Dispersion at the interface of miscible liquids in a soil

When two miscible liquids flow through a porous medium (e.g., fresh water and salt water in an aquifer), the dispersion at the interface is described by Fick's law with a velocity‐dependent coefficient. In the first part of this paper, the horizontal flow of two liquids is used to demonstrate that the influence of gravity and the effects of the differences in density and viscosity are usually negligible. Then solutions are presented for the dispersion at the interface of liquids in two‐dimensional flow.