A numerical model of fibrous filters containing deposit

This work is aimed at developing numerical methods to model the effects that particle deposit collected by fibrous filters has upon the flow field within the filter and hence upon further deposition. A numerical model of the flow field has been developed using the Boundary Element Method. The model contains a two-dimensional single fibre with the boundary conditions applied on the computational domain accounting for the neighbouring fibres. A layer of porous material is assumed to cover the fibre modelling deposited particulate. The width of the porous layer, which varies along the fibre surface, is defined by particle behaviour determined in earlier work, [Dunnett SJ, Clement CF, A numerical study of the effects of loading from diffusive deposition on the efficiency of fibrous filters. J Aerosol Sci 2006; 37: 1116–1139]. Once the flow field is known the motion of the particles in the flow is modelled. Small particles are considered where diffusion is the main mechanism by which they are captured by the fibres. Various situations are considered and the flow and particle behaviour investigated. In particular the effect of existing porous deposit on the fibres upon further deposition is studied.