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

Northwestern University, Evanston IL

Investigators

Abstract

CBET - 1511450 PI: Umbanhowar, Paul Granular 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.