Electrohydrodynamic instability of two superposed Walters B´ viscoelastic fluids in relative motion through porous medium |
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Authors: | M F El-Sayed |
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Affiliation: | (1) Department of Mathematics and Computer Science, Faculty of Science, United Arab Emirates University, P.O. Box 17551 Al Ain, United Arab Emirates e-mail: m.elsayed@uaeu.ac.ae, AE |
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Abstract: | Summary The electrohydrodynamic Kelvin–Helmholtz instability of the interface between two uniform superposed viscoelastic (B′ model)
dielectric fluids streaming through a porous medium is investigated. The considered system is influenced by applied electric
fields acting normally to the interface between the two media, at which there are no surface charges present. In the absence
of surface tension, perturbations transverse to the direction of streaming are found to be unaffected by either streaming
and applied electric fields for the potentially unstable configuration, or streaming only for the potentially stable configuration,
as long as perturbations in the direction of streaming are ignored. For perturbations in all other directions, there exists
instability for a certain wavenumber range. The instability of this system can be enhanced (increased) by normal electric
fields. In the presence of surface tension, it is found also that the normal electric fields have destabilizing effects, and
that the surface tension is able to suppress the Kelvin–Helmholtz instability for small wavelength perturbations, and the
medium porosity reduces the stability range given in terms of the velocities difference and the electric fields effect. Finally,
it is shown that the presence of surface tension enhances the stabilizing effect played by the fluid velocities, and that
the kinematic viscoelasticity has a stabilizing as well as a destabilizing effect on the considered system under certain conditions.
Graphics have been plotted by giving numerical values to the parameters, to depict the stability characteristics.
Received 27 March 2000; accepted for publication 3 May 2001 |
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Keywords: | Hydrodynamic Stability non-Newtonian Fluid Flow Porous Medium Electrohydrodynamics |
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