Particles migration in laminar boundary layer flow

The behavior of a suspension of neutrally buoyant solid particles in the moderate relative velocity region (close to the leading edge) in a laminar boundary layer along a flat plate, is investigated. The velocity fields of both the fluid and the solid particles and the density distribution of the solid particles are simultaneously obtained by the use of the Laser-Doppler technique.It is shown that in this longitudinal region of the two-phase suspension boundary layer, the solid particles which initially lead the fluid decelerate as they move downstream, until at a certain vertical distance they lag the fluid. Clearly defined one-way transverse migration of particles directed away from the plate is characteristic of this region.