Diffusion and sedimentation of particles in inhomogeneous porous media

The diffusive sedimentation of particles in a porous inhomogeneous medium was considered. The transport of particles was described by a convective diffusion equation containing a term responsible for the sink of particles. The flow field of carrier gas was calculated by solving of the Darcy equation modified so as to take into account fluctuations in the permeability in the porous medium and the correlation between the sink of particles and the permeability. The mean concentrations and fluctuation field of particles were obtained. In the outflow from a porous layer, the mean concentration of particles depends substantially on the correlation function for fluctuations in the permeability of the medium. The dependences of the pressure drop and the filtering medium's efficiency on the correlation function of fluctuations in its porosity. Concrete results were obtained for fibrous aerosol filters. It was found that the effect of inhomogeneities in the structure on the performance criterion of the filter increases with the efficiency of particle trapping.