The impact of ambient humidity on the evaporation and dispersion of exhaled breathing droplets: A numerical investigation
The impact of ambient humidity on the evaporation and dispersion of exhaled breathing droplets: A numerical investigation
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环境湿度对呼出呼吸液滴蒸发和分散的影响：数值研究
DOI：
10.1016/j.jaerosci.2017.10.009
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发表时间：
2018-01-01
影响因子：
4.5
通讯作者：
Zheng, Xiaohong
中科院分区：
文献类型：
--
作者：
Ji, Yichen;Qian, Hua;Zheng, Xiaohong
采用计算流体动力学（CFD）方法研究了环境相对湿度（RH）和气流模式对感染者呼出飞沫蒸发和扩散的影响。采用离散相模型（discrete phase model，简称CFD）计算液滴和空气的两相流.该模型通过文献中的实验和仿真结果进行了验证。在不同的通风系统中，从感染器中呼出具有不同直径（在10 μ m和100 μ m之间每隔10 μ m）的纯水滴，即与不同RH（0、30%、60%和90%）混合和置换。模拟并比较了液滴的直径变化、空间分布和扩散距离。结果表明，由于湍流加速了液滴与空气之间的热质传递，混合通风条件下液滴的蒸发速度比置换通风条件下快。然而，无论通风系统如何，小液滴（例如10 μ m）的干燥时间都非常短。在置换系统或高相对湿度环境中，低的空气流速会降低中等尺寸液滴（如50 μ m）的蒸发速度，而加速大尺寸液滴（如200 μ m）的滴落。对于100 μ m的液滴，它们在低相对湿度下蒸发快，而在高相对湿度下存款快。大多数飞沫集中在人的嘴的+/- 0.5米内，然后变成飞沫核或落到地面上。该模型可为确定适宜的湿度控制方式以防止近距离传染病传播提供参考。
The impact of ambient relative humidity (RH) and airflow patterns on the evaporation and dispersion of infectious droplets exhaled from an infector was studied by the computational fluid dynamics (CFD) method. The DPM (discrete phase model) was employed to calculate the two phase flow, i.e. droplets and air. The model is validated by experimental and simulation results in literature. Pure water droplets with different diameters (every 10 mu m between 10 mu m and 100 mu m) are exhaled from an infector in different ventilation systems, i.e. mixing and displacement with different RHs (0, 30%, 60% and 90%). The diameter variation, spatial distribution and spreading distance of droplets are simulated and compared. Results showed that evaporation of droplets under mixing ventilation is quicker than it under displacement ventilation due to accelerated heat and mass transfer between droplets and air by turbulence. However, the dried out time for small droplets (e.g. 10 mu m) are extremely short, whatever the ventilation system is. Slow air velocity in displacement system or high RH environment may lower the evaporation speed of middle size droplets (e.g. 50 mu m) and accelerate the dropping of large size droplets (e.g. 200 mu m). For 100 mu m droplets, they evaporate fast with low RHs while deposit fast with high RHs. Most droplets concentrate within +/- 0.5 m of the person's mouth before they become droplet nuclei or fall onto the ground. This model may offer some suggestions in identifying favorable humidity-control ways to prevent the short-range infection transmission.