Simulation of Droplet Dispersion from Coughing with Consideration of Face Mask Motion

Wearing a face mask is widely acknowledged as a critical defense against the transmission of the novel coronavirus (COVID-19) and influenza. This research focuses on the deformation of face masks during a cough and uses fluid dynamics simulations to more precisely predict the trajectory of virus-laden droplets. By employing motion capture technology, we measured the mask's displacement, which reaches up to 6 mm during a cough. Moreover, this paper delves into how the mask's deformation influences the movement of these droplets. We created a model for a small, spherical droplet and analyzed its dispersion by solving its motion equation, factoring in the cough's flow rate, droplet size distribution, and evaporation, all while considering the mask's deformation. Our findings reveal that mask deformation leads to a 7% reduction in average flow velocity compared to analyses using a non-deforming mask. Additionally, the distance droplets disperse increases over time when mask deformation is considered. As a practical application, we analyzed droplet dispersion in a scenario where a wheelchair is being pushed, utilizing airflow data that accounts for mask deformation. This analysis indicated that pushing a wheelchair at a speed of 0.5 m/s significantly raises the infection risk for individuals behind it.