Time-dependent particle transport through granular filters

This paper describes an analytical model of filtration for granular media, based on the mechanics of particle migration under hydraulic loads. A new e quation to predict the probability of particle movement through a 3D networ k model of the filter voids has been developed. Void constriction sizes are determined based on the particle-size distribution and relative density of the filter. An important new development is the differentiation between pa rticles that form part of the filter structure and fine particles that are loose within the filter voids, or coarse particles that are enmeshed in a m atrix of fines. The rate of particle erosion and transport is governed by t he consideration of mass and momentum conservation. The model describes the time-dependent change of flow rate and base and filter particle-size distr ibution, porosity, and permeability. The model has application in the desig n of granular filters for noncohesive uniform, well-, and broadly graded ba se and filter materials.