| Collection of particles by fibrous filters in the presence of an external electric field has been studied. A numerical method for solving the particle trajectories was developed using the full Navier-Stoke equations. In the present study the influence of the externally applied electric field on dendrite formation was also considered. A staggered array of cylinders was used as a model of a fibrous filter. A typical cell within the filter is defined. Particles enter the cell at random locations through the upstream face. The trajectory of each particle is computed numerically. The location of the particle within the cell is continuously checked. If the particle is deposited, either on a fiber or on an already deposited particle, its final location is recorded.; Using this model, filtration efficiencies of fibrous filters with packing densities ranging from 0.0194 to 0.0982 were calculated. Particles in the 0.5 to 1.25 micron range were used and filtration velocities were varied between 1.0 and 100.0 cm/s. The strength of the electric field was set at 1.0 x 10('4) V/cm for the enhanced cases. Three-dimensional graphical representations of the simulation, with and without electric field, are presented and the difference in structures discussed. Good agreement between simulated dendrites with experimental observations was obtained. |
