UNS: Controlling mixing and segregation of granular media using unsteady flows

颗粒状材料，如沙、雪和盐，是由大量的固体颗粒组成的，它们主要通过接触面相互作用。流动的粒状物质出现在自然现象中，如滑坡和雪崩，也出现在工业过程中，如制药业和矿石加工。当颗粒在大小、密度、粗糙度或其他物理特性上存在差异时，它们会在流动过程中分离，从而使加工复杂化并降低产品质量。该项目的目标是发现在非定常颗粒流（即随时间变化的流）中避免或减少离析和改善混合的方法。该项目包括实验，以确定流动调制如何最好地控制由不同大小的颗粒组成的材料的分离和混合。实验将辅以建模和计算机模拟，以帮助解释结果并预测控制偏析的最佳调制方法。结果将为工业从业者提供有用的处理方法和建模工具。项目团队将由不同的研究人员和学生组成，包括来自代表性不足的群体和当地高中的学生。该项目将研究非定常运动学和偏析之间的相互作用，以开发一个基于连续体的框架来预测有界堆流和旋转滚筒式流中多分散颗粒的空间偏析分布。研究结果将用于证明流动调节，如堆流中的进料速率变化或滚筒流中的转速变化，如何抑制离析并改善混合。该项目的研究结果将通过提供适用于广泛操作条件的方法来指导工业颗粒材料的工艺和系统，并由基于连续体的模型提供支持。该模型将考虑非定常流、偏析和碰撞扩散，所有这些都是广泛的颗粒过程中的重要元素。实验和模拟的结合将提供对颗粒系统中流动、分离、混合和模式形成的扩展和改进的理解。

CBET - 1511450PI: Umbanhowar, PaulGranular materials such as sand, snow, and salt consist of large numbers of solid particles that interact with each other primarily through contact foces. Flowing granular materials occur in natural phenomena, such as landslides and avalanches, and in industrial processes, such as pharmaceutical manufacturing and ore processing. When the particles differ from each other in size, density, roughness or some other physical characteristic, they can segregate during flow, which complicates processing and diminishes product quality. The goal of this project is to discover ways to avoid or reduce segregation and improve mixing in unsteady granular flows, i.e. flows that vary in time. The project involves experiments to determine how flow modulation can best control segregation and mixing for materials consisting of particles of various sizes. The experiments will be complemented by modeling and computer simulation that can help interpret the results and predict optimal modulation methods for controlling segregation. Results will generate useful processing methods and modeling tools for industrial practitioners. The project team will comprise a diverse group of researchers and students, including students from underrepresented groups and local high schools.The project will examine the interplay between unsteady kinematics and segregation to develop a continuum-based framework to predict spatial particle segregation distributions for polydisperse particles in bounded heap flow and rotating tumbler flow. The results will be used to demonstrate how flow modulations, such as feed rate variations in heap flow or rotational speed variations in tumbler flow, can inhibit segregation and improve mixing. Findings from the project will guide industrial granular materials processes and systems by providing methodologies that apply over a wide range of operating conditions and that are supported by a continuum-based model. The model will account for unsteady flow, segregation, and collisional diffusion, all of which are important elements in a broad array of granular processes. The combination of experiments and simulations will provide an expanded and improved understanding of flow, segregation, mixing and pattern formation in granular systems.