A Simple Model for Deep Bed Filtration
  We present a simple model for deep bed filtration, where particles suspended in a fluid are trapped while passing through a porous filter. A steady state of the model is reached when filter can not trap additional particles. We find the model has two qualitatively different steady states depending on the fraction of traps, and the steady states can be described by directed percolation. We study in detail the evolution of the distribution of trapped particles, as the number of trapped particles increases. To understand the evolution, we formulate a mean field equation for the model, whose numerical solution is consistent with the behavior of the model. We find the trapped particle distribution is insensitive to details of the formulation of the model. 
Jysoo Lee and Joel Koplik (Levich Institute, City College of New York)