Numerical modeling of particles resuspension due to human stepping

In this paper, the induced airflow and the resultant resuspension of particles due to human walking are studied numerically using the dynamic mesh technique. Based on the results, the air is ejected from the sole and floor gap when the foot moves down, similar to a radial wall jet. During the upward motion, a strong gap flow is induced beneath the sole, which causes the surrounding air to be sucked toward the shoe center. Accordingly, particles are mainly detached in the downward motion of the foot. Then, they are entrained into the far-field flow during the foot's upward motion. Simulations indicate that the region beneath the sole edges is the most susceptible area for particles to be detached. As a result, fast walking is associated with a higher resuspension rate per footstep, up to two orders of magnitude due to increased shear stress on the floor. Although the shoe size influences the rate of particle resuspension, it is not as significant as the stepping time. Based on the results, the shear velocity due to stepping may be up to 0.4 m/s which can resuspend 10 μm particles with a resuspension rate of about 10-5 s-1. The effect of the main geometric features of the stepping process, including the stepping time and the shoe size, are investigated to provide a general correlation for its prediction with the R-squared value of 0.99.