Formation of Wall Particle Layers by Simultaneous Deposition and Reentrainment of Fine Particles in Turbulent Aerosol Flows

• Published in: KAGAKU KOGAKU RONBUNSHU Vol. 19; no. 2; pp. 251 - 257
• Main Authors: Matsusaka, Shuji, Shimizu, Masanobu, Masuda, Hiroaki
• Format: Journal Article
• Language: English; Japanese
• Published: Tokyo The Society of Chemical Engineers, Japan 1993; Kagaku Kōgaku Kyōkai
• Subjects: Aerosol; article Layer Formation; Deposition; Reentrainment; Turbulent Flow
• ISSN: 0386-216X; 1349-9203
• DOI: 10.1252/kakoronbunshu.19.251

Formation of wall particle layers by simultaneous deposition and reentrainment was investigated for turbulent aerosol flows. Fine powder (mass median diameter=3 μm) was dispersed in an air flow and led into a circular glass tube. The process of particle layer formation was continuously observed and the mass of particles deposited on the wall was measured. Although the particle layers formed at low velocities uniformly covered the whole of the inside wall, they gradually changed into striped patterns at high velocities. It was found that the thickness of the particle layer decreases with increasing friction velocity of the flow, and is equal to the distance from the wall corresponding to a certain air velocity in a viscous sub-layer. The deposition patterns in their equilibrium states are determined only by the flow velocity, irrespective of the initial state. It was also found that the growth rate of particle layers has the maximum value for the variation of average aerosol velocity, because both the deposition flux and reentrainment flux increase with increasing velocity when it exceeds the critical reentrainment velocity.