Respiratory droplet emissions and transport estimates using CFD for a nine-person, cubicle-style office
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Abstract: There has been strong evidence that the airflow patterns significantly affect the transmission of airborne infectious diseases in indoor environments (Li et al., 2007). Computational fluid dynamics (CFD) can be used to evaluate infectious droplet transport from source to receptor. For example, Bjorn and Nielsen (2002) and Topp et al. (2002) studied the dispersal of exhaled air and personal exposure in ventilated rooms using this approach. For this study, we used an improved CFD modeling approach to accurately predict airborne concentrations of virus-laded droplets from one infected individual in a representative nine-person, cubicle-style office environment. A transition three–equation k-kl-w turbulence model suitable for application to low Reynolds number flows developed by Walters and Cokljat (2008) was used in the simulations. A user-define-function (UDF) accounting for the turbulent diffusion of droplets and their gravitational sedimentation was developed and used to evaluate the infected droplet concentration in the office space. Instantaneously-mixed mass balance modeling, which assumes that the concentration is the same everywhere in the room, was also conducted for comparison. Assuming that one infected individual is present in the simulated workspace, we assess the concentration and exposure level at the other eight office workstations. Depending on which individual was “infected,” the concentrations in the room predicted by the CFD modeling varied widely, even for the steady-state condition. Scenarios that resulted in the largest differences in exposure estimates for the occupants in the room occurred when the infected person sat within a recirculation zone produced by the ventilation system. The impact of increasing the room ventilation rate and increasing the divider height above the top of the desk from 54” (1.37 m) to 64” (1.63 m) were also evaluated.