Molecular diffusion in periodic porous media

The diffusion of fluid through a porous medium was modeled for a periodic array. The time dependent bulk effective diffusion coefficient D(t) was calculated using Bloch type eigenfunctions. The calculations were made for periodic media composed of octahedron-like obstacles which ranged from completely separated to highly overlapping obstacles (porosity of 3%). The calculation of D(t) involves evaluation of the nuclear magnetic resonance pulsed field gradient spin echo amplitude M(k,t), which is a measurable quantity. The method, which is most effective for long times, produces results which also agree with short time asymptotics. This method is applicable for any periodic microgeometry and virtually any porosity. © 2000 American Institute of Physics.