JOURNAL OF COLLOID AND INTERFACE SCIENCE 204, 24–32 (1998) ARTICLE NO. CS985521 Turbulent Resuspension of Small Nondeformable Particles Mihalis Lazaridis,* ,1 Yannis Drossinos, * and Panos G. Georgopoulos² * European Commission, Joint Research Centre, I-21020 Ispra (VA), Italy; and ² Environmental and Occupational Health Sciences Institute, Rutgers University, and University of Medicine and Dentistry of New Jersey, 170 Frelinghuysen Road, Piscataway, New Jersey 08855-1179 Received July 8, 1997; accepted March 16, 1998 greater than the adhesive forces. Extensions of this method An energy-balance resuspension model is modified and applied have included particle rolling and sliding (1), and, more to the resuspension of a monolayer of nondeformable spherical importantly, the stochastic origin of resuspension has been particles. The particle–surface adhesive force is calculated from incorporated by postulating that removal forces are not con- a microscopic model based on the Lennard-Jones intermolecular stant in time (4, 5). Rather, they are considered to be inter- potential. Pairwise additivity of intermolecular interactions is as- mittent (6) because they are assumed to be due to turbulent sumed and elastic flattening of the particles is neglected. From bursts that penetrate the viscous sublayer of the turbulent the resulting particle–surface interaction potential the natural fre- boundary layer. The stochastic nature of resuspension has quency of vibration of a particle on a surface and the depth of the been emphasized since experiments show that particle resus- potential well are calculated. The particle resuspension rate is pension is not instantaneous but time-dependent. Force-bal- calculated using the results of a previously developed energy-bal- ance model, where the influence of fluid flow on the bound particle ance models underestimate the resuspension rate (7, 8), and motion is recognized. The effect of surface roughness is included by they neglect energy transfer from the turbulent fluid to a introducing an effective particle radius that results in log-normally bound particle. For a recent review of current theoretical distributed adhesive forces. The predictions of the model are com- and experimental work on particle resuspension see Ziskind, pared with experimental results forthe resuspension of Al 2 O 3 par- Fichman, and Gutfinger (9). ticles from stainless steel surfaces.  1998 Academic Press Reeks, Reed, and Hall (7) proposed a different approach Key Words: resuspension;energy-balance model;Lennard-Jones to particle resuspension by developing a model ( hereafter interaction; adhesion. referred to as the RRH model) based on an energy-balance approach. A deposited particle is considered to be bound to the surface by an anharmonic potential. At equilibrium, i.e., 1. INTRODUCTION in the absence of fluid flow, the particle remains at the bot- tom of the potential well. In the presence of turbulent flow, Particle resuspension due to turbulent fluid flow is im- the fluid transfers energy to the particle via turbulent eddies, portant in the interaction of the atmosphere with various thereby causing the particle to oscillate in the potential well. surfaces and in numerous industrial processes. For example, When the particle has accumulated enough energy to escape in the nuclear industry, fission-product aerosols released dur- from the potential well, it resuspends. Hence, energy trans- ing a postulated severe accident in a Light Water Reactor fer, due to turbulent eddies and most efficient at frequencies may deposit and resuspend repeatedly in the vessel circuit close to the natural frequency of vibration of the particle, and containment. Consequently, resuspension can have a leads to particle detachment and resuspension. strong effect on the timing and magnitude of the radioactive A modification of the RRH model has been proposed source released to the containment and the environment. recently (10) (revised RRH model), where the effect of Particle resuspension is important in other areas, for exam- the drag force on the resuspension rate has been included. ple, in the semiconductor industry (1), in autocatalytic dust Whereas in the original RRH model particle oscillations are explosions (2), and in contributing to erosion of soil and perpendicular to the surface, in the revised model the parti- river beds (3). cle, under the action of the drag force, oscillates about a Current models of particle resuspension are based either pivot. This revised model gives improved agreement with on force- or energy-balance models. In force-balance models experimental results. In the present paper we follow the resuspension occurs when aerodynamic lift forces become approach of the initial RRH model without considering the effect of the drag force. We show that a modification of the interaction potential of the initial RRH model improves the 1 To whom correspondence should be addressed at Norwegian Institute for Air Reseach (NILV) Instittutveien 18, Box 100, Kjeller, N-2007 Norway. agreement of its predictions with experimental data. 24 0021-9797/98 $25.00 Copyright  1998 by Academic Press All rights of reproduction in any form reserved.