The Entrainment of Particles by a Turbulent Spot in a Laminar Boundary Layer

Abstract

The entrainment of solid particles from a flat surface by an artificially generated turbulent spot in a laminar boundary layer in a wind tunnel was studied. High-speed films of the entrainment process revealed two different entrainment forms: direct entrainment for larger particles and entrainment after piling of the leading edge of the particle bed for small, strongly cohesive particles. A theoretical model for the entrainment process was developed based on the presence of turbulent bursts in the spot. Good agreement was found between model predictions and the results of particle sampling experiments.