EFFECT OF NORMAL ELECTRIC-FIELDS ON KELVIN-HELMHOLTZ INSTABILITY FOR POROUS-MEDIA WITH DARCIAN AND FORCHHEIMER FLOWS

The linear electrohydrodynamic Kelvin-Helmholtz instability of the int erface between two dielectric fully saturated porous media under the e ffect of normal electric fields is considered. The lighter fluid is ab ove the heavier one so that in the absence of both motion and electric fields, the arrangement is stable and the interface is flat. It is sh own that when the fluids are moving parallel to each other at differen t velocities, the interface may become unstable, and the normal electr ic fields have usually destabilizing effect. The corresponding conditi ons for marginal stability are derived for Darcian and Forchheimer flo ws. In both the cases, the velocities, and the electric fields should exceed some critical values in order for the instability to manifest i tself. In the case of Darcy's flow, however, an additional condition, involving the fluids viscosities, their density ratios and the electri c field values is required. (C) 1998 Published by Elsevier Science B.V . All rights reserved.