Career: Dynamics of coalescence and mixing during droplet impact on liquid films

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。许多重要的工业过程都涉及液滴对液体表面的冲击。示例包括喷墨打印、喷雾冷却、喷涂和内燃机中的燃油喷射。该奖项将使用先进的实验技术和分析方法，揭示从亚微米到毫米尺度的液滴与液体表面撞击的详细动力学。该项目的目标是确定环境条件和材料特性如何影响液滴撞击和撞击后的流体混合。该项目还将为学生参与和外展活动提供场地。高中生将通过加州大学圣地亚哥分校的ENLACE项目参与这项研究。本科生，尤其是第一代大学生，将参与由加州大学圣地亚哥分校火箭俱乐部赞助的外展活动。研究生将受益于一项新的实验，该实验基于该项目所探索的科学，该项目将为研究生课程开发。CAREER项目旨在研究液滴对液体表面的撞击，并为评估撞击动力学和混合行为提供关键见解。这项研究将涉及许多先进的光学测量，如成像、干涉测量、粒子图像测速和激光诱导荧光，所有这些都将在高速下进行。实验将确定与液滴和膜之间的界面气层的演化相关的微观物理，这控制了聚结过程。然后，该项目将重点研究聚结后液滴液体与膜的混合，以及碰撞惯性、膜几何形状、分子扩散和液体性质对混合的影响。这项研究的结果将有助于上述工业应用的设计，并将为其他多相过程提供更广泛的见解，包括在推进、发电、医疗、生物工程和制造应用中经常涉及的液滴-液滴和喷气-喷气相互作用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Many processes of industrial importance involve the impact of a liquid droplet on a liquid surface. Examples include inkjet printing, spray cooling, spray coating, and fuel injection in combustion engines. This CAREER award will use advanced experimental techniques and analytical methods to reveal the detailed dynamics of droplet impact with liquid surfaces from the sub-micron to millimeter scale. The goal of the project is to identify how ambient conditions and material properties influence droplet impact and fluid mixing following impact. The project will also provide venues for student engagement and outreach activities. High school students will participate in the research through UCSD’s ENLACE program. Undergraduates, especially first-generation college students, will be engaged in outreach activities sponsored by the UCSD rocket clubs. Graduate students will benefit from a new experiment based on the science explored in the project that will be developed for a graduate course.This CAREER project aims to investigate droplet impact on liquid surfaces and provide critical insights in assessing impact dynamics and mixing behavior. The study will involve many advanced optical measurements, such as imaging, interferometry, particle image velocimetry, and laser-induced fluorescence, all of which will be performed at high speed. Experiments will identify the microscopic physics associated with the evolution of an interfacial gas layer trapped between the droplet and the film, which controls the coalescence process. Then, the project will focus on the mixing of droplet liquid with the film immediately following coalescence and how mixing is affected by impact inertia, film geometry, molecular diffusion, and liquid properties. The results of the study will aid in the design of industrial applications mentioned above and will provide insight more broadly into other multiphase processes, including droplet-droplet and jet-jet interactions often relevant in propulsion, power generation, medical, bioengineering, and manufacturing applications.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.