Collaborative Research: Effect of Pulsatility on Expiratory Droplet-Laden Flows

预测在打喷嚏、咳嗽或说话等呼气事件中产生的飞沫和气溶胶的扩散情况，是了解传染病传播和制定有效对策遏制疫情的关键一步。现有的用于工业和学术界的开源和商业工具，用于预测水滴和气溶胶的扩散，依赖于未能捕捉基本湍流物理细节的简单模型。在这个项目中，通过实验和计算相结合的方法，在开发改进的模型方面取得了进展，这些模型可以通过直接实施到现有工具中而很容易地被接受。该项目还包括重要的教育和外联活动。调查人员将扩大他们正在进行的努力，采用基于虚拟现实的成像，使充满液滴的呼气流动的身临其境的三维表示成为一种教育工具。这些教育工具将用于奥本大学和密歇根大学的外联活动和研讨会。这一合作实验和计算项目的总体目标是量化控制脉动呼气流中液滴传输和扩散的基本流动物理。使用体外咳嗽模拟器和人体实验，结合直接的数值模拟，我们将量化由脉动呼气气流产生的流动相互作用对气溶胶扩散的作用，并评估二次排气的穿透长度。通过将时间分辨测速仪与广泛验证的流体-颗粒模拟方法相结合，这项工作将在揭示与流动相互作用对液滴的携带和扩散的影响有关的新的流动物理方面取得突破性进展。一些预期的结果包括：(1)一个广泛的实验测量和高分辨率模拟的数据库；以及(2)一个用于模拟湍流弥散两相流的良好的理论基础。这种改进的流动物理量化和降阶模型的开发将能够更好地预测液滴扩散，这是了解病毒感染传播的关键一步。开发的方法将用于研究携带液滴的呼气射流与流动障碍(例如面罩)的相互作用，并评估其缓解撞击呼气气流扩散的有效性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Predicting the dispersion of droplets and aerosols generated during expiratory events like sneezing, coughing, or speech is a key step towards understanding the spread of infectious diseases and to develop effective countermeasures to contain outbreaks. Existing open-source and commercial tools used in industry and academia, to predict dispersion of droplets and aerosols, rely on simplistic models that fail to capture details of the underlying turbulent flow physics. In this project, through a combined experimental and computational approach, advancements are made towards the development of improved models that could be easily embraced through direct implementation into existing tools. This project also encompasses significant education and outreach activities. The investigators will expand their ongoing efforts to adopt Virtual Reality based imaging to enable immersive three-dimensional representations of droplet-laden expiratory flow as an educational tool. These educational tools will be used for outreach events and workshops at both Auburn University and the University of Michigan.The overall goal of this collaborative experimental and computational project is to quantify the fundamental flow physics that govern the transport and dispersion of droplets in a pulsatile expiratory flow. Using an ex-vivo cough simulator and human subject experiments combined with direct numerical simulations we will quantify the role of flow interactions, generated by pulsatile expiratory flow, on aerosol dispersion and assess the penetration length of secondary expulsions. By combining time-resolved velocimetry with an extensively validated fluid-particle simulation methodology, this effort will break ground in uncovering new flow physics relating the influence of flow interactions on the entrainment and dispersion of droplets. Some of the anticipated outcomes include: (1) an extensive database of experimental measurements and high-resolution simulations; and (2) a sound theoretical foundation for modeling turbulent disperse two-phase flows. Such improved quantification of flow physics and development of reduced-order models will enable better prediction of droplet dispersion, a key step towards understanding the spread of viral infections. The methods developed will be used to study the interaction of droplet-laden expiratory jets with flow barriers (for example face shields) and evaluate their efficacy to mitigate the dispersion of impinging expiratory flows.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.