The motion of small spherical particles in a cellular flow field

In an earlier paper, Maxey and Corrsin [J. Atmos. Sci. 43, 1112 (1986)] studied the motion of small aerosol particles settling under gravity through an infinite, periodic, cellular flow field subject to the effects of a Stokes drag force and inertia of the particles. Particle inertia was shown to have an important influence on the motion: No permanent suspension in the flow occurred, particles generally settled more rapidly than in still fluid, and the particle paths merged into isolated asymptotic trajectories. This study is continued for particles that are not necessarily much denser than the surrounding fluid but vary in density. Two basic responses are identified: an aerosol response for particles denser than the fluid, similar to that mentioned, and a bubble response for particles less dense. For both, particle accumulation is still a recurring feature. Results of numerical simulations are discussed, together with the stability of equilibrium points and the role of particle or fluid inertia.