paper

Flow Between Two Sites on a Percolation Cluster

arXiv:cond-mat/0004397 · doi:10.1103/PhysRevE.62.8270

Abstract

We study the flow of fluid in porous media in dimensions and 3. The medium is modeled by bond percolation on a lattice of sites, while the flow front is modeled by tracer particles driven by a pressure difference between two fixed sites (``wells'') separated by Euclidean distance . We investigate the distribution function of the shortest path connecting the two sites, and propose a scaling {\it Ansatz} that accounts for the dependence of this distribution (i) on the size of the system, , and (ii) on the bond occupancy probability, . We confirm by extensive simulations that the {\it Ansatz} holds for and 3, and calculate the relevant scaling parameters. We also study two dynamical quantities: the minimal traveling time of a tracer particle between the wells and the length of the path corresponding to the minimal traveling time ``fastest path'', which is not identical to the shortest path. A scaling {\it Ansatz} for these dynamical quantities also includes the effect of finite system size and off-critical bond occupation probability . We find that the scaling form for the distribution functions for these dynamical quantities for and 3 is similar to that for the shortest path but with different critical exponents. The scaling form is represented as the product of a power law and three exponential cutoff functions. We summarize our results in a table which contains estimates for all parameters which characterize the scaling form for the shortest path and the minimal traveling time in 2 and 3 dimensions; these parameters are the fractal dimension, the power law exponent, and the constants and exponents that characterize the exponential cutoff functions.

31 pages, 12 Figures

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