Numerical analysis of the efficiency of face masks for preventing droplet airborne infections

Abstract

In this study, the flow field around face masks was visualized and evaluated using computational fluid dynamics. The protective efficiency of face masks suppressing droplet infection owing to differences in the shape, medium, and doubling usage is predicted. Under the ongoing COVID-19 pandemic condition, many studies have been conducted to highlight that airborne transmission is the main transmission route. However, the virus infection prevention effect of face masks has not been sufficiently discussed, and thus remains as a controversial issue. Therefore, we aimed to provide a beneficial index for the society. The topology-free immersed boundary method, which is advantageous for complex shapes, was used to model the flow in the constriction area, including the contact surface between the face and mask. The jet formed from the oral cavity is guided to the outside through the surface of the mask and leaks from the gap between the face and mask.A Darcy-type model of porous media was used to model the flow resistance of masks. A random variable stochastic model was used to measure particle transmittance. We evaluated the differences in the amount of leakage and deposition of the droplets during exhalation and inhalation, depending on the differences in the conditions between the surgical and cloth masks owing to coughing and breathing. The obtained result could be attributed to the epidemiological measures adopted against both the reduction of the risk of infecting others by suppressing the exhalation, and the inhalation amounts. I. INTRODUCTIONUnder the ongoing COVID-19 pandemic conditions, it is becoming clear that the infection route by droplet dispersion plays a dominant role. Hydrodynamic considerations are significant in exploring the spread mechanism of COVID-19, and computational fluid dynamics (CFD) is expected to be utilized in all physical aspects of droplet transmission, from the formation of droplets to transportation by airflow 1 . However, the number of studies on the efficiency of face masks for droplet infection is insufficient. In addition, some numerical indicators for clarifying the effectiveness of wearing masks would be beneficial for the society, which is still a controversial issue.Many visualized study results on the personal protective equipment (PPE), particularly face masks, have been reported over the last year. Verma et al. 2 demonstrated the effect of face masks