Elements of Fractal Generalization of Dual‐Porosity Model for Solute Transport in Unsaturated Fractured Rocks

In this study, new elements were developed to generalize the dual-porosity model for moisture infiltration on and solute transport in unsaturated rocks, taking into account fractal aspects of the percolation process. Random advection was considered as a basic mechanism of solute transport in self-similar fracture systems. In addition to spatial variations in the infiltration velocity field, temporal fluctuations were also taken into account. The rock matrix, a low-permeability component of the heterogeneous geologic medium, acts as a trap for solute particles and moisture. Scaling relations were derived for the moisture infiltration flux, the velocity correlation length, the average velocity of infiltration, and the velocity correlation function. The effect of temporal variations in precipitation intensity on the infiltration processes was analyzed. It showed that the mode of solute transport is determined by the power exponent in the advection velocity correlation function and the dimensionality of the trapping system, both of which may change with time. Therefore, depending on time, various transport regimes may be realized: superdiffusion, subdiffusion, or classical diffusion. The complex structure of breakthrough curves from changes in the transport regimes was also examined. A renormalization of the solute source strength due to characteristic fluctuations of highly disordered media was established

Permeability of Microporous Carbon Preforms

The permeability of microporous amorphous carbon preforms with varying pore size and pore distributions has been experimentally examined. The porous structures have been characterized by mercury porosimetry and by quantitative metallography of pressure-infiltration-cast metal matrix composites based on the carbon preforms. The permeability shows a linear correlation with the fraction porosity and the square of the pore diameter