POTENTIOSTATIC ELECTROCONVECTION IN A LAYER AND IN A LOOP

This paper concerns electroconvectional stability of a conduction stat e in an electrolyte layer flanked by cation-permselective walls (elect rodialysis membranes, electrodes) under potentiostatic conditions. It is shown through a numerical finite difference solution of the linear stability problem that above a certain voltage threshold the basic con duction state becomes electroconvectionally unstable. Marginal stabili ty curves in the voltage/wave number plane are calculated and the depe ndence of the critical threshold characteristics on the system's param eters (ionic diffusivities ratio, electroconventional Peclet number) s tudied. Electroconvectional instability is shown to occur for an arbit rary ionic diffusivities ratio. A model problem of electroconvection i n a loop under potentiostatic conditions is solved explicitly for a st eady state. It is shown that above a certain voltage threshold; the qu iescent conduction in the loop bifurcates into a pair of electroconvec tional steady state circulations. (C) 1996 American Institute of Physi cs.