Effect of terminal velocities on macroscopic and microscopic hydrodynamic mixing of stratified suspensions.

We performed numerical experiments to investigate the mixing of stratified suspensions composed of different particle types by gravitational sedimentation. The mixing process is controlled by a dimensionless group Y_{m}∼U_{f}/U_{St1}, where U_{f} is a typical velocity of a macroscopic sedimenting finger and U_{St1} is the Stokes settling velocity of a single spherical particle in the upper suspension. The effects of components of Y_{m}, in particular, terminal velocities of particles, were investigated.

The Effect of the Layered Internal Structure of Fibrous Beds on the Hydrodynamic Diffusive Behavior of Microparticles.

To separate and collect microparticles such as cells, the behavior of particles in fibrous filters was investigated. It is essential to understand, in detail, the motion of particles in microscale flows, because is often small, and particles exhibit complex behaviors such as changes in relative position and spreading owing to hydrodynamic interactions. We calculated the motion of microparticles passing through the fibrous bed using the Stokesian dynamics method, in which hydrodynamic interaction is considered, theoretically.

Diffusive behavior of a thin particle layer in fluid by hydrodynamic interaction.

The hydrodynamic effect on a thin particle layer, which moves relative to fluid by an external force, is investigated theoretically and numerically. Because of the presence of layer ends, the arrangement of particles in the layer is anisotropic and the drag force acting on them varies according to the position. The resulting relative motion of particles brings about the spreading of the layer.