Particle detachment, resuspension and transport due to human walking in indoor environments

In this work, particles detachment, resuspension and transport due to indoor human walking were studied numerically and experimentally. The stepping motions of the foot, down and up, were modeled using a combination of two effective circular disks. The flow generated by the squeezing film at the shoe-floor interface was assumed to be laminar and the corresponding velocity field was evaluated. The flow outside of the foot was modeled based on a wall jet theory. The effects of adhesion force and surface roughness were included in the analysis. Models for particle detachment and resuspension were developed. The effects of particle-wall adhesion force and the hydrodynamic drag and lift forces were included in the particle detachment model. Spreading and dispersion of resuspended particle clouds was also evaluated. Particle deposition, turbulent diffusion and Brownian diffusion were also included in the particle transport model. Comparisons of the model predictions for particle concentration in the room and for particle resuspension rate with the obtained experimental data showed good agreements. The simulation results showed that shoe bottom roughness, foot size, walking velocity, background velocity as well as the foot stepping velocities, down and up, all affected particle resuspension rate from the floor as well as the corresponding particle concentrations in the indoor environment.