Aerodynamic Particle Resuspension Due to Human Foot and Model Foot Motions

Human foot motions such as walking and foot tapping resuspend the particulate matter on the floor and redistribute it, increasing the particle concentration in air and affecting the indoor air quality. The objective of this article is to experimentally investigate the mechanism of particle resuspension and redistribution due to human foot motion from focusing on aerodynamic effect. In particular, we have examined generation and deformation of a vortex produced by foot motion and how it is affected by the shape of the shoe sole. The experimental methods used were particle visualizations and particle image velocimetry (PIV) measurements in air, supplemented by dye flow visualization in water. The flow visualizations with human foot tapping and stomping were performed to elucidate the particle resuspension in real situations. In the laboratory experiment, the foot was modeled as either an elongated plate or a prosthetic foot wearing a slipper, moving normal to the floor downward or upward. The particle resuspension and redistribution were associated with the wall jet between the foot and floor and the vortex dynamics. With the elongated plate foot model and the slipper, three-dimensional vortex structure strongly affected the particle redistribution and its direction.