Quantifying the effect of a mask on expiratory flows
Quantifying the effect of a mask on expiratory flows
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DOI：
10.1103/physrevfluids.6.110511
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发表时间：
2021-11-23
影响因子：
2.7
通讯作者：
Stone, Howard A.
中科院分区：
文献类型：
--
作者：
Bourrianne, Philippe;Xue, Nan;Stone, Howard A.
口罩被广泛用于减少传染病的传播。虽然它们的主要目的是过滤致病液滴，但口罩也代表了呼出和吸入气流的多孔屏障。在这项研究中，我们通过跟踪一个人通过口罩呼出的空气，使用红外成像和粒子图像测速法进行照明雾滴周围的主题，表征空气动力学效应的存在的面具。我们展示了口罩如何将呼出的气流限制在呼吸或说话的人面前几十厘米的范围内。此外，我们发现，普通外科口罩的组织具有低渗透性，这有效地将呼吸或说话过程中产生的呼气射流转化为准垂直浮力驱动的气流。因此，佩戴口罩除了提供过滤功能之外，还提供了对传染性物质的直接运输的强有力的缓解。通过比较人类受试者和模型实验的结果，我们提出了一个模型来合理化口罩如何改变空气流动，从而我们提供了定量的见解，是有用的疾病传播的描述。
Face masks are used widely to mitigate the spread of infectious diseases. While their main purpose is to filter pathogenic droplets, masks also represent a porous barrier to exhaled and inhaled air flow. In this study, we characterize the aerodynamic effect of the presence of a mask by tracking the air exhaled by a person through a mask, using both infrared imaging and particle image velocimetry performed on illuminated fog droplets surrounding a subject. We show how a mask confines the exhaled flows within tens of centimeters in front of a person breathing or speaking. In addition, we show that the tissue of common surgical face masks has a low permeability, which efficiently transforms the jetlike flows of exhalation produced during breathing or speaking into quasivertical buoyancy-driven flows. Therefore, wearing a mask offers a strong mitigation of direct transport of infectious material in addition to providing a filtering function. By comparing results on human subjects and model experiments, we propose a model to rationalize how a mask changes the air flow, and thus we provide quantitative insights that are useful for descriptions of disease transmission.