Fundamental and Applied Problems in Granular Flows

颗粒流动的基本问题和应用问题本项目侧重于颗粒材料流动的三个方面：波动、工业筒仓中的流动和应力以及土壤液化的研究。各种问题将采用跨学科的方法来解决，包括分析、计算和实验。后两部分也将涉及工业和岩土专家的投入。下面是每个子项目的详细信息。子项目1，剪切颗粒材料的波动：最近的工作表明，对于中等规模的系统，力和某种程度上的速度波动可能非常大。该项目的实验部分将为中等规模的缓慢剪切系统提供这些波动的额外定量表征。此外，新的实验将建立一个库埃特类型，将探测更大的长度和时间尺度上的力波动。这些实验将整合到正在进行的工作中，通过晶格型模型模拟力波动，并使用新型混合分子动力学和有限元代码进行计算。子项目2，工业筒仓中的流动：与Jenike and Johanson， Inc.公司的工程师合作，该项目的联合项目负责人将分析与典型料斗形状相对应的空间区域中的流动。这种分析将基于库仑材料和临界状态土力学（CSSM）。研究的一些方面将包括CSSM和库仑模型之间的关系，激波和稀薄波解，料斗流的边值问题，以及这些解的稳定性。一个重要的应用是流量校正装置的设计。子项目3，土壤液化：这种现象对应于松散的饱和水土壤突然失去承载能力，可能导致大规模滑坡。真实世界的石油失效/液化将与G. Gudehus及其同事合作进行研究。该项目将结合实验、数学分析、计算机模拟和工业/岩土专业知识，以更好地了解颗粒材料的流动。该研究领域对涉及所有类型颗粒材料的技术过程具有相当重要的意义，包括但绝不限于化学加工工业，以及煤、矿石、粮食和药品的处理。上述过程的许多方面没有得到充分了解，在某些情况下导致巨大的经济损失。还在考虑的是岩土工程问题，如堤防的稳定性，以及地震条件下土壤的稳定性。该项目将涉及将现有的颗粒材料理论应用于诸如料斗流动和垃圾填埋场土壤稳定性等基本问题。将开发新的模型，以便考虑颗粒流动的一些重要方面，如力的波动。该实验室最近的实验表明，在现有模型中没有考虑到的波动可能非常强烈，并且很可能需要为涉及颗粒流动的工业设备提供安全可靠的设计标准。这些模型一方面将与实验数据紧密联系在一起，另一方面将成为相关技术问题的计算机解决方案的基础。

Fundamental and Applied Problems in Granular Flow Michael Shearer/David Schaeffer This project focuses on three aspects of the flow of granular materials: an investigation of fluctuations, flows and stresses in industrial silos, and liquefaction of soils. The various issues will be addressed using an interdisciplinary approach involving analysis, computation and experiment. The latter two parts will also involve input from industrial and geotechnical experts. Details of each subproject follow. Subproject 1, fluctuations in sheared granular materials: Recent work has shown that fluctuations of forces and to some extent velocities can be very large for moderate scale systems. The experimental part of this project will provide additional quantitative characterizations of these fluctuations for modest scale slowly sheared systems. In addition, new experiments will be constructed of a Couette type that will probe force fluctuations on larger length and time scales. These experiments will be integrated into ongoing work to model force fluctuations by lattice type models, and computations using novel hybrid molecular dynamics and finite element codes. Subproject 2, flow in industrial silos: In collaboration with engineers at the firm Jenike and Johanson, Inc. the co-PI's of this project will analyze flows in a spatial region that corresponds to the shape of a typical hopper. This analysis will be based both on Coulomb materials and on critical state soil mechanics (CSSM). Some of the aspects under study will include an investigation of the relationship between CSSM and Coulomb models, shock and rarefaction wave solutions, boundary value problems for hopper flow, and stability of such solutions. An important application is the design of flow corrective devices. Subproject 3, liquefaction of soils: This phenomenon corresponds to the abrupt loss of load-bearing capacity of a loose, water-saturated soil, possibly leading to a massive landslide. Real world s oil failure/liquefaction will be investigated in collaboration with G. Gudehus and his associates. This project will combine experiments, mathematical analysis, computer simulation and industrial/geotechnical expertise to better understand the flow of granular materials. The area of study is of considerable importance to technical processes involving all types of granular materials, including but by no means limited to chemical process industries, and to the handling of coal, ores, food grains, and pharmaceuticals. Many aspects of the above processes are not fully understood, leading in some cases to enormous financial losses. Also under consideration are geotechnical issues such as the stability of embankments, as well as the stability of soils under earthquake conditions. The project will involve the application of existing theories for granular materials to such fundamental problems as flows in hoppers and stability of soils in landfills. New models will be developed in order to take into account some important aspects of granular flows such as fluctuations of forces. Recent experiments in this lab have shown that fluctuations, which are not accounted for in existing models, can be very strong and may well be necessary to provide safe and reliable design criteria for industrial devices involving granular flows. The models will be tightly linked to the experimental data, on the one hand, and, on the other hand, will be the basis of computer solutions for relevant technical problems.