Although face masks have been used for over a century to provide protection against airborne pathogens and pollutants, close scrutiny of their effectiveness has peaked in the past two years in response to the COVID-19 pandemic. The simplicity of face masks belies the complexity of the physical phenomena that determine their effectiveness as a defense against airborne infections. This complexity is rooted in the fact that the effectiveness of face masks depends on the combined effects of respiratory aerodynamics, filtration flow physics, droplet dynamics and their interactions with porous materials, structural dynamics, physiology, and even human behavior. At its core, however, the face mask is a flow-handling device, and in the current review, we take a flow physics–centric view of face masks and the key phenomena that underlie their function. We summarize the state of the art in experimental measurements, as well as the growing body of computational studies that have contributed to our understanding of the factors that determine the effectiveness of face masks. The review also lays out some of the important open questions and technical challenges associated with the effectiveness of face masks.

中文翻译：

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面罩的流动物理学


尽管口罩已经被用于防止空气中的病原体和污染物一个多世纪，但在过去两年中，为了应对 COVID-19 大流行，对其有效性的密切审查已达到顶峰。口罩的简单性掩盖了物理现象的复杂性，这些现象决定了它们作为空气传播感染的防御效果。这种复杂性植根于这样一个事实，即口罩的有效性取决于呼吸空气动力学、过滤流物理学、液滴动力学及其与多孔材料的相互作用、结构动力学、生理学甚至人类行为的综合影响。然而，面罩的核心是一种流动处理装置，在当前的评论中，我们以流动物理学为中心的视角来看待面罩及其功能背后的关键现象。我们总结了实验测量的最新技术，以及越来越多的计算研究，这些研究有助于我们理解决定口罩有效性的因素。该审查还列出了与口罩有效性相关的一些重要的悬而未决的问题和技术挑战。