Extended Lifetime of Respiratory Droplets in a Turbulent Vapor Puff and Its Implications on Airborne Disease Transmission
Extended Lifetime of Respiratory Droplets in a Turbulent Vapor Puff and Its Implications on Airborne Disease Transmission
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DOI：
10.1103/physrevlett.126.034502
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发表时间：
2021-01-19
影响因子：
8.6
通讯作者：
Lohse, Detlef
中科院分区：
文献类型：
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作者：
Chong, Kai Leong;Ng, Chong Shen;Lohse, Detlef
为了量化不同环境相对湿度下呼吸水滴的去向，对一个典型的呼吸事件进行了直接的数值模拟。我们发现，在相对湿度为50%的情况下，由于小液滴(初始直径为10微米)在被排出的湿喷雾中被湍流涡卷扫，它们的寿命比Wells的经典图像延长了30倍以上。随着环境相对湿度的增加，小液滴的寿命进一步延长，当相对湿度为90%时，小液滴的寿命增加到150倍左右，这意味着呼吸液滴在1s内的平流范围超过2m。利用拉格朗日统计，我们证明了湍流湿呼吸喷雾吞噬了小液滴，导致它们的寿命增加了许多数量级，这意味着它们在呼吸事件期间可以被输送得比大液滴远得多。我们的发现为更大的参数研究提供了起点，并可能对制定优化通风和室内湿度控制的策略具有指导意义。这些战略对于缓解今秋和即将到来的冬季新冠肺炎大流行至关重要。
To quantify the fate of respiratory droplets under different ambient relative humidities, direct numerical simulations of a typical respiratory event are performed. We found that, because small droplets (with initial diameter of 10 mu m) are swept by turbulent eddies in the expelled humid puff, their lifetime gets extended by a factor of more than 30 times as compared to what is suggested by the classical picture by Wells, for 50% relative humidity. With increasing ambient relative humidity the extension of the lifetimes of the small droplets further increases and goes up to around 150 times for 90% relative humidity, implying more than 2 m advection range of the respiratory droplets within 1 sec. Employing Lagrangian statistics, we demonstrate that the turbulent humid respiratory puff engulfs the small droplets, leading to many orders of magnitude increase in their lifetimes, implying that they can be transported much further during the respiratory events than the large ones. Our findings provide the starting points for larger parameter studies and may be instructive for developing strategies on optimizing ventilation and indoor humidity control. Such strategies are key in mitigating the COVID-19 pandemic in the present autumn and upcoming winter.