Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA.
U.S. Environmental Protection Agency (EPA), Office of Research and Development, Research Triangle Park, Washington, DC, NC, USA.
J Expo Sci Environ Epidemiol. 2024 Mar;34(2):356-375. doi: 10.1038/s41370-023-00546-w. Epub 2023 Jun 20.
The COVID-19 pandemic was caused by the SARS-CoV-2 coronaviruses transmitted mainly through exposure to airborne respiratory droplets and aerosols carrying the virus.
To assess the transport and dispersion of respiratory aerosols containing the SARS-CoV-2 virus and other viruses in a small office space using a diffusion-based computational modeling approach.
A 3-D computational model was used to simulate the airflow inside the 70.2 m ventilated office. A novel diffusion model accounting for turbulence dispersion and gravitational sedimentation was utilized to predict droplet concentration transport and deposition. The numerical model was validated and used to investigate the influences of partition height and different ventilation rates on the concentration of respiratory aerosols of various sizes (1, 10, 20, and 50 µm) emitted by continuous speaking.
An increase in the hourly air change rate (ACH) from 2.0 to 5.6 decreased the 1 μm droplet concentration inside the office by a factor of 2.8 and in the breathing zone of the receptor occupant by a factor of 3.2. The concentration at the receptor breathing zone is estimated by the area-weighted average of a 1 m diameter circular disk, with its centroid at the center of the receptor mannequin mouth. While all aerosols were dispersed by airflow turbulence, the gravitational sedimentation significantly influenced the transport of larger aerosols in the room. The 1 and 10 μm aerosols remained suspended in the air and dispersed throughout the room. In contrast, the larger 20 and 50 μm aerosols deposited on the floor quickly due to the gravitational sedimentation. Increasing the partition between cubicles by 0.254 m (10") has little effect on the smaller aerosols and overall exposure.
This paper provides an efficient computational model for analyzing the concentration of different respiratory droplets and aerosols in an indoor environment. Thus, the approach could be used for assessing the influence of the spatial concentration variations on exposure for which the fully mixed model cannot be used.
COVID-19 大流行是由主要通过接触携带病毒的空气飞沫和气溶胶传播的 SARS-CoV-2 冠状病毒引起的。
使用基于扩散的计算建模方法评估含有 SARS-CoV-2 病毒和其他病毒的呼吸道飞沫在小办公空间中的传输和扩散。
使用三维计算模型模拟通风办公室内的气流。利用新型扩散模型，考虑湍流扩散和重力沉降，预测飞沫浓度的传输和沉积。数值模型进行了验证，并用于研究隔板高度和不同通风率对不同尺寸（1、10、20 和 50μm）连续说话时呼出的呼吸道气溶胶浓度的影响。
每小时空气交换率（ACH）从 2.0 增加到 5.6，使办公室内 1μm 液滴浓度降低了 2.8 倍，使受体人员呼吸区浓度降低了 3.2 倍。受体呼吸区的浓度由 1m 直径圆盘中的面积加权平均值估计，其质心位于受体人体模型的口中心。虽然所有的气溶胶都被气流湍流分散，但重力沉降对室内大颗粒气溶胶的传输有显著影响。1μm 和 10μm 的气溶胶仍悬浮在空气中，并在整个房间中扩散。相比之下，较大的 20μm 和 50μm 的气溶胶由于重力沉降很快沉积在地板上。将小隔间之间的隔板增加 0.254m（10 英寸）对较小的气溶胶和整体暴露影响不大。
本文提供了一种有效的计算模型，用于分析室内环境中不同呼吸道飞沫和气溶胶的浓度。因此，该方法可用于评估空间浓度变化对暴露的影响，而不能使用完全混合模型。
