Multiphase Modelling and Experimental Characterization of Respiratory Microdroplet Suspension and Resuspension Dynamics Near Surfaces

COVID-19的主要传播途径是呼吸道飞沫和密切接触。了解COVID-19的环境传播途径对于改善安全实践至关重要。虽然在大的长度尺度上的呼吸液滴的流动物理学已经成为许多研究的焦点，但单个呼吸液滴在普通个人防护设备（PPE）表面上的悬浮行为的微尺度动力学以及由于这些液滴的再悬浮而引起的二次暴露风险尚未得到系统的评价。初步研究表明，环境条件，如湿度和温度以及表面性质，如表面化学，粗糙度和润湿性对气溶胶和液滴的演变机制有显着的影响。特别是，没有关于温度和湿度如何影响气溶胶的空气动力学和表面相互作用的全面研究。该项目的目标是通过结合计算建模和实验，提供对个体呼吸微滴和PPE表面在外部干扰（如身体运动）下相互作用的基本理解。这项研究将有助于探索医务人员和公众可以实践的潜在方法，以控制运动，湿度，温度和表面改性，从而减少气溶胶病毒的传播。该项目还将把研究纳入本科生和研究生的课堂教育，使液滴表面模拟工具提供给研究界，并推广到K-12和少数民族学生。该项目的目标是提供热-湿度-时间微滴动力学的基本理解和微滴表面相互作用的预测工具。建议工作的具体目标是：（一）开发一个三维多相计算模型，用于呼吸液滴在各种表面上的蒸发、传输、悬浮、粘附和再悬浮动力学;（ii）产生单个的载有模拟病毒的呼吸道微滴，其化学组成和大小与呼吸道微滴相似，并系统地研究在受控环境中这些液滴在不同表面附近的悬浮和再悬浮行为的动力学;及（iii）探讨温度、湿度、表面性质及外界干扰对液滴悬浮及再悬浮行为的影响，并提出减少病毒气溶胶传播的可行方法。综合的计算和实验方法将创造基于液滴的病毒传播和演变的湿度，温度和表面特性的函数的全面理解。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The main transmission routes for COVID-19 are respiratory droplets and close contact. Understanding environmental spreading pathways of COVID-19 is critical for improving safety practices. Although the flow physics of respiratory droplets at large length scales has been the focus of many studies, the microscale dynamics of the suspension behavior of individual respiratory droplets on common personal protective equipment (PPE) surfaces and the secondary exposure risk due to resuspension of those droplets have not been systematically evaluated. Initial studies show that environmental conditions such as humidity and temperature as well as surface properties, e.g. surface chemistry, roughness and wettability have significant effects on the evolution mechanism of aerosols and droplets. In particular, there is no comprehensive study on how temperature and humidity influence the aerodynamics and surface interaction of aerosols. The goal of this project is to provide fundamental understanding of the interaction between individual respiratory microdroplets and PPE surfaces under external disturbance such as body motion, through combined computational modeling and experiments. This research will help explore potential approaches that can be practiced by medical staff and general public to control motion, humidity, temperature, and surface modification that reduces aerosol-based virus spreading. The project will also incorporate research into education of undergraduate and graduate students in class, making a droplet-surface simulation tool to be made available to the research community, and outreach to K-12 and minority students.The goal of this project is to provide both a fundamental understanding of thermal-humidity-temporal microdroplet dynamics and a prediction tool for microdroplet surface interaction. The specific aims of the proposal work are to: (i) Develop a 3D multi-phase computational model for evaporation, transport, suspension, adhesion, and resuspension dynamics of respiratory droplet on various surfaces; (ii) Generate individual mimetic-virus laden respiratory microdroplets, with chemical composition and sizes similar to respiratory droplets, and investigate systematically the dynamics of the suspension and resuspension behavior of these droplets near various surfaces in a controlled environment; and (iii) Explore the effects of temperature, humidity, surface properties, and external disturbance on the suspension and resuspension behavior of droplets and suggest potential approaches for minimizing the aerosol spreading of virus. The integrated computational and experimental approach will create comprehensive understanding of the droplet-based virus transport and evolution as a function of humidity, temperature and surface characteristics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.