Two-Phase Flow in Porous Media: Scaling of Steady-State Effective   Permeability
  A recent experiment has considered the effective permeability of two-phase flow of air and a water-glycerol solution under steady-state conditions in a two-dimensional model porous medium, and found a power law dependence with respect to capillary number. Running simulations on a two-dimensional network model a similar power law is found, for high viscosity contrast as in the experiment and also for viscosity matched fluids. Two states are found, one with stagnant clusters and one without. For the stagnant cluster state, a power law exponent 0.50 is found for viscosity matched fluids and 0.54 for large viscosity contrast. When there are no stagnant clusters the exponent depends on saturation and varies within the range of 0.67 - 0.80. 
Morten Gr{\o}va
physics.flu-dyn cond-mat.soft physics.comp-ph