Respiratory droplet resuspension near surfaces: Modeling and analysis
Respiratory droplet resuspension near surfaces: Modeling and analysis
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DOI：
10.1063/5.0050447
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发表时间：
2021-07
影响因子：
3.2
通讯作者：
M. Nikfar;Ratul Paul;Khayrul Islam;M. Razizadeh;A. Jagota;Yaling Liu
中科院分区：
文献类型：
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作者：
M. Nikfar;Ratul Paul;Khayrul Islam;M. Razizadeh;A. Jagota;Yaling Liu
了解COVID-19的环境传播途径对于改善安全做法至关重要，特别是对更容易接触的卫生保健工作者而言。本文的重点是由于病毒载物飞沫从普通表面重悬浮而可能发生的二次传播，几项研究表明，在外部干扰下，这是可能的。这些干扰可能是行走、跑步时的身体运动、脱衣服或环境中的气流。本文利用一个三维两相模型，研究了呼吸液滴在不同表面上因突然搅拌引起的再悬浮动力学。实验研究了行走、手术手套脱下和物体掉落过程中的速度范围和变化。进行了参数化研究，以表征液滴尺寸和表面润湿性对从表面分离所需的最小初始液滴速度的影响。结果报告为在分离过程中的平均液滴速度，总分离时间和分离液滴体积。结果表明，在正常的日常活动中，大于200 μm的呼吸道飞沫可以从典型的表面上脱落。液滴与接触角≤90°的亲水表面部分分离，与接触角为> 90°的疏水表面全部分离。此外，引起重悬浮的最小初始液滴速度取决于液滴的大小。分离后的液滴速度是液滴大小、初始液滴速度和表面润湿性的函数。与小液滴相比，大液滴具有更大的分离体积百分比和更高的分离速度。最后，与疏水表面相比，将液滴从亲水表面分离需要更高的初始速度。结果表明，液滴引起分离的最小初始速度为2 m s−1，而我们的实验表明，在正常的人类活动中，表面速度可达3 m s−1。我们还建立了一个分析模型来预测从不同表面分离液滴所需的动能，该模型与数值结果吻合得很好。液滴分离的机理是由表面运动引起的液滴动能与由于液滴-表面相互作用以及液滴-蒸气和表面-蒸气相互作用而产生的表面能之间的竞争决定的。我们相信，这项基础研究的结果可以潜在地用于建议适当的表面润湿性和安全运动，以减少呼吸液滴从各种表面的再悬浮。
Knowing the environmental spreading pathway of COVID-19 is crucial for improving safety practices, particularly for health care workers who are more susceptible to exposure. This paper focuses on the possible secondary transmission due to resuspension of virus-laden droplets from common surfaces, which several studies have shown to be possible under external disturbances. Such disturbances could be body motion during walking, running, clothes removal, or airflow in the environment. In this paper, a three-dimensional two-phase model is utilized to study respiratory droplet resuspension dynamics on various surfaces due to sudden agitation. The velocity range and variation during walking, surgical glove removal, and dropping an object are studied experimentally. A parametric study is performed to characterize the effects of droplet size and surface wettability on the minimum initial droplet velocity required for detachment from surfaces. The results are reported as average droplet velocity during the detachment process, total detachment time, and detached droplet volume. The obtained results indicate that respiratory droplets larger than 200 μm can detach from typical surfaces due to normal daily activities. Droplets are partially separated from hydrophilic surfaces with contact angle ≤ 90 °, while the entire droplet is detached from hydrophobic surfaces with contact angle > 90 °. Furthermore, the minimum initial droplet velocity to induce the resuspension depends on the droplet size. Droplet velocity immediately after detachment is a function of droplet size, initial droplet velocity, and surface wettability. Bigger droplets have larger detached volume percentage as well as higher velocity after detachment compared to smaller droplets. Finally, a higher initial velocity is needed to separate droplets from hydrophilic surfaces as compared to hydrophobic surfaces. In accordance with the results, the droplet minimum initial velocity to cause detachment is 2 m s−1, while our experiments show that surface velocity can reach up to 3 m s−1 during normal human activities. We also develop an analytical model to predict the required kinetic energy to detach droplets from different surfaces, which is in good agreement with numerical results. The mechanism of droplet detachment is dictated by a competition between droplet kinetic energy induced by surface motion and surface energy due to droplet–surface interaction as well as droplet–vapor and surface–vapor interactions. We believe that the results of this fundamental study can potentially be used to suggest proper surface wettability and safe motion that reduce respiratory droplet resuspension from various surfaces.