Turbulent And Brownian Diffusive Deposition Of Aerosol Particles Onto A Rough Wall

Abstract

The diffusive deposition of aerosol particles onto a rough wall in a turbulent flow field has been experimentally studied, using a stirred tank having a sand-roughened inside wall and uncharged monodisperse particles of 0.01-0.2 μm diameter. The experimental results showed that the deposition rate of particles onto the rough surface is enhanced, as the roughness increases, compared with that onto a smooth surface. The enhancement depends upon size of particles, intensity of turbulence and roughness of the wall, and is found to be significant when particle size and turbulent intensity are large. To explain the mechanism of the deposition, a model in which the existence of a particle-free layer above the bottom of the roughened wall is assumed is presented. The enhancement of the deposition obtained in the experiments can be described well by this model, and the enhancement results mainly from turbulent diffusion near the wall. © 1987, The Society of Chemical Engineers, Japan. All rights reserved.