Liu L, Wei J, Li Y, Ooi A
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.
Department of Mechanical Engineering, The University of Melbourne, Parkville, Melbourne, Vic., Australia.
Indoor Air. 2017 Jan;27(1):179-190. doi: 10.1111/ina.12297. Epub 2016 Mar 23.
Understanding how respiratory droplets become droplet nuclei and their dispersion is essential for understanding the mechanisms and control of disease transmission via droplet-borne and airborne routes. A theoretical model was developed to estimate the size of droplet nuclei and their dispersion as a function of the ambient humidity and droplet composition. The model-predicted dried droplet nuclei size was 32% of the original diameter, which agrees with the maximum residue size in the classic study by Duguid, 1946, Edinburg Med. J., 52, 335 and the validation experiment in this study, but is smaller than the 50% size predicted by Nicas et al., 2005, J. Occup. Environ. Hyg., 2, 143. The droplet nuclei size at a relative humidity of 90% (25°C) could be 30% larger than the size of the same droplet at a relative humidity of less than 67.3% (25°C). The trajectories of respiratory droplets in a cough jet are significantly affected by turbulence, which promotes the wide dispersion of droplets. We found that medium-sized droplets (e.g., 60 μm) are more influenced by humidity than are smaller and larger droplets, while large droplets (≥100 μm), whose travel is less influenced by humidity, quickly settle out of the jet.
了解呼吸道飞沫如何变成飞沫核及其扩散情况，对于理解通过飞沫传播和空气传播途径的疾病传播机制及控制方法至关重要。我们开发了一个理论模型，用于估算飞沫核的大小及其作为环境湿度和飞沫成分函数的扩散情况。该模型预测的干燥飞沫核大小为原始直径的32%，这与1946年杜吉德在《爱丁堡医学杂志》第52卷第335页发表的经典研究中的最大残留尺寸以及本研究中的验证实验结果相符，但小于2005年尼卡斯等人在《职业与环境卫生杂志》第2卷第143页预测的50%的尺寸。在相对湿度为90%（25°C）时的飞沫核大小可能比相对湿度小于67.3%（25°C）时同一飞沫的大小大30%。咳嗽喷射气流中呼吸道飞沫的轨迹受湍流的显著影响，湍流会促使飞沫广泛扩散。我们发现，中等大小的飞沫（如60μm）比更小和更大的飞沫受湿度影响更大，而大飞沫（≥100μm）的传播受湿度影响较小，会迅速从喷射气流中沉降下来。
