Particle pushing: the concentration of particles near a solid interface during downward flow

Abstract

We have measured the distribution of insoluble particles within a few millimeters of the tube wall in a downward flowing liquid in order to verify that the velocity gradient mechanism for particle pushing works for particles less than a few hundred microns in diameter. The experimental results show that particles that are denser than the liquid concentrate near the tube wall whereas particles less dense than the liquid migrate away from the wall, leaving a particle deficient layer near the surface, confirming the velocity gradient mechanism. The experimental results have been modelled using the velocity gradient mechanism and the model is in good agreement with experimental results. Calculation shows that the concentration of particles near a solid surface depends on the density and size of the particles, the flow speed and the distance from the inlet of the flow.