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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口罩的流动物理学

尽管口罩用于防护空气传播的病原体和污染物已有一个多世纪的历史，但在过去两年应对 COVID-19 大流行期间，对其有效性的严格审查达到了顶峰。口罩的简单性掩盖了物理现象的复杂性，这些物理现象决定了其防御空气传播感染的有效性。这种复杂性源于这样一个事实：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、结构动力学、生理学甚至人类行为的相互作用的综合影响。然而，面罩的核心是一种流量处理装置，在当前的评论中，我们对面罩及其功能背后的关键现象采取了以流动物理为中心的观点。我们总结了实验测量的最新技术，以及不断增长的计算研究，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。