Abstract
The present work deals with the resuspension of small nondeformable particles from multilayer deposits in a turbulent boundary layer. A kinetic force-balance approach was adopted to model particle motion at the point of detachment, whereby intermolecular interactions were modeled by the Lennard-Jones potential. The rate of change of the number of particles was estimated for each discrete layer based on existing kinetic models. In particular, the kinetic equations of Lazaridis and Drossinos (1998), LD, and Friess and Yadigaroglu (2001), FY, were implemented and compared using lattice arranged deposits. The influence of exposure time and friction velocity was investigated through the obtained resuspension rates. It was found that the single-layer resuspension rates were substantially affected by the layer position within the deposit as well as considerably influenced by both the exposure time and the friction velocity. Moreover, the numerical results demonstrate that the LD kinetic estimates higher resuspension rates compared to the FY kinetic only for short exposures to the flow, predominantly due to a different expression for the fraction of exposed particles. In addition, the present study recognized the time dependence (i.e., a short-term vs. long-term regime) of the resuspension rate observed both experimentally (Wu et al., 1992; Wang et al., 2012) and by model predictions (Lazaridis and Drossinos, 1998; Friess and Yadigaroglu, 2001; Reeks and Hall, 2001) and confirmed the inverse dependence of the resuspension rate with time in long-term regime. Two regimes were also identified while evaluating the resuspension rate for a range of friction velocities, viz., a low-friction regime in which the resuspension rate increases with friction and a high-friction regime in which the opposite behaviour was observed.
Highlights
Particle resuspension from surfaces involves the physical process at which particles are detached from a surface and remain suspended into the ambient environment
Since particle resuspension is determined by the balance of forces that are required to entrain the particle to the ambient air and those that adhere the particles on the surface, an assessment of the interactions used in the present model becomes essential
A model based on a stochastic description of particle resuspension was used to evaluate single-layer resuspension rates from multilayer deposits for a range of exposure times and friction velocities
Summary
Particle resuspension from surfaces involves the physical process at which particles are detached from a surface and remain suspended into the ambient environment. Studies have shown that the distribution of particle size, statistical variation of the surface roughness and their impact to adhesive forces as well as material properties influence resuspension characteristics leading to a variety of experimental observations (Reeks and Hall, 2001; Ibrahim et al, 2003; Guingo and Minier, 2008; Goldasteh et al, 2013; Chatoutsidou et al, 2017) These observations give evidence that particle resuspension is a complex process where particle motion and its eventual entrainment to the ambient air is determined by statistical characteristics of the factors involved. Kinetics of a Multilayer Deposit Given a simplified deposit as the one shown, a kinetic to describe the time evolution of a multilayer deposit was originally given by Lazaridis and Drossinos (1998), followed subsequently by the kinetic proposed by Friess and Yadigaroglu (2001) Both kinetics use a set of coupled equations that describe the rate of change of the number of particles in layer i. Interaction Potential for a Particle-particle System The interaction energy between two identical spheres of radius Rp in contact is written (Lazaridis and Drossinos, 1998): VPP
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