Control of non-spherical microparticles with center of gravity offset by a shear flow

The dynamics of sedimenting non-spherical particles with center of gravity offset in a shear flow is analyzed numerically using a dumbbell model. The calculation is performed by the method based on the Stokesian dynamics which accounts for multiple-body hydrodynamic interparticle interactions based on the Stokes equation. A dumbbell is found to rotate or glide, depending on the center of gravity offset ε and the strength of the shear flow. In the rotating motion, the particle rotates and falls vertically, accompanied by a periodical horizontal drift. In the gliding motion, the particle orients and glides in a fluid, where the gliding angle is determined by ε. The difference in trajectories of a dumbbell according to ε indicates that the motion of non-spherical particles with center of gravity offset can be controlled by a shear flow. A computation is performed for a mixture of two kinds of dumbbells, i.e., ε = 0 and 0.5, falling in a shear flow, and these dumbbells are sorted into two groups according to ε.