Air injection into groundwater (air sparging) in a homogeneous axially
symmetric porous medium is modeled using a two-phase flow approach. A
numerical method based on the mixed form of the Richards equation for
both phases is presented. Furthermore two analytical approximations a
re discussed to explain the numerical results. One is a one-dimensiona
l description explaining the occurrence of small air saturations. The
other is a closed form approximation for the distribution of the air s
aturation in the resulting steady state. From the latter we can estima
te the maximum radius of influence of air sparging, as a function of t
he physical parameters. The analytical approximation at steady state a
nd the numerical results are in good agreement.