Zeng Gang, Chen Lin, Yuan Haizhuan, Yamamoto Ayumi, Maruyama Shigenao
School of Mathematics and Computational Science, Xiangtan University, Xiangtan 411105, People's Republic of China.
National Institute of Technology, Hachinohe College, Hachinohe, Aomori 039-1192, Japan.
Phys Fluids (1994). 2021 Dec;33(12):123308. doi: 10.1063/5.0076572. Epub 2021 Dec 2.
The continuance of the COVID-19 pandemic largely depends on the spread of virus-carrying aerosols in ambient air. The mechanism of virus transmission and infection remains under intense investigation. In this study, an evaporation flow model of airborne sputum droplets is proposed which considers the evolution effects of the humidity field under different particle distributions and solid/salt fraction interactions. The incompressible Navier-Stokes equations characterize a stream of airflow jets, and the convection-diffusion-evaporation process is used to account for the inhomogeneous humidity field caused by the respiratory tract. Momentum equations for droplet dynamics which involve the effects of drag, gravity, and Brownian motion on sputum droplets are introduced to quantify the transport of droplets in a humidity field. The Lattice Boltzmann method is used to track the evolution of the aerosol in space and time under different ambient temperature and relative humidity conditions. The results of the simulation demonstrate that airborne humidity accelerates the evaporation rate of droplet, while supersaturated humid air forms a vapor mass in front of the respiratory tract. Despite the short lifespan of this phenomenon, it significantly hinders the evaporation of the droplets. Besides, the droplet vortex dynamics in a humidity field are sensitive to the droplet size.
新冠疫情的持续很大程度上取决于携带病毒的气溶胶在环境空气中的传播。病毒传播和感染的机制仍在深入研究中。在本研究中，提出了一种空气传播痰液飞沫的蒸发流模型，该模型考虑了不同颗粒分布和固/盐分数相互作用下湿度场的演变效应。不可压缩的纳维-斯托克斯方程描述了气流射流，对流-扩散-蒸发过程用于解释呼吸道引起的不均匀湿度场。引入了涉及阻力、重力和布朗运动对痰液飞沫影响的飞沫动力学动量方程，以量化飞沫在湿度场中的传输。格子玻尔兹曼方法用于跟踪不同环境温度和相对湿度条件下气溶胶在空间和时间上的演变。模拟结果表明，空气湿度加速了飞沫的蒸发速率，而过饱和潮湿空气在呼吸道前方形成蒸汽团。尽管这种现象持续时间很短，但它显著阻碍了飞沫的蒸发。此外，湿度场中的飞沫涡旋动力学对飞沫大小很敏感。
