Particle Resuspension in Turbulent Flow: A Stochastic Model for Individual Soil Grains

Abstract

A stochastic model for the motion of a particle initially at rest on a surface is explored. Fluid and adhesive forces are quantified based on first principles, and turbulent fluctuations are addressed probabilistically from probability distribution functions. A Monte Carlo process yields the distributions of particle position and velocity under a wide range of wind conditions and soil sizes. Results indicate that particle size and friction velocity are the most important factors in determining if a particle will resuspend and in predicting its subsequent motion. Larger wind speeds produce more violent fluctuations, which have a greater effect on small particles than on large particles. A theoretical analysis of the threshold friction velocity supports earlier experimental findings. The aerodynamic lift force cannot be neglected, and the torque exerted on a particle can be important in some cases. Applying the results of this work may contribute to reducing uncertainty in large-scale aerosol models.

High Resolution Study of Micrometer Particle Detachment on Different Surfaces

“…However, the rolling detachment is the dominant mechanism for particle removal in turbulent flows (Zhang and Ahmadi 2000;Ibrahim et al 2003). Despite the extensive studies of resuspension phenomena, there is still a significant lack of information about the path of particles very close to the surface (Harris and Davidson 2008). Further data are needed to provide insight in the micromechanics of the particle removal process (Zhang and Ahmadi 2000).…”

“…Despite extensive detachment studies, there is still a significant lack of information regarding the path of particles very close to the surface (Harris and Davidson 2008). Such information is needed to provide insight in the micromechanism of particle removal (Zhang and Ahmadi 2000).…”

A Monte Carlo Model for Soil Particle Resuspension Including Saltation and Turbulent Fluctuations

“…At time t o all particles are at rest. At time t o + t, wind entrains the particles most susceptible to resuspension following our earlier model of aerodynamic entrainment of a single particle (Harris and Davidson 2008). Based on kinetic energy analyses each particle is classified as suspended or saltating, and energy thresholds determine if saltating particles carry enough momentum to resuspend other bed particles.…”

“…Here we truncate the distribution so that particles cannot be launched from the surface in the negative z-direction. The horizontal component (standard deviation = 0.68 m s −1 , R 2 = 0.96) and vertical component (standard deviation = 0.04 m s −1 , R 2 = 0.90 and 0.99, respectively) of the initial particle velocity are (Harris and Davidson 2008):…”

“…From the force balance model described in Harris and Davidson (2008), particle velocities after liftoff are characterized by a Gaussian distribution in both the horizontal (x) and vertical (z) directions. Here we truncate the distribution so that particles cannot be launched from the surface in the negative z-direction.…”