Rheology of High-Capillary Number Flow in Porous Media
  Immiscible fluids flowing at high capillary numbers in porous media may be
characterized by an effective viscosity. We demonstrate that the effective
viscosity is well described by the Lichtenecker-Rother equation. The exponent
$\alpha$ in this equation takes either the value 1 or 0.6 in two- and 0.5 in
three-dimensional systems depending on the pore geometry. Our arguments are
based on analytical and numerical methods.
