RESUSPENSION INDUCED BY IMPACTING PARTICLES

Ammonium fluorescein particles, 8.6-mu-m dia., were resuspended from a Tedlar surface by impacting 3.0-mu-m ammonium fluorescein particles from a 40 m s-1 jet. The time dependence of the reentrainment was measured with an optical counter and the spatial distribution of particles on the surface was measured at different stages of the reentrainment with an optical microscope and an image analyzer. The observed particle reentrainment from the area directly under the circular nozzle is accounted for by a theoretical calculation including the non-uniform profile of the particle beam and the non-uniform particle deposit on the impaction surface. Reentrainment from the area surrounding the nozzle was induced by particles which bounced from the central region and reimpacted at larger radial distances. This reentrainment is satisfactorily fitted by a calculation using trajectories inferred for the bouncing particles.