EFFECTIVE TRANSPORT-COEFFICIENTS IN HETEROGENEOUS MEDIA

The paper emphasizes the commonality of a number of transport phenomena in heterogeneous media. The computation of an effective transport coefficient is then illustrated by Monte Carlo simulation of the diffusion of a gas molecule in a porous solid. Both physical and stochastic descriptions of molecular motion in a porous solid are presented, the latter being more rigorous and presenting a different insight into the concept of tortuosity. The Monte Carlo simulations yielded results that are consistent with classical predictions for effective transport coefficients. The consistency was maintained even at low volume fractions of the conducting phase which are beyond the limit of validity of the assumptions made in classical predictions.