R. Perić - Institute for Fluid Dynamics and Ship Theory, Hamburg University of Technology, Am Schwarzenberg-Campus ۴ (C), ۲۱۰۷۳ Hamburg, Germany
M. Perić - Institute of Ship Technology, Ocean Engineering and Transport Systems, Faculty of Engineering, University of Duisburg-Essen, Bismarckstraße ۶۹, ۴۷۰۵۷, Duisburg, Germany

The use of face masks for the general public has been suggested in literature as a means to decrease virus transmission during the global COVID-۱۹ pandemic. However, literature findings indicate that most mask designs do not provide reliable protection. This paper investigates the hypothesis that the impaired protection is mainly due to imperfect fitting of the masks, so that airflow, which contains virus-transporting droplets, can leak through gaps into or out of the mask. The fluid dynamics of face masks are investigated via analytical and numerical computations. The results demonstrate that the flow can be satisfactorily predicted by simplified analytical ۱D-flow models, by efficient ۲D-flow simulations and by ۳D-flow simulations. The present results show that already gap heights larger than ۰.۱mm can result in the mask not fulfilling FFP۲ or FFP۳ standards, and for gap heights of ca. ۱mm most of the airflow and droplets may pass through the gap. The implications of these findings are discussed and improvements to existing mask designs are suggested.

Airflow, Computational fluid dynamics, Filtering Face Piece (FFP) masks, Respirators, made masks, Self, Surgical masks, Virus transmission, COVID, ۱۹ virus