Existence of two distinctly different spatial scales allows
one to compute Deff based on the principle of homogenization
(32,25). The method is an alternative to microscopic
particle tracking mimicked by Monte Carlo simulations
and is equivalent to determining effective diffusion coefficients
from Fick’s law: the steady-state diffusive flux is
measured as a function of the concentration difference maintained
between the opposite sides of a large rectangular box.
Mathematically, homogenization is an asymptotic analysis
that utilizes a small parameter, the ratio of micro- and
macro-length scales, to obtain accurate effective characteristics
of the medium (35).