Fluctuations and Flow for Granular Materials

9802602 Behringer这个凝聚态物理项目将主要通过实验来探索颗粒材料的动力学，但也需要一些理论和计算。它代表了三个区域。首先是波动在缓慢颗粒流中的作用。实验将提供包括二维和三维结构在内的静态和缓慢剪切粒子群的力波动和运动学特性的精确的局部和全局测量。其目标是对这些波动的长度和时间尺度提供定量衡量，并指导制定包括波动影响在内的模型。第二，以二元碰撞为特征的惯性区颗粒流的表征。实验将描述碰撞粒子的集体动力学，以及连续输入能量的系综的类热特性。最后，实验配置将探测细颗粒材料中的气体流动，以定量理解振荡颗粒材料的堆积效应。所有类型的颗粒流在商业上都是非常重要的，这个项目应该贡献与技术相关的知识，为学生和博士后提供基础和应用领域的优秀培训。这个凝聚态物理项目的重点是更好地理解颗粒物质的流动。这些材料无处不在，仅举几例，包括粮食、矿石、煤炭和药品。这些材料的加工对许多工业都是至关重要的，然而，对于如何描述这些材料还没有一个坚实的科学理解。因此，涉及颗粒处理的流程通常以设计效率的2/3运行，并且经常发生灾难性故障。该项目确定了三个研究领域，将提供更深入的科学理解，并具有应用于商业过程的潜力。对于缓慢流动的系统，我们将描述波动的性质，已知波动很大，因此具有潜在的破坏性，但描述得很差。对于快速搅拌/震动系统，实验将基于这些系统与气体的相似性来测试模型。最后，对于足够小的颗粒，如典型的沙子、裂化催化剂或粉末，周围的空气流动很重要。实验将描述颗粒与周围气体之间的相互作用。该项目还将为一至两名研究生提供技术职业培训，并为博士后研究人员和本科生提供培训。＊＊＊

9802602 Behringer This condensed matter physics project will probe the dynamics of granular materials primarily via experiments but with some theory and computation. Three areas are represented. First is the role of fluctuations in slow granular flows. Experiments will provide precise local and global measures of fluctuations in forces and in kinematic properties of static and slowly sheared ensembles of particles, including both two- and three-dimensional configurations. The goal is to provide a quantitative measure of the length and time scales for these fluctuations, and to guide the development of models that include the effects of fluctuations. Second is the characterization of granular flows in the inertial regime characterized by binary collisions. Experiments will characterize the collective dynamics of colliding particles, and the thermal-like properties of ensembles with a continuous input of energy. Finally, experimental configurations will probe gas flow in fine granular materials, with an eye to quantitatively understanding heaping effects for shaken granular materials. Granular flows of all types are highly important commercially, and this project is should contribute knowledge that is technically relevant, as provide excellent training for students and post-docs in both fundamental and applied areas. %%% This condensed matter physics project is focused on better understanding the flow of granular materials. Such materials are ubiquitous and include food grains, ore, coal, and pharmaceuticals, to name only a few. The processing of these materials is vital to many industries, yet, there is not a solid scientific understanding of how to describe these materials. As a consequence, processes involving granular processing typically operate at 2/3 of design efficiency, and catastrophic failures are frequent. This proje ct identifies three areas of study that will provide deeper scientific understanding with the potential for applications to commercial processes. For slowly flowing systems, we will characterize the nature of fluctuations, which are known to be large, and therefore potentially destructive, but are poorly characterized. For rapidly stirred/shaken systems, experiments will test models based on the similarity of these systems to a gas. Finally, for grains that are small enough, such as typical sand, cracking catalyst, or powder, ambient air flow is important. Experiments will characterize the interplay between grain and surrounding gas. This project will also provide technical career training for one to two graduate students as well as training for post- doctoral researchers and undergraduates. ***