CAREER: Mesoscale Analysis of Dense Granular Flows

职业：密集颗粒流的中尺度分析

• 批准号: 1846991
• 负责人: Kerstin Nordstrom
• 金额: $ 61.53万
• 依托单位: Mount Holyoke College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-02-15 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1846991&HistoricalAwards=false
• 关键词: CAREER; Mesoscale; Analysis; Dense; Granular

Non-technical abstract: Granular materials like sands, grains, and powders are all around us, yet we still cannot predict precisely how they will flow or jam, unlike normal liquids. Both flow and jamming can create problems - clogging within a production line can be catastrophic, and flow from a rockslide can cause a state of emergency. Additionally many other systems are particulate in nature, such as cars and blood cells, and insights from the study of granular materials can give us insight into solving problems like traffic and blood clots. Part of the issue is that granular materials are difficult to image, and there is interesting physics happening at a wide range of time and length scales. This project will study the flow and jamming of granular materials with extremely fast video capture and high-definition resolution. The particles themselves are made of material that can appear to light up when they experience force. Thus the research team can not only detect the motion of every particle in the system, they can also measure the force on each individual particle. The acquisition and analysis of this data is critical for a more complete understanding of granular materials. The project is highly integrated with the broader educational goals of training future scientists and increasing science literacy in the public. Specifically, the principal investigator will provide training and mentorship to women undergraduate students involved in the research, and the project will support the training and mentorship of a postdoctoral researcher. The principal investigator will facilitate an immersive pre-college program for underrepresented groups interested in the physical sciences and engineering. Lastly, the principal investigator will continue to support and grow a monthly public science lecture series. Technical abstract: The overarching objective of this project is to advance the understanding of the dynamics of granular material flow and jamming with state-of-the-art time and spatial resolution, in addition to grain-scale force measurements. The long-term goal is to understand the structural and dynamical signatures at the mesoscale that control the clogging and flow of granular materials. The research team performs this work in the context of one particular flow geometry, though the methods are transferrable to other granular systems. In this system, the flowing state has been found to be described by the empirical Beverloo equation, but a sound theoretical footing for this behavior has not been established. Theoretical models of granular materials often use a continuum approach or a microscale "bottom-up" approach. However, it has become exceedingly clear that the behavior of granular materials depends on multiple length scales, and a functional predictive model must take various mesoscales into account. There has also been recent interest in the transition from flow to clogging in this system, and whether it is similar to (or different from) the jamming or glass transitions. This work will directly probe the nature of the clogging transition, and will contribute to forming better theoretical models of granular flow. The research team directly measures the microscopic particle motions, and mesoscale features such as the force network and rearranging clusters of particles, all with extremely high time and spatial resolution. The force network is measured by the use of photoelastic grains. In addition to experiments, the research team performs complementary molecular dynamics simulations for comparison. The data is analyzed for mesoscale features such as cooperative rearrangments, shear transformation zones, and particle segregation, and the initial packing structure of the system is modified as a control parameter. Network analysis techniques such as community detection algorithms are used to further analyze the evolution of the contact and force networks during flow and clogging events. In tandem, the research team is building a public library of collective motion metrics and documenting their use in disparate fields, with the goal of spawning more efficient implementation and cross-disciplinary collaborations.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：像沙子、颗粒和粉末这样的颗粒状物质在我们周围无处不在，但我们仍然不能准确地预测它们将如何流动或堵塞，不像正常的液体。流动和堵塞都会造成问题--生产线内的堵塞可能是灾难性的，而从岩石流中流出的水可能会导致紧急状态。此外，许多其他系统本质上是颗粒状的，如汽车和血细胞，研究颗粒状材料的见解可以让我们深入了解如何解决交通和血栓等问题。问题的一部分是，颗粒状物质很难想象，而且在广泛的时间和长度尺度上发生了有趣的物理现象。该项目将以极快的视频捕获和高清晰度分辨率研究颗粒状物质的流动和干扰。这些粒子本身是由材料组成的，当它们受力时，这些材料似乎会发光。因此，研究团队不仅可以检测系统中每个粒子的运动，还可以测量每个单独粒子所受的力。这些数据的获取和分析对于更完整地了解颗粒材料是至关重要的。该项目与培养未来科学家和提高公众科学素养的更广泛的教育目标高度结合。具体而言，首席研究人员将为参与研究的女本科生提供培训和指导，该项目将支持博士后研究人员的培训和指导。首席研究员将为对物理科学和工程感兴趣的代表不足的群体提供身临其境的大学前课程。最后，首席调查员将继续支持和发展每月一次的公共科学系列讲座。技术摘要：该项目的主要目标是促进对颗粒物质流动和干扰动力学的理解，以及最新的时间和空间分辨率，以及颗粒尺度的力测量。长期目标是了解控制颗粒物质堵塞和流动的中尺度结构和动力学特征。研究小组在一种特定流动几何的背景下进行这项工作，尽管这些方法可以转移到其他颗粒系统。在该体系中，流动状态可用经验Beverloo方程来描述，但这一行为的理论基础尚未建立。颗粒材料的理论模型通常使用连续体法或微尺度的“自下而上”法。然而，已经非常清楚的是，颗粒材料的行为取决于多个长度尺度，而功能预测模型必须考虑不同的中尺度。最近，人们还对该系统中从流动到堵塞的转变感兴趣，以及它是否类似于(或不同于)堵塞或玻璃转变。这项工作将直接探索堵塞转变的本质，并将有助于形成更好的颗粒流理论模型。研究小组直接测量微观粒子运动和中尺度特征，如力网络和重新排列的粒子簇，所有这些都具有极高的时间和空间分辨率。力网络是用光弹颗粒测量的。除了实验，研究小组还进行互补的分子动力学模拟以进行比较。分析了数据中的中尺度特征，如协同重排、剪切相变区和颗粒分离，并修改了系统的初始堆积结构作为控制参数。网络分析技术，如社区检测算法，被用来进一步分析流动和堵塞事件期间接触网络和力网络的演变。同时，研究团队正在建立集体运动度量的公共图书馆，并记录它们在不同领域的使用，目标是产生更有效的实施和跨学科合作。这一奖项反映了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。

项目成果

Mesoscale metrics on approach to the clogging point

接近堵塞点的中尺度指标

• DOI: 10.1007/s10035-021-01133-2
• 发表时间: 2021
• 期刊: Granular Matter
• 影响因子: 2.4
• 作者: Cai, Grace;Harada, Anna Belle;Nordstrom, Kerstin
• 通讯作者: Nordstrom, Kerstin

Silo flow and clogging in the presence of an obstacle

存在障碍物时筒仓流动和堵塞

• DOI: 10.1103/physrevfluids.7.054301
• 发表时间: 2022
• 期刊: Physical Review Fluids
• 影响因子: 2.7
• 作者: Harada, Anna Belle;Thackray, Emma;Nordstrom, Kerstin N.
• 通讯作者: Nordstrom, Kerstin N.