Human induced flow field and resultant particle resuspension and transport during gait cycle

Abstract

Particle resuspension from flooring is believed to be an important source of particulate matter (PM) in the indoor environment. It is hypothesized that the high speed airflow generated between the flooring and the foot during the gait cycle is the main cause of particle resuspension. The simulation results show that particles are detached from the substrate during the downward motion of the foot. Furthermore, during the upward motion of the foot, additional particles may also be resuspended because of the suction flow generated by lifting the foot. These resuspended particles are then dispersed in the room by the airflow turbulence.In this study a combined experimental and computational studies were performed to shed light on the mechanisms of particle resuspension from flooring during the gait cycle. A mechanical foot experimental setup which mimics the human walking was developed and used to measure the rate of resuspension. In addition, to investigate the airflow field during walking, a three dimensional numerical model of a moving shoe during the gait cycle was generated using the ANSYS-FLUENT™ CFD package. A RANS approach with the RNG k-epsilon turbulence model was used for simulating the unsteady airflow field around and under the shoe. To include the shoe motion in the analysis, a user defined function (UDF) was developed and the dynamic mesh technique was used. A resuspension model was applied for the resuspension of pre-deposited particles from the flooring. The predicted particle resuspension were compared with the corresponding experimental results and good agreement was found.