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：宾夕法尼亚大学该项目的目标是为粒状材料如何响应外力而流动和变形提供基本指导。 该实验方法将利用内部开发的现代光学技术。 现代社会依赖于食品、种子、矿物、矿石、建筑材料、药丸和粉末等各种颗粒材料的运输、储存、混合、破碎和加工。 然而，实际应用效率低下，容易出现堵塞、错误包装和分层等灾难性故障。 该项目将通过建立微观颗粒尺度运动与施加力产生的宏观流动之间的基本联系，为改进工程实践奠定基础。 除了应用之外，这个主题也引起了人们的基本兴趣，因为粒状材料是已知物理世界边界上的非线性远离平衡系统，而且因为它们与地震、泥石流、侵蚀和荒漠化等地球物理问题有丰富的联系。 该项目将通过让研究生和本科生直接参与前沿科学研究，将现代物理学和测量技术带入研究生和本科生的教育经历中。 技术摘要：宾夕法尼亚大学该项目的目标是测量颗粒尺度动力学和与颗粒介质不寻常的宏观机械特性联系起来。 对于强强迫，微观动力学和宏观流动都是均匀的，并且可以通过流体动力学方法很好地描述。 然而，对于低强迫，响应可能在时间上是间歇性的并且在空间上是局部的。 这种异质性在干扰方法中加剧，并对建模和应用造成严重破坏。 该项目将使用高速视频显微镜以及内部开发的散斑可见光谱法来阐明颗粒尺度的行为。 这些探头将应用于堆流和料斗流、涉及冲击坑的流以及气体流化颗粒和棒。 结果将与整体流动行为和流变特性相关。 总而言之，这将建立基本的微观涨落机制，负责宏观尺度上注入能量的耗散，及其对变形和流动的影响。 该项目将把现代物理学和测量技术带入研究生和本科生的教育经历中，让他们直接参与尖端科学研究。