CAREER: A continuum model for simultaneous prediction of granular flow and size-segregation in general geometries

CBET-1552556PI：Henann，David L.这个职业项目的目标是开发一个描述流动颗粒材料行为的理论模型。颗粒材料无处不在--它们包括沙子、土壤和雪等自然存在的材料，以及药丸和胶囊、粮食和催化剂颗粒等工农业材料。预测这些材料在流动过程中的行为提出了特殊的挑战，特别是当颗粒材料由不同大小的颗粒组成时。在这种情况下，流动会导致颗粒根据大小分离，这反过来又会影响整个材料的流动。在这个项目中开发的理论将使用非局部建模来描述由两个不同大小的颗粒组成的典型颗粒材料-称为双分散。所得到的模型将预测这种双分散体系在几种原型流动几何形状下的流动行为，并将结果与作为项目一部分进行的相应实验进行比较。还计划了各种教育活动，包括开发说明固体力学计算方法的新模块。该项目将招募本科生参与研究，并将举办研讨会以传播成果并吸引广泛的技术社区参与。基于非局部模型的预测连续体理论将同时预测由球形颗粒组成的双分散致密颗粒系统中的尺寸分离和流动。初步试验表明，这种方法产生的模型可以预测耦合的流场和分离模式。将进行一套系统的离散元计算，以分离剪切应变率驱动和重力驱动的分离机制，这将澄清流动和分离之间的双向耦合。然后使用连续介质热力学方法将该模型推广到三维流动，并开发非局部耦合理论的有限元实现。通过与典型流型下双分散颗粒系统的实验进行比较，验证了模型的预测。

CBET - 1552556PI: Henann, David L.The goal of this CAREER project is to develop a theoretical model that describes the behavior of flowing granular materials. Granular materials are ubiquitous - they include naturally-occurring materials such as sand, soil, and snow, as well as industrial and agricultural materials such as pharmaceutical pills and capsules, food grains, and catalyst particles. Predicting the behavior of these materials during flow poses special challenges, especially when the granular material consists of particles of different sizes. In this case, the flow causes the particles to segregate according to size, which, in turn, affects the flow of the material as a whole. The theory developed in this project will use nonlocal modeling to describe a representative granular material consisting of particles of two different sizes - called bidisperse. The resulting model will predict the flow behavior of this bidisperse system in several prototype flow geometries, and the results will be compared with corresponding experiments conducted as part of the project. A variety of educational activities are also planned, including the development of new modules illustrating computational methods in solid mechanics. The project will enlist undergraduates to participate in the research, and workshops will be conducted to disseminate results and engage broad technical communities. A predictive continuum theory, based on nonlocal modeling, will be developed that simultaneously predicts size segregation and flow in bidisperse dense granular systems composed of spherical particles. Preliminary tests have demonstrated that this approach produces a model that can predict coupled flow fields and segregation patterns. A systematic set of discrete-element calculations will be performed to isolate shear-strain-rate-driven and gravity-driven mechanisms of segregation, which will clarify the two-way coupling between flow and segregation. The model will then be generalized to three-dimensional flows using a continuum thermomechanics approach, and a finite-element implementation of the non-local, coupled theory will be developed. Predictions of the model will be validated by comparing with experiments of bidisperse granular systems in representative flow configurations.