Transport of sedimenting Brownian particles in a rotating Poiseuille flow

Abstract

Generalized Taylor dispersion theory is used to analyze the convective and diffusive transport of sedimenting colloidal particles occurring within a Poiseuille flow in a horizontal circular pipe that is being rotated slowly about its symmetry axis. Such rigid-body rotation serves to keep the particles permanently in suspension despite their non-neutral buoyancy, thereby preventing deposition of the particles on the cylinder bottom. In the ‘‘large’’ particle limit, where transverse diffusion is small compared with sedimentation, expressions are derived for the mean axial velocity and Taylor dispersivity of the colloidal particles. A novel flow field fractionation (FFF) scheme based thereon is proposed for continuously separating particles of different sizes and/or densities.