An Experimental and Numerical Study on Particle Resuspension from Human Activity

Epidemiological evidence has shown that the ambient airborne particle concentration is closely associated with cardio-pulmonary morbidity and mortality. Although these studies draw associations between human health and outdoor air, most personal exposure to particulate matter (PM) occurs indoors. Previous studies have found that human walking indoors results in a short-term, large elevation in particle concentration. Along with infiltration of outdoor air, cooking and smoking, resuspended particles from human activity is one of the primary indoor sources of PM.Particle detachment and resuspension from floors is a very complex progress which depends on micro-scale particle-surface interaction, as well as effects of macro-scale airflow. Although particle resuspension has been investigated via a number of experimental and modeling studies, estimated resuspension rates vary over several orders of magnitude and several important factors are not well understood. In particular, it is hypothesized that electrostatic charge built up during shoe-floor contact and separation may explain the difference between reported resuspension rates for different flooring materials. Also, models have shown that the shoe sole grooved/tread, which influences the airflow velocity in the vicinity of floor, will significantly affect the particle resuspension from the flooring. However, existing analytical models can only be applied for very simple geometry, i.e. circular disk. To understand and mitigate this source of human exposure, it is critical to bridge the knowledge gap.We propose to address the problem via experimental measurements combined with numerical modeling. A mechanical stepping device will be used firstly to determine the effects of different properties of shoes and floorings on the particle resuspension. Electrostatic properties and airflow around grooved shoes as well as the resulting size- resolved particle concentrations will be measured.For the numerical work, an in-house large eddy simulation (LES) based lattice Boltzmann (LB) model with a better capacity to model moving object through immersed boundary (IB) method will be developed and applied to this problem. The models will be verified by experimental data. Our preliminary work indicates that the LB/LES/IB method is a promising approach for this application and will provide the resolution needed to address the research questions.The PI and Co-I are uniquely qualified to conduct the proposed work. The related work they have accomplished and resources available will leverage the project substantially. The results of this study may be used for indoor exposure assessment as well as by other indoor air quality tools.