Fluctuations and Flow for Granular Materials

点击翻译按钮获取中文摘要

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. ***