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

预测在打喷嚏、咳嗽或讲话等呼气事件中产生的飞沫和气溶胶的扩散是了解传染病传播和制定有效对策以遏制疫情的关键一步。在工业界和学术界使用的现有开源和商业工具，预测液滴和气溶胶的分散，依赖于简单的模型，无法捕捉底层湍流物理的细节。在这个项目中，通过实验和计算相结合的方法，改进模型的发展取得了进展，可以很容易地通过直接实施到现有的工具。该项目还包括重要的教育和外联活动。研究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的沉浸式三维表示作为一种教育工具。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讲习班。这一合作实验和计算项目的总体目标是量化的基本流动物理，管理的运输和分散液滴在脉动呼气流。使用离体咳嗽模拟器和人体受试者实验结合直接数值模拟，我们将量化的作用，产生的脉动呼气流量，气溶胶分散和评估二次驱逐的渗透长度的流量相互作用。通过将时间分辨测速技术与经过广泛验证的流体-颗粒模拟方法相结合，这项工作将在揭示新的流体物理学方面取得突破，这些物理学与流体相互作用对液滴夹带和分散的影响有关。一些预期的成果包括：（1）一个广泛的数据库的实验测量和高分辨率的模拟;（2）一个健全的理论基础，模拟湍流分散两相流。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分散，这是理解病毒感染传播的关键一步。开发的方法将用于研究液滴充满呼气射流与流动障碍物（如面罩）的相互作用，并评估其有效性，以减轻冲击呼气流的分散。该奖项反映了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。

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.