呼出飞沫与飞沫核在人际间传播是呼吸道疾病传染的重要环节之一。已有文献对真实飞沫蒸发和飞沫核形成过程考虑不足，对人体微环境影响的研究不够细致。本项目从三个尺度出发探索病房内呼出飞沫人际间空气路径暴露过程，对医院疾病传染控制具有重要意义。首先将呼出飞沫(1-100微米)组分简化为含悬浮球状小颗粒的NaCl溶液, 并将现有飞沫蒸发二阶段数学模型发展为多阶段模型，以更准确预测咳嗽等呼出飞沫在干、湿空气中的蒸发和扩散。其次通过全尺度实验研究不同通风条件下单个躺卧暖体假人呼吸流和热羽流的特征 (0.1-1m)，以及两个暖体假人之间的飞沫传播；数值模拟研究病房环境中(1-10m)飞沫初始粒径、空气湿度、人体间距、通风设置、姿势、呼吸同步性等因素对两人或多人之间飞沫核暴露的影响。最后实验结合数值模拟研究不同通风条件下门的开关和人体走动对不同负压隔离病房之间以及同一六人病房中(1-10m)飞沫核传播的影响。

Interpersonal transport of expiratory droplets and droplet nuclei in indoor environments constitutes a prerequisite for the transmission of respiratory diseases. Existing studies of inter-personal expiratory droplet exposure do not sufficiently consider evaporation of realistic droplets and the detailed impact of body microenvironment. This study aims to reveal the physical process of interpersonal airborne transport of droplets and droplet nuclei involving three length scales which is important for improving strategies of infection control. ..First, the composition of expiratory droplets would be simplified to NaCl solution containing suspended spherical particles (0.001-0.1mm). Our existing droplet two-stage evaporation mathematical model would be further developed to multi-stage evaporation model in order to more correctly predict droplet evaporation and dispersion in a turbulent buoyant puff induced by coughing and other respiratory activities in dry and humid air. . .Second, a series of experiments will be conducted to understand the characteristics of human exhalation airflows and thermal plume of a lying person simulated by a breathing thermal manikin (0.1-1m), in a full-scale test room with different ventilation systems. Further experiments employing two breathing thermal manikins will be carried out to evaluate the interpersonal transport of the expiratory droplets and droplet nuclei in a full-scale test ward. Numerical simulations of droplet dispersion considering droplet evaporation and droplet nucleus sizes will be carried out to evaluate the impacts of the parameters of droplet initial size, air humidity, distance between bodies , ventilation conditions , body posture, synchronization of exhalation etc on interpersonal exposure in hospital environments (1-10m) with two or more people.. .Finally, full-scale experiments and numerical simulations will also be carried out to investigate how transient events of realistic human walking and door motions influence the airborne transmission of droplet nuclei between different negative-pressure isolation rooms and within one six-bed isolation room (1-10m) with different ventilation systems.