Sen Nirvik, Singh K K
Chemical Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
Phys Fluids (1994). 2021 Apr;33(4):045128. doi: 10.1063/5.0045289. Epub 2021 Apr 28.
As ongoing Corona virus disease 2019 pandemic is ravaging the world, more and more people are following social distancing norms, avoiding unnecessary outings and preferring online shopping from the safety of their home over visiting brick and mortar stores and neighborhood shops. Although this has led to a significant reduction in chances of exposure, human-to-human interaction at the doorstep of the customer might be involved during the delivery of the ordered items. This human-to-human doorstep interaction arises in some other situations also. There is a finite probability that the person standing in front of the door coughs or sneezes during such an interaction. In this work, a three dimensional (3D) Euler-Lagrangian computational fluid dynamic model is used to understand the transmission and evaporation of micrometer-size droplets generated due to a coughing event in this setting. Different possible scenarios varying in wind direction, wind velocity, ventilation in the vicinity of door, and extent of door opening have been postulated and simulated. The results obtained from numerical simulations show that in the presence of wind, the dynamics of transmission of droplets is much faster than the dynamics of their evaporation. Thus wind velocity and direction have a significant impact on the fate of the droplets. The simulation results show that even if the door is opened by a very small degree, cough droplets enter through the door. Having open windows in the vicinity of the door on a windy day is expected to reduce the chance of the exposure significantly.
随着2019年冠状病毒病大流行肆虐全球，越来越多的人遵循社交距离规范，避免不必要的外出，相较于前往实体商店和社区商店，更倾向于在家中安全地进行网购。尽管这已大幅降低了接触风险，但在交付订购商品时，可能会涉及顾客家门口的人际互动。这种人际家门口互动在其他一些情况下也会出现。在此类互动过程中，站在门前的人咳嗽或打喷嚏存在一定概率。在这项工作中，使用三维（3D）欧拉-拉格朗日计算流体动力学模型来理解在此场景下咳嗽事件产生的微米级液滴的传播和蒸发。假设并模拟了风向、风速、门附近的通风情况以及门打开程度不同的各种可能场景。数值模拟结果表明，在有风的情况下，液滴的传播动态比其蒸发动态快得多。因此，风速和风向对液滴的命运有重大影响。模拟结果表明，即使门只打开很小的角度，咳嗽飞沫也会通过门进入。在有风的日子里，在门附近打开窗户有望显著降低接触风险。
