ELECTROHYDRODYNAMIC INSTABILITY OF 2 SUPERPOSED VISCOUS STREAMING FLUIDS THROUGH POROUS-MEDIA

The electrohydrodynamic instability of the plane interface between two uniform, superposed viscous streaming dielectric fluids through porou s media is considered in the presence of a horizontal electric field. In the absence of surface tension, perturbations transverse to the dir ection of streaming are found to be unaffected by either the presence of streaming or an electric field as long as perturbations in the dire ction of streaming are ignored. Whereas for perturbations in all other directions there exists instability for a certain wave-number range. The instability of this system can be delayed by the presence of a tan gential electric field. Both the electric field and surface tension ar e able to suppress Kelvin-Helmholtz instability for small wavelength p erturbations and the medium porosity reduces the stability range given in terms of a difference between the streaming velocities and the ele ctric-field effect. For the case in which the heavier fluid overlies t he lighter one, it is found that both surface tension and the tangenti al electric field succeed in stabilizing a certain wave-number range t hat was unstable in their absence.