Dynamics of Slow Granular Flow

慢速颗粒流动力学

• 批准号: 0070329
• 负责人: Douglas Durian
• 金额: $ 37.5万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-04-15 至 2003-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0070329&HistoricalAwards=false
• 关键词: Dynamics; Slow; Granular; Flow

This experimental condensed matter physics project will investigate the dynamics of granular flows that exhibit on/off intermittency. Such behavior is very common, but traditional measurement techniques do not have sufficient resolution and dynamic range to capture the very rapid grain-grain collisions and the slow on/off switching of the flows. A new approach will be employed in which this information is extracted from the second- and fourth-order intensity correlation functions for temporal fluctuations in the intensity of light multiply-scattered by the sample. Data will be obtained for intermittent surface flows (avalanches), Couette flows (stick-slip), and vibrated flows (periodic). Particular interest is in the crossover between smooth and intermittent flows as a function of forcing rate. This should aid in testing and developing theories, which are currently limited to either quasi-static or fully-fluidized regimes. This should be useful in a wide variety of industries, where transport and processing of granular materials is now accomplished only with great inefficiency. Insight may also be gained into closely related geophysical events such as landslides, erosion, and earthquakes. The project provides excellent training for graduate students in state-of-the art experimental methods and for introducing them to materials and topics at the forefront of modern condensed matter physics.%%%This experimental condensed matter physics project investigates the microscopic dynamics of granular flows that are slow and, hence, intermittent. Such behavior is familiar to anyone who has slowly poured a small amount of sand from a bucket, or rice from a bag, or tried to shake out one pill from a bottle. These flows are all smooth, like a liquid, only if very fast; if slow, they are intermittent via a series of avalanches. This behavior is important in a wide variety of industries, where foods, pharmaceutical and ceramic powders, building materials, raw ores, etc. need to be -but are often not- processed and transported efficiently without jamming. This behavior is also important in geophysical events such as landslides, erosion, and earthquakes. In spite of their ubiquity and importance, slow flows and the crossover to smooth fast flows are not yet understood. Current engineering theories are applicable only to smooth flows, and current physics theories are applicable only to very infrequent flows; none can capture the full range of behavior. The usual experimental methods are also incapable of simultaneously capturing the rapid grain motion during flow along with the slow on-off switching of the flow itself. This project will do so, for the first time, by state-of-the-art techniques involving photon correlations from laser light bounced off a sample. In addition to practical impact on industry and geophysics, this project will provide excellent training for students in new experimental methods and will introduce them to materials and topics at the forefront of modern condensed matter physics.

该实验性凝结物理项目将研究表现出内向内/关闭间歇性的颗粒流动的动力学。这种行为非常普遍，但是传统的测量技术没有足够的分辨率和动态范围来捕获非常快速的晶粒胶碰撞和流量的缓慢开/关。将采用一种新方法，其中将从第二阶和四阶强度相关函数中提取此信息，以在光线强度与样品散落的光强度下进行时间波动。将获得间歇性表面流（雪崩），couette流（粘粘）和振动流（周期性）的数据。特别感兴趣的是平滑和间歇流之间的交叉作为强迫率的函数。这将有助于测试和发展理论，这些理论目前仅限于准静态或完全荧光的制度。这应该在各种各样的行业中很有用，在这些行业中，颗粒材料的运输和加工现在只有效率低下才能完成。洞察力也可能获得密切相关的地球物理事件，例如滑坡，侵蚀和地震。该项目为研究生提供了出色的培训，以最先进的实验方法，并将其引入现代冷凝物理物理学的最前沿的材料和主题。%% %%这个实验性凝结物理学项目研究了慢慢且因此间隔间隔的粒状流动的微观动力学。任何慢慢从水桶或袋子里撒上少量沙子的人都熟悉这种行为，或者试图从瓶子里摇一丸。这些流都像液体一样光滑，只有在很快的情况下；如果缓慢，它们会通过一系列雪崩而间歇性。这种行为在各种各样的行业中都很重要，那里的食品，药品和陶瓷粉，建筑材料，原矿石等都需要 - 但通常不加工和运输而不会堵塞。这种行为在地球物理事件中也很重要，例如滑坡，侵蚀和地震。尽管它们的无处不在和重要性，但尚未了解慢速流动和平滑流动流的跨界。当前的工程理论仅适用于平滑流动，并且当前的物理理论仅适用于很少流动；没有人可以捕获全部行为。通常的实验方法也无法同时捕获流动过程中的快速晶粒运动，而流动本身的较慢开关切换。该项目将首次通过涉及激光光的光子相关性的最新技术来实现。除了对行业和地球物理的实际影响外，该项目还将为学生提供新的实验方法的学生提供出色的培训，并将其介绍给现代冷凝物理物理学的最前沿的材料和主题。