Human-walking-induced wake flow - PIV experiments and CFD simulations

Quantitative measurement of indoor air distribution or local air velocity around a moving occupant is necessary to study the contaminant transport and energy efficiency in a building. This study measured the longitudinal and cross-sectional air flow distributions at different moving speeds. Experiments were conducted in a small-scale chamber with a moving cylinder, which served as a surrogate of a scaled-down human body. The flow field was measured by the particle image velocimetry technique. The measurements revealed an upward air vortex and a strong downward airflow behind the moving body along the vertical centreline. A vertical mixing and recirculation could be predicted, and such air movements would likely carry the contaminants on and near the floor upwards along the moving path. Symmetric downward and expansive vortices were also observed in the wake flow during the movement, from the top corners of the moving object to the floor. The disturbance range of the moving body was related to the moving speed, especially in consideration of the initial position of the vortex. The experimental results were used to validate a computational fluid dynamic model, which captured these fundamental flow features reasonably well. The large eddy simulation model yielded a higher accuracy than the Reynolds Average Navier-Stokes model in predicting the unsteady instantaneous flow in the entire domain.