Boundary and concentration effects on sedimentation of a liquid aerosol dispersion

摘要

An analytical study is presented for the quasi-steady sedimentation of a suspension of identical fluid aerosol spheres, as well as the sedimentation of a fluid aerosol particle in a spherical cavity pore. The Knudsen and Reynolds numbers are assumed small, so that the fluid flows, inside and outside the fluid particle, can be described by a continuum model with a hydrodynamic slip at the particle and cell wall surfaces, and the flow fields can be governed by the Stokes equations In addition, a unit cell model is applied to predict the hydrodynamic behavior of a monodispersed system for the spherical aerosol droplets. Two different boundary conditions at the shell of a unit cell are discussed: slip wall (Happel-type cell is included) and Kuwabara-type cell. Our analytical expressions of the average sedimentation velocity of particles are obtained in a closed form as functions of the particle volume fraction. The particle mobility is strongly influenced by the surface properties at the droplet-fluid interface and at the fictitious cell wall. Also, it is found that the particle motion deviates from isolated behavior by the change of internal-to-external viscosity ratio of the droplet, although the effect due to the viscosity ratio is still a weaker function in comparison with the influence of surface properties. In general, as the volume fraction of the dispersed fluid spheres increases, the influence of the concentration effect of the particles on the mean translational velocity becomes more significant. [References: 28]