Lateral Migration Velocity Research Articles

Particle Migration in a Helle-Shaw Cell with Non-Parallel Walls

Motion of a single macroscopic particle in a liquid flowing through a narrow channel with slightly non-parallel walls is studied by a visualization method. The experiment is limited to the region of slight inertia effects, Ar < 500. Three kinematic characteristics of the particle motion in the channel, viz. settling velocity in a still liquid, as well as longitudinal and lateral migration velocities under non-zero flow, are determined and correlated in dependence on the operation parameters. Both the longitudinal characteristics strongly depend on the particle-to-channel size ratio and are only slightly affected by inertia effects. On the other hand, the inertia effects play an essential role in the mechanism of lateral migration.

Viscous interactions of many neutrally buoyant spheres in Poiseuille flow

A theory is developed to predict the motion of N neutrally buoyant spheres suspended in laminar flow between parallel plates. The spheres are at large separation yet nearer each other than the duct walls, and the Reynolds number is small. In this parameter range, viscous interactions are larger than inertial effects, and can be represented in terms of a superposition of ‘strainlets’. Several examples are given to show this viscous interaction effect. Near the leading edge of a front of spheres or near the trailing edge significant lateral migration velocities can occur, being at least one order of magnitude larger than inertially induced migration velocities. This phenomenon may have a negative effect on ‘chromatographic’ separation schemes, affecting particle concentration, recovery and resolution.