Large Eddy Simulation of Particle Re-suspension During a Footstep

Abstract

Re-suspension of particulate matter under human activity can have a significant impact on particle concentrations in indoor environments. The removal of surface-bound particulates as a person's foot contacts a substrate and the subsequent transport of such particulates through wake entrainment effects and through deposition is an important mechanism for particle dispersion. To study aspects of this event, we perform high-fidelity simulations of particle transport due to the heel-to-toe contact of a foot with a particle-laden carpet. For this purpose, an immersed boundary method is extended to account for particle transport, re-suspension, and deposition near the surface of the foot. Particle deposition is modeled as a combination of gravitational settling, Brownian diffusion, and convective impaction, while a dynamic re-suspension model is used to model particle re-suspension from the surfaces. We demonstrate the details of transient transport phenomena of re-suspended particles during a heel-to-toe foot motion event. The effects of the thickness of the carpet layer, the foot penetration depth into the carpet layer, the foot speed, and particle sizes on the mass re-suspended are investigated. Parametric studies show that a deeper foot penetration into a thinner carpet layer increases particle re-suspension and a faster foot motion also increases the re-suspension. Re-suspension Disclaimer: The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of the US Environmental Protection Agency.Address correspondence to Jack R. Edwards, Department of Mechanical and Aerospace Engineering, North Carolina State University, 1200 Hillsborough Street, Raleigh, NC 27695-7910, USA. E-mail: jredward@ncsu.edu rates increase as the particle size increases for particles in a size range of 1-20 µm. Predicted re-suspension rates are compared with those obtained in recent experiments.

CFD modelling of particle resuspension in a toroidal geometry resulting from airflows during a loss of vacuum accident (LOVA)

“…To take into account the transient configuration, it is necessary to discretize the timescale with a timestep At small enough for considering a constant shear velocity on each time step. This adaptation was proposed by Choi et al [22] in a study on the particle resuspension during a footstep. The mean value of the resuspension rate X(t) is thus calculated for the timestep At considered by the following expression:…”

Simulation of vertical concentration gradient of influenza viruses in dust resuspended by walking

“…We used resuspension rate coefficients that were experimentally determined by walking on a hard floor seeded with particles in a well‐mixed chamber (Qian and Ferro, ). The researchers measured resuspension rate coefficients for particles up to a maximum size of 10 μ m, and we linearly extrapolated these up to 50 μ m on the basis of results of large eddy simulation modeling of particle resuspension (Choi et al., ). We plotted resuspension rate coefficients versus particle size presented in Table 3 of Choi et al.…”

“…We plotted resuspension rate coefficients versus particle size presented in Table 3 of Choi et al. () and found them to be linearly increasing in the large‐particle regime. Figure shows the resulting resuspension rate coefficients as a function of particle size, where the four data points are from experimental measurements (Qian and Ferro, ).…”

“…Several other recent studies have also shown that indoor particle concentrations are increased by human activity (Alshitawi and Awbi, ; Hunt and Johnson, ; Ocak et al., ). These observations have inspired the development of models of particle resuspension that account for the various forces involved when a foot or shoe contacts the ground (Can et al., ; Choi et al., ; Zhang and Ahmadi, ; Zhang et al., ).…”

Experimental investigation of the airflow generated by the human foot tapping using the hot-wire anemometry

“…The aerodynamic disturbance generated by the impact of the foot on the ground during human walking is a phenomenon that has attracted much attention over the past several years. One of the most common applications of this phenomenon is in the human-walking-induced particle resuspension in indoor environments (Choi et al, 2012; Eisner and Wiener, 2010). It has been shown that particle resuspension from the flooring is a significant source of air pollution in indoor environments (Benabed et al, 2019b; Qian and Ferro, 2008; Thatcher and Layton, 1995).…”