Estimation of Infectious Respiratory Droplets Spread and Size Distribution Evolution with CFD Simulations

With the development of new vaccines against the COVID-19, the reopening phase of public spaces such as schools, universities, restaurants, offices, among others, is a reality. However, there is a global concern that the number of cases may increase because of new virus variants and future pandemics. We employ unsteady Reynolds-Averaged Navier-Stokes (URANS) with the Euler-Lagrange approach to predicts the spread of the infectious saliva droplets contained on a single cough or sneeze. We fitted the discrete phase data from the CFD results with probability density functions (PDFs) to estimate the droplet size distribution as a function of time. The results indicate that the suggested social distancing protocol is not enough to avoid the transmission of COVID-19 since small saliva droplets (≤ 12μm) can travel in the streamwise direction up to 4 m when an infected person coughs, and more than 7 m when sneezes. The number of droplets in locations close to the respiratory system of a healthy person increases when the relative humidity of the room is low. The URANS simulations performed agree with previous experiments and LES simulations. Also, we developed particle-based CFD simulations for quasi-real-time predictions of the droplet spread.