Numerical Investigation of Viscous Flow Fields Around Multifiber Filters

Fibrous filters have been used in the filtration of particles for a long time. One way to help us understand more about fibrous filters is to perform model simulations and study how particles become attached to the fibers. Most existing models are basically single-fiber models. Although a few models solve flow fields past many fibers, the use of the Stokes equations and artificial boundary conditions limits their solutions to be only approximations of real flows. In the present study, multifiber models have been developed. Flow fields around arrays of parallel and staggered fibers are computed by solving the incompressible steady-state NavierStokes equations numerically. The results show that the viscous flow around the fibers becomes periodic immediately after the first fiber array from a filter entrance until it reaches the last fiber array. Because of fiber interaction, the flow may separate and form eddies downstream of a fiber and upstream of the subsequent fiber at very low Reynolds numbers. However, flow around an isolated circular fiber does not separate at Reynolds numbers smaller than 5 without such interaction. The Stokes equations, on the other hand, are not able to accurately describe such interaction for flow around many fibers. The results of this study agree well with available experimental results.