Dispersion in Anisotropic, Homogeneous, Porous Media

Abstract

A tensor model for the dispersion coefficient for saturated flow in anisotropic, homogeneous porous media is proposed. The tensor components are evaluated from experiments with an anisotropic, homogeneous porous medium, constructed from thin, alternating layers of two types of sand, having different mean particle sizes. Tests were conducted for flow parallel, perpendicular, and inclined at 60° to the direction of the layers. The hydraulic conductivity and the longitudinal dispersion coefficient were found to be second‐rank tensors with equal and constant eccentricities and with major and minor principal axes oriented along and perpendicular to the direction of the sand layers, respectively. The lateral dispersion coefficient was found to be a second‐rank tensor whose principal axes were orthogonal to those of the hydraulic conductivity tensor and whose eccentricity increased with increasing seepage velocity. Two values of the off‐principal diagonal dispersivities were found to be nearly equal in magnitude but opposite in sign. Experimental results support the dispersion coefficient tensor model proposed in the investigation.