Numerical study of expiratory droplet dispersion using a new Eulerian modeling approach

The increasing incidence of airborne transmitted diseases indoors has prompted the attention of studying expiratory droplet dispersion and transport in built environments. Droplet dispersion in a room under the conventional well-mixed and displacement ventilation is simulated. In this work, a source (i.e. a patient) and a receptor (i.e the susceptible object) were located in a mechanical ventilated room. This study evaluated droplet dispersion and mixing under well-mixing and displacement ventilation scheme. Two droplet nuclei sizes, 0.01 and 10 μm, are selected as they represent very fine and coarse droplets. The flow field is modeled using k-ε RNG model. A new Eulerian drift-flux methodology is employed to model droplet phase. Under the conventional ventilation scheme, both fine and coarse droplets are homogeneously dispersed within approximately 50 s. Droplet nuclei exhibit distinctive dispersion behavior, particularly for low airflow microenvironment. After 210 s of droplet emission, gravitational settling influences the dispersion for 10 μm droplets, and concentration gradient can still be observed for displacement ventilation.