Electrohydrodynamic interactions of drops

雷雨、喷墨打印、芯片实验室和原油破乳有什么共同之处？水滴和电场。电场使液滴以复杂的路径相互吸引、排斥或移动。对这些运动的控制对于利用电场操纵液滴的工艺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的液滴相互作用。将开发新的计算模型来模拟液滴在三维中的运动和流体流动，并解释重要的物理现象，如表面活性剂和沿液滴界面的电荷对流。研究成果将促进基础知识的发展，并对利用电场操纵液滴的各种技术产生影响。该项目涉及国际合作，将为将学生培养成参与全球事务的工程师提供机会。电场中液滴行为的视觉吸引力将被用于推广活动，以激发学生和普通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，如雷雨中雨滴的解体和许多应用，如喷墨打印、微流体、原油破乳和电喷雾。这些过程中有许多涉及液滴，长期以来，人们对了解液滴的电流体动力学感兴趣。虽然外加电场中的孤立液滴已经得到了广泛的研究，但许多液滴的行为在很大程度上还没有被探索。即使是成对的液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。在三个维度上，电流体相互作用可能是非常复杂和不平凡的。例如，在施加的均匀电场中，液滴最初可以沿场方向吸引并相互移动，但随后在横向方向分离，而不是沿场方向链接。为了了解潜在的机制，PI将进行理论和计算研究，并辅之以实验，系统地探索外加均匀电场中液滴对的动力学。首次研究了两个不同液滴在其中心线相对于外加磁场方向的任意间隔和取向下的动力学。将发展新的分析模型和使用边界积分方法的精确数值模拟来考虑电荷对流和表面活性物质的再分布。该项目结合了渐近理论、数值模拟和实验，这将导致对潜在流体动力学的更深入了解，以及发现与芯片上实验室等技术相关的新行为和工程机会。拟议的研究是跨学科的，整合了流体力学和应用数学领域的知识，并涉及国际合作。这将对与该项目相关的学生的教育和培训非常有益。电场中液滴行为的视觉吸引力将用于推广活动，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。

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.