Wang Hongping, Li Zhaobin, Zhang Xinlei, Zhu Lixing, Liu Yi, Wang Shizhao
Phys Fluids (1994). 2020 Dec 1;32(12):125102. doi: 10.1063/5.0033849.
Coronavirus disease 2019 has become a global pandemic infectious respiratory disease with high mortality and infectiousness. This paper investigates respiratory droplet transmission, which is critical to understanding, modeling, and controlling epidemics. In the present work, we implemented flow visualization, particle image velocimetry, and particle shadow tracking velocimetry to measure the velocity of the airflow and droplets involved in coughing and then constructed a physical model considering the evaporation effect to predict the motion of droplets under different weather conditions. The experimental results indicate that the convection velocity of cough airflow presents the relationship with time; hence, the distance from the cougher increases by in the range of our measurement domain. Substituting these experimental results into the physical model reveals that small droplets (initial diameter ≤ 100 m) evaporate to droplet nuclei and that large droplets with ≥ 500 m and an initial velocity ≥ 5 m/s travel more than 2 m. Winter conditions of low temperature and high relative humidity can cause more droplets to settle to the ground, which may be a possible driver of a second pandemic wave in the autumn and winter seasons.
2019冠状病毒病已成为一种具有高死亡率和传染性的全球大流行传染性呼吸道疾病。本文研究呼吸道飞沫传播，这对于理解、建模和控制疫情至关重要。在当前工作中，我们实施了流动可视化、粒子图像测速和粒子阴影跟踪测速来测量咳嗽过程中气流和飞沫的速度，然后构建了一个考虑蒸发效应的物理模型，以预测不同天气条件下飞沫的运动。实验结果表明，咳嗽气流的对流速度与时间呈现一定关系；因此，在我们的测量范围内，咳嗽者与飞沫的距离增加了 。将这些实验结果代入物理模型表明，小飞沫（初始直径≤100μm）蒸发为飞沫核，而直径≥500μm且初始速度≥5m/s的大飞沫传播距离超过2m。低温和高相对湿度的冬季条件会导致更多飞沫沉降到地面，这可能是秋冬季节第二波疫情的一个潜在驱动因素。
