Universal trends in human cough airflows at large distances
Universal trends in human cough airflows at large distances
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DOI：
10.1063/5.0021666
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发表时间：
2020-08-01
影响因子：
4.6
通讯作者：
Rao, Prasanna Simha Mohan
中科院分区：
文献类型：
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作者：
Simha, Padmanabha Prasanna;Rao, Prasanna Simha Mohan
咳嗽是流感和新冠肺炎(SARS-CoV-2)等疾病的主要传播途径之一。疾病传播是通过排出含有气雾滴的病原体而发生的。细小的液滴可以穿过口罩的层层，并被呼出的气流带走，而不像较大的液滴由于重力而沉淀下来。因此，定量评估佩戴和不佩戴不同类型口罩的典型咳嗽的最大旅行距离是很重要的。尽管近场数据可以在口附近获得，但远场数据却很稀缺。在这项研究中，使用了纹影方法，这是一种高度敏感的非侵入性流动可视化技术。它可以直接成像咳嗽产生的微弱密度梯度。通过对高速纹影图像的观察，对咳嗽时遮盖口腔的不同方法进行了评估。对肘部咳嗽的有效性进行了检验。对咳嗽的传播速度和有无口罩的传播距离进行了量化。研究还发现，无论使用不同类型的面具或测试对象，归一化距离-速度分布都会导致所有数据折叠到一条通用的无量纲曲线上。咳嗽流场的可视化和实验数据的分析表明，流动物理是由粘性涡环的传播所支配的。
Coughs are one of the primary means of transmission of diseases such as influenza and SARS-CoV-2 (COVID-19). Disease spreading occurs by the expulsion of pathogen containing aerosol droplets. Fine droplets can pass through layers of masks and are carried away by the exhaled airflow unlike larger droplets that settle down due to gravity. Hence, it is important to quantitatively assess the maximum distance of travel of typical human coughs with and without different types of masks. Even though near field data are available near the mouth, far field data are scarce. In this study, the schlieren method that is a highly sensitive, non-intrusive flow visualization technique is used. It can directly image weak density gradients produced by coughs. An assessment of different methods of covering the mouth while coughing is arrived at by using observations from high speed schlieren images. The effectiveness of coughing into the elbow is examined. The velocity of propagation of coughs and the distance of propagation with and without masks are quantified. It is also found that normalizing the distance-velocity profiles causes all the data to collapse onto a universal non-dimensional curve irrespective of the usage of different types of masks or test subjects. Visualization of cough flow fields and analysis of experimental data reveal that the flow physics is governed by the propagation of viscous vortex rings.