Key points are not available for this paper at this time.
We introduce a well-defined geometrical parameter, , related to dynamically connected pore sizes in composite materials. describes the effects of an internal boundary layer on a variety of processes including electrical surface conduction, high-frequency viscous damping of acoustic waves, and healing length effects in fourth sound. We argue that is also related to the dc permeability to flow of a viscous fluid.
Johnson et al. (Mon,) studied this question.