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 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.

Copyright 2012 American Association for Aerosol Research

Acknowledgments

This work has been sponsored by the US Environmental Protection Agency under contracts 3C-R310-NTEX and 4C-R138-NAEX. The first author is currently supported by WCU (World Class University) program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology R31-10049. Computer resources were provided by the High Performance Computing component of North Carolina State University's Information Technology Division (http://www.ncsu.edu/itd/hpc).

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.