Experiments on Granular Fluctuation and Dissipation

颗粒涨落和耗散实验

• 批准号: 0704147
• 负责人: Douglas Durian
• 金额: $ 50万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-05-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0704147&HistoricalAwards=false
• 关键词: Experiments; Granular; Fluctuation; Dissipation

NON-TECHNICAL ABSTRACT: The goal of this project at the University of Pennsylvania is to provide fundamental guidance for how granular materials flow and deform in response to applied forces. The experimental approach will leverage modern optical technologies developed in-house. Modern society relies on transporting, storing, mixing, crushing, and processing such diverse granular materials as foods, seeds, minerals, ores, building materials, and pharmaceutical pills & powders. However, actual applications are inefficient and subject to such catastrophic failures as clogging, mispacking, and demixing. This project will lay the basis for improved engineering practices by establishing the fundamental link between microscopic grain-scale motion and the macroscopic flows that result from applied forces. Besides applications, this topic is of basic interest both because granular materials are nonlinear far-from equilibrium systems at the boundary of the world of known physics, and because of their rich connections to geophysical problems such as earthquakes, mudslides, erosion, and desertification. The project will bring modern physics and measurement techniques into the educational experience of graduate and undergraduate students by involving them directly in cutting-edge scientific research.TECHNICAL ABSTRACT: The goal of this project at the University of Pennsylvania is to measure grain-scale dynamics and to connect with the unusual macroscopic mechanical properties of granular media. For strong forcing, both the microscopic dynamics and the macroscopic flows are homogeneous, and are reasonably well described by hydrodynamic approaches. However, for low forcing, the response can be intermittent in time and localized in space. Such heterogeneities are exacerbated on approach to jamming, and create havoc both for modeling as well as for applications. This project will elucidate grain-scale behavior using high-speed video microscopy, as well as a multispeckle dynamic light scattering method developed in-house and known as Speckle-Visibility Spectroscopy. These probes will be applied to heap and hopper flows, to flows involving impact cratering, and to gas-fluidized grains and rods. The results will be correlated with bulk flow behavior and to rheological properties. Altogether this will establish the fundamental microscopic fluctuation mechanisms responsible for the dissipation of energy injected at the macroscopic scale, and their consequences for deformation and flow. The project will bring modern physics and measurement techniques into the educational experience of graduate and undergraduate students by involving them directly in cutting-edge scientific research.

非技术摘要：宾夕法尼亚大学的这个项目的目标是为颗粒材料如何流动和变形提供基本指导。 实验方法将利用内部开发的现代光学技术。 现代社会依赖于运输、储存、混合、破碎和加工各种颗粒状材料，如食物、种子、矿物、矿石、建筑材料和药物药丸粉末。 然而，实际的应用是低效的，并受到这样的灾难性故障堵塞，包装不当，分层。 该项目将通过建立微观颗粒尺度运动与由施加力引起的宏观流动之间的基本联系，为改进工程实践奠定基础。 除了应用，这个主题是基本的兴趣，因为粒状材料是非线性的远离平衡系统的边界上的已知物理学的世界，因为他们丰富的联系，如地震，泥石流，侵蚀和荒漠化的地球物理问题。 该项目将把现代物理学和测量技术引入研究生和本科生的教育经验，让他们直接参与前沿科学研究。技术摘要：宾夕法尼亚大学的这个项目的目标是测量颗粒尺度的动力学，并与颗粒介质的不寻常的宏观力学性质联系起来。 对于强强迫，微观动力学和宏观流动都是均匀的，并合理地很好地描述了流体动力学方法。 然而，对于低强迫，响应在时间上可以是间歇性的，在空间上是局部的。 这种异质性在接近干扰时加剧，并对建模和应用程序造成严重破坏。 该项目将使用高速视频显微镜以及内部开发的多斑点动态光散射方法（称为斑点可见度光谱学）来阐明颗粒尺度行为。 这些探头将被应用于堆和料斗流，涉及撞击坑流，以及气体流化颗粒和棒。 结果将与整体流动行为和流变性能相关。 总之，这将建立基本的微观波动机制，负责在宏观尺度上注入的能量的耗散，以及它们对变形和流动的影响。 该项目将把现代物理学和测量技术纳入研究生和本科生的教育经验，让他们直接参与尖端科学研究。