Electrical conduction and formation factor in isotropic porous media

A macroscopic form of Ohm's law is obtained for isotropic porous media saturated with an electrically conductive fluid by using volumetric averaging concepts. Closure of the macroscopic charge transport equation is aided by approximative modelling of the average geometric structures of three different types of isotropic porous media, namely foamlike materials, granular media and crossflow over prismatic bundles. Modelling of the microscopic charge transport necessitated the introduction of a representative interstitial flux of charge carriers and required quantification of the geometric tortuosity applicable to transport phenomena in general. Deterministic expressions for the formation factor are obtained and compare favourably with experimental results. Copyright (C) 1996 Elsevier Science Limited