Decay characteristics of expiratory aerosol in various diffuser-induced airflow patterns using large-eddy simulation

Abstract

This paper presents the decay characteristics of expiratory aerosol using large-eddy simulations coupled with Lagrangian particle tracking for evaluating the prevention of pathogen infection in a typical indoor environment. Ten cases of enclosed-rooms with five different diffuser-induced airflow patterns were investigated. For particles about 10 μm in diameter, which closely approximates the mean diameter of expiratory aerosol, the decay characteristics of each case with no obstacles proved that the most efficient case was the floor-supplied displacement type, followed by the ceiling-mounted line diffuser, floor-mounted diffuser, and ceiling-mounted square diffuser. The least effective case was the ceiling-mounted four-way cassette-type air diffuser under the same air changes per hour. However, in the situation of obstacles representing human bodies, the floor- supplied displacement type showed worse decay characteristics because of preventing the "piston flow-like" one-direction flow. On the other hand, the diffuser cases of the ceiling-mounted square type and the ceiling-mounted four-way cassette-type showed improved decay speed by exhaust and deposition. In particular, the ceiling-mounted square diffuser showed the most effective removal performance. These results imply that the flow configurations that induce small circulation caused by the inlet-outlet layout tend to improve the decay characteristics in terms of "the robust flow design" in a situation of complex flow field. © 2013 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.