Electrohydrodynamic interactions of drops

雷暴、喷墨打印、芯片实验室和原油破乳有什么共同之处？液滴和电场。电场使水滴在复杂的路径上相互吸引、排斥或移动。控制这些运动对于利用电场操纵液滴的技术过程的最佳性能至关重要，但对多液滴电流体动力学的了解有限。本项目将采用理论、模拟和实验相结合的方法来探索电场中水滴的相互作用。将开发新的计算模型来模拟液滴运动和流体的三维流动，并考虑沿液滴界面的表面活性剂和电荷对流等重要物理现象。该研究成果将推进基础知识，并影响利用电场操纵液滴的各种技术。该项目涉及国际合作，将为培养学生成为全球参与的工程师提供机会。液滴在电场中行为的视觉吸引力将被用于拓展活动，以激发学生和公众对流体动力学和工程的兴趣。流体和电场的相互作用是自然现象的核心，如雷暴中雨滴的分解，以及许多应用，如喷墨印刷、微流体、原油破乳和电喷雾。许多这些过程都涉及液滴，长期以来人们对液滴电流体动力学的理解一直很感兴趣。虽然一个孤立的液滴在外加电场中已被广泛研究，但许多液滴的行为在很大程度上尚未被探索。即使是成对的水滴相互作用也很少受到关注，现有的模型仅限于轴对称和二维几何。在三维空间中，电流体动力相互作用可以是非常复杂和非平凡的。例如，在施加均匀电场的情况下，液滴不是沿着电场方向连锁，而是在电场方向上相互吸引并相互移动，然后在横向上分离。为了理解潜在的机制，PI将进行理论和计算研究，并辅以实验，系统地探索施加均匀电场中的液滴对的动力学。本文首次研究了两种不同液滴在相对于外加场方向的任意分离和中心线取向下的动力学特性。新的分析模型和精确的数值模拟将使用边界积分法来解释电荷对流和表面活性剂的再分布。该项目整合了渐近理论、数值模拟和实验，这将使人们对潜在的流体动力学有更深入的了解，并发现与芯片实验室等技术相关的新行为和工程机会。本研究是跨学科的，整合了流体动力学和应用数学领域的知识，并涉及国际合作。这将对与项目相关的学生的教育和培训非常有益。液滴在电场中的行为在视觉上吸引人的性质将被用于外展活动，以激发学生和公众对流体动力学的兴趣。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。

What do thunderstorms, ink-jet printing, lab-on-a-chip, and crude oil demulsification have in common? Droplets and electric fields. An electric field causes drops to attract, repel, or move around each other in a complex path. Control over these motions is crucial for the optimal performance of the technological processes that use electric fields for droplet manipulation, yet knowledge of many-drop electrohydrodynamics is limited. This project will explore drop interactions in electric field using a combination of theory, simulations, and experiments. Novel computational models will be developed to model drop motions and fluid flow in three-dimensions and account for important physical phenomena such surfactant and charge convection along the droplet interface. The research outcomes will advance fundamental knowledge and impact the various technologies that utilize electric fields to manipulate droplets. The project involves international collaboration that will provide opportunities for training students as globally engaged engineers. The visually appealing nature of the droplet behavior in electric fields will be used in outreach activities to excite students and the general public about fluid dynamics and engineering.The interaction of fluids and electric fields is at the heart of natural phenomena such as disintegration of raindrops in thunderstorms and many applications such as ink-jet printing, microfluidics, crude oil demulsification, and electrosprays. Many of these processes involve droplets and there has been a long-standing interest in understanding drop electrohydrodynamics. While an isolated drop in applied electric fields has been extensively studied, the behavior of many drops is largely unexplored. Even the pair-wise drop interactions have received scant attention and existing models are limited to axisymmetric and two-dimensional geometries. In three dimensions, the electrohydrodynamic interactions can be quite complex and non-trivial. For example, in an applied uniform electric field, instead of chaining along the field direction, drops can initially attract in the direction of the field and move towards each other, but then separate in the transverse direction. To understand the underlying mechanisms, the PI will carry out a theoretical and computational study complemented with experiments that systematically explores the dynamics of a drop pair in an applied uniform electric field. For the first time, the dynamics of two dissimilar drops will be studied at arbitrary separation and orientation of their line-of-centers relative to the applied field direction. New analytical models and accurate numerical simulation using the Boundary Integral Method will be developed to account for charge convection and surfactant redistribution. The project integrates asymptotic theories, numerical simulations and experiments, which will lead to both a much deeper understanding of the underlying fluid dynamics as well as the discovery of new behaviors and engineering opportunities relevant to technologies such as lab-on-a-chip. The proposed research is interdisciplinary, integrating knowledge from the fields of fluid dynamics and applied math, and involves an international collaboration. This will be very beneficial for the education and training of the students associated with the project. The visually appealing nature of the droplet behavior in electric fields will be used in outreach activities to excite students and the general public about fluid dynamics.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.