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Dynamics of granular raft on a moving interface: assembly, structure, and property

移动界面上颗粒筏的动力学：装配、结构和属性

基本信息

批准号：
2032354
负责人：
Sungyon Lee
金额：
$ 44.6万
依托单位：
University of Minnesota-Twin Cities
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-01-01 至 2024-12-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2032354&HistoricalAwards=false
关键词：
Dynamics granular raft moving interface

项目摘要

The “Cheerio’s effect” refers to the spontaneous aggregation of floating particles on the fluid-fluid interface through capillary interactions. The particles floating on the interface can form stable particle rafts with unique properties that have inspired technological innovations such as liquid marbles and bicontinuous gels. In addition, aggregates of large granular particles on water surfaces are commonly seen in the open environment, ranging from the assembly of mosquito eggs, shade balls to prevent evaporation of reservoirs, to sand particles deployed to clean oil spills. Particle rafts of environmental importance are naturally subject to perturbations due to flow, which can affect the collective dynamics and stability of the raft. Yet, the connections between the dynamics of fluid-fluid interfaces and particle assembly remains unclear. This project aims to address the issue by combing tabletop experiments with a theoretical investigation on the dynamics of granular rafts on moving interface. The results of the research will provide not only a fundamental understanding of the behavior of particle rafts in natural contexts, but also a new engineering tool to design and tailor macroscopic properties of particle assembly. The project will include an educational plan that emphasizes engagement of undergraduate students. The students and post-docs involved in the project will have outreach and networking opportunities with industrial partners though the industrial program at University of Minnesota. In addition, the visual nature of the research provides a good opportunity for integrating commonplace surface tension phenomena, such as “Cheerio’s effects”, in undergraduate fluid mechanics courses. The overall objective of this research is to gain fundamental understanding of particle rafts on a moving fluid-fluid interface, ranging from the assembly to macroscopic properties of the rafts. A particle raft is a monolayer of particles trapped at the interface between two fluids. As unique low-dimensional materials comprising discrete elements, particle rafts have a wide range of technical applications. However, the focus of the state of the art is on the particles themselves, while the fluid-fluid interface serves mostly as a passive site with a globally fixed geometry onto which particles can self-organize. Only limited studies have considered the dynamics of the rafts made of large granular particles, where gravity plays a dominant role. By combining experiments and theory, this project will directly address the role of the moving fluid-fluid interface in the assembly process and the mechanical properties of granular rafts. Experimentally, the PIs will investigate the influence of the moving interface on the structure of granular rafts and characterize the mechanical properties of resulting rafts via linear and nonlinear compression tests. In parallel to experiments, the PIs will develop a continuum model incorporating the intrinsic gravity-driven dynamics missing in the current theory of colloidal rafts. Together, the theoretical model and experimental measurements will provide a comprehensive physical understanding on the formation and the response of granular rafts under different interfacial perturbations.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.

“Cheerio效应”是指漂浮颗粒通过毛细管相互作用在流体-流体界面上的自发聚集。漂浮在界面上的颗粒可以形成稳定的颗粒筏，具有独特的特性，激发了技术创新，如液体大理石和双连续凝胶。此外，在开放环境中，水面上的大颗粒聚集体是常见的，从蚊子卵的聚集体、防止水库蒸发的遮阳球，到用于清理溢油的沙粒。具有环境重要性的颗粒筏自然会受到由于流动引起的扰动，这会影响筏的集体动力学和稳定性。然而，流体-流体界面的动力学和颗粒组装之间的联系仍然不清楚。本计画旨在结合桌上实验与理论研究探讨移动界面上颗粒筏之动力学。研究结果不仅将提供对自然环境中粒子筏行为的基本理解，而且还将提供一种新的工程工具来设计和定制粒子组装体的宏观特性。该项目将包括一个强调本科生参与的教育计划。参与该项目的学生和博士后将通过明尼苏达大学的工业项目与工业合作伙伴进行外联和建立联系的机会。此外，视觉性质的研究提供了一个很好的机会，整合常见的表面张力现象，如“Cheerio的影响”，在本科流体力学课程。本研究的总体目标是获得基本的了解，在一个移动的流体-流体界面上的颗粒筏，从组装到宏观性能的筏。颗粒筏是在两种流体之间的界面处捕获的单层颗粒。颗粒筏作为一种独特的低维离散单元材料，具有广泛的应用前景。然而，现有技术的重点是颗粒本身，而流体-流体界面主要用作具有全局固定几何形状的被动位点，颗粒可以在其上自组织。只有有限的研究考虑了由大颗粒组成的筏的动力学，其中重力起主导作用。本计画将以实验与理论相结合的方式，直接探讨流体-流体界面在颗粒筏组装过程中所扮演的角色，以及颗粒筏的力学特性。在实验上，PI将研究移动界面对颗粒筏结构的影响，并通过线性和非线性压缩试验表征所得筏的力学性能。在实验的同时，PI将开发一个连续体模型，该模型将结合当前胶体筏理论中缺少的内在重力驱动动力学。理论模型和实验测量将为不同界面扰动下颗粒筏的形成和响应提供全面的物理理解。该奖项反映了NSF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。