer layer, the instability is dominated by the axisymmetric mode. A detailed parametric study shows that the flow is least stable when the interface between the two liquids is located at approximately a=0.3 and a=0.2 for conductivity ratios of η=0.5 and η=2 respectively. The flow becomes more stable as the interface becomes thicker, and the shear flow and ionic diffusion are found to have a stabilizing effect due to the enhancement of dissipation mechanisms.
DRNTU::Engineering::Mechanical engineering::Fluid mechanics
Journal of fluid mechanics
© 2015 Cambridge University Press. This paper was published in Journal of Fluid Mechanics and is made available as an electronic reprint (preprint) with permission of Cambridge University Press. The paper can be found at the following official DOI: [http://dx.doi.org/10.1017/jfm.2014.720]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.