EFFECT OF PARTICLE SIZE AND MATERIAL PROPERTIES ON AERODYNAMIC RESUSPENSION FROM SURFACES

An experimental study of the aerodynamic entrainment of monodisperse spheres from glass substrates is presented. The spheres were made of ammonium fluorescein and polystyrene standards (MW=3700, 18,700, and 114,200 amu). The use of monosized particles with carefully controlled properties leads to a narrow distribution of spheresurface adhesion forces, facilitating the determination of the particle entrainment threshold. The spheres were exposed to well-characterized shear stresses in two different flows, (i) laminar channel flow; and (ii) a normally impinging gas jet. Threshold shear stresses were found to be more sensitive to particle size than predicted by the existing resuspension theories, which are based on equilibrium adhesion models. Furthermore, resuspension was also found to be sensitive to the duration of the applied shear stress. This sensitivity depends upon the particle size and material properties. A kinetic model of particle detachment is presented to account for these observed trends.