Collaborative Research: Impact of a colloidal suspension droplet: Suspension flows at extreme shear rates

合作研究：胶体悬浮液液滴的影响：极端剪切速率下的悬浮液流动

• 批准号: 2004176
• 负责人: Michelle Driscoll
• 金额: $ 25.46万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2004176&HistoricalAwards=false
• 关键词: Collaborative; Research; Impact; colloidal; suspension

Non-technical Abstract:An impacting liquid drop is not only an eye-catching phenomenon, it is also an ideal testbed for studying material properties. This is due to the high speed at which an impacting drop spreads out (up to 10 m/s); this spreading process has been carefully studied in ordinary fluids, but little work has been done to understand how this impact behavior is modified in a complex fluid. Complex fluids such as ketchup, paint, and oobleck (cornstarch-in-water) have the property that their viscosity (resistance to flow) depends on the applied stress. Thus, these fluids flow quite differently depending on the stress they experience. This research project explores how this stress-dependent viscosity alters drop-impact behavior. Complex fluids are ubiquitous, and a deeper understanding of their behavior in impact processes is essential to industries such as food and drug processing, additive manufacturing, and printing/coating. In addition to the research synergy between PI Driscoll and Co-PI Cheng, the collaboration allows a unique opportunity for expanding students’ training: a personnel exchange has been implemented, so that the students involved in the project spend two weeks each year at their non-home institution. This personnel exchange provides trainees opportunities to connect with a larger network of scientists, as well as the experience of another discipline and institution. Additionally, the research team leverages the stunning and eye-catching phenomena of drop impact to design demos to educate the broader public about the fascinating properties of complex fluids. Technical Abstract:Liquid drop impact is a classic problem in fluid mechanics and soft materials and has been studied extensively for many decades. In comparison, studies focusing on the impact of non-Newtonian fluid droplets, particularly suspension droplets, have been few and far between, even though such processes are essential in industries such as food and drug processing, additive manufacturing, and printing/coating. This project addresses this knowledge gap by conducting an extensive study of impacting colloidal suspension droplets, providing a full understanding of the dynamics of suspension-drop impact and drawing a direct comparison between Newtonian and non-Newtonian drop impact processes. This systematic study varies control parameters such as suspension volume fraction, particle shape, impact energy, and target size. Using both advanced imaging techniques, as well as new tools to measure impact forces and stress distributions, the team aims to fully characterize both the kinematics and dynamics of impacting suspension droplets. Suspension-drop impact provides an ideal model system to probe suspension dynamics under complex and extreme conditions: a spreading droplet generates shear rates at least an order of magnitude higher than those that are accessible via standard rheometry. In addition, the isolated air-fluid interface in drop impact imposes a unique open boundary rarely seen in other circumstances. Thus, this project provides crucial missing information on suspension dynamics under extreme conditions, complementary to the current understanding of suspension flows obtained in conventional bulk rheological tests.This Division of Materials Research (DMR) grant supports research to study impacting colloidal suspension droplets between Newtonian and non-Newtonian drop impact processes with funding from the Condensed Matter Physics (CMP) Program in DMR of the Mathematical and Physical Sciences (MPS) Directorate.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.

非技术摘要：冲击液滴不仅是一种引人注目的现象，而且由于冲击液滴扩散的速度很高（高达 10 m/s），因此它也是研究材料特性的理想试验台。 ）；这种扩散过程已在普通流体中进行了仔细研究，但很少有人研究如何在复杂流体（例如番茄酱、油漆和欧不裂（水中的玉米淀粉））中改变这种冲击行为。具有其粘度（流动阻力）取决于所施加的应力的特性，因此，这些流体的流动取决于它们所经历的应力，该研究项目探讨了这种与应力相关的粘度如何改变复杂流体的跌落冲击行为。除了 PI Driscoll 和 Co-PI 之间的研究协同作用之外，更深入地了解它们在影响过程中的行为对于食品和药物加工、增材制造和印刷/涂层等行业也至关重要。 Cheng 表示，此次合作为扩大学生培训提供了独特的机会：已经实施了人员交流，因此参与该项目的学生每年在异地机构度过两周的时间。这种人员交流为学员提供了交流的机会。此外，研究团队还利用了更大的科学家网络以及其他学科和机构的经验来设计演示，以让更广泛的公众了解复杂流体的迷人特性。摘 要：液滴冲击是一个经典问题。流体力学和软材料的研究已经进行了数十年，相比之下，针对非牛顿流体液滴（特别是悬浮液滴）的影响的研究却很少，尽管此类过程在诸如此类的行业中至关重要。该项目通过对胶体悬浮液滴的冲击进行广泛研究，提供对悬浮液滴冲击动力学的全面了解，并在牛顿力学和牛顿力学之间进行直接比较，从而弥补了这一知识空白。非牛顿跌落冲击这项系统研究改变了控制参数，例如悬浮液体积分数、颗粒形状、冲击能量和目标尺寸，该团队旨在利用先进的成像技术以及测量冲击力和应力分布的新工具来充分表征这两个过程。悬浮液液滴撞击的运动学和动力学提供了一个理想的模型系统，可以在复杂和极端的条件下探测悬浮液动力学：扩散的液滴产生的剪切速率比通过标准流变测定法获得的剪切速率至少高一个数量级。此外，孤立的液滴中的空气-流体界面施加了在其他情况下罕见的独特开放边界的影响，因此，该项目提供了极端条件下悬浮液动力学的重要缺失信息，补充了当前在传统本体流变测试中获得的悬浮液流动的理解。材料研究 (DMR) 拨款支持在数学和物理科学 (MPS) DMR 凝聚态物理 (CMP) 项目的资助下研究牛顿和非牛顿液滴冲击过程之间胶体悬浮液滴的影响研究该奖项反映了 NSF 的法定使命，并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，被认为值得支持。

项目成果

Coexistence of solid and liquid phases in shear jammed colloidal drops

• DOI: 10.1038/s42005-022-00998-w
• 发表时间: 2022-09
• 期刊: Communications Physics
• 影响因子: 5.5
• 作者: P. Shah;S. Arora;M. Driscoll