Modeling Size and Density Segregation in Dense Granular Flows

Event Date: September 14, 2023
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Rich Lueptow, Professor and Senior Associate Dean, McCormick School of Engineering, Northwestern University

Seminar: Thursday, September 14. 2023—1:30PM, POTR 234
Q&A Immediately following at 2:30 PM


Modeling Size and Density Segregation in Dense Granular Flows



In dense granular flows of particles differing in size, small particles fall between large particles to segregate in lower portions of the flow thereby displacing large particles upward, a process known as “percolation.” Similarly, light particles rise above heavy particles as they flow due to “buoyancy.” The resulting segregation due to percolation or buoyancy depends on the differences between the particles and flow conditions. We address granular segregation in two ways. The first approach is a continuum segregation model based on the advection-diffusion equation with a term added to account for particle segregation. This model can accurately predict mixing and segregation in both steady and transient flows for a variety of flow geometries and for a range of particle systems including multiple individual particle sizes, polydisperse (continuous) particle size distributions, mixtures of particles varying in both size and density, and non-spherical particles. The model can even be used to “design” combinations of particle size, density, and concentration that result in non-segregating particle mixtures. The second approach is to characterize the particle level segregation force via discrete element method simulations, which provides the ability to predict whether an intruder particle will rise or sink. These single intruder results have recently been extended to cooperative segregation phenomena in particle mixtures. Our current challenge is to connect segregation parameters in the continuum segregation model to particle level forces as well as to extend the segregation model to particle systems with a wide range of particle sizes. Funded by The Dow Chemical Company, the Procter & Gamble Company, and the National Science Foundation.


Richard M. Lueptow is Senior Associate Dean at the McCormick School of Engineering and Applied Science, Co-Founder of the Master of Product Design and Development Program, Professor of Mechanical Engineering and Chemical & Biological Engineering (courtesy), and former Charles Deering McCormick Professor of Teaching Excellence at Northwestern University. He received his BS in engineering (1978) from Michigan Technological University and his master’s degree (1980) and doctorate (1986) in mechanical engineering from the Massachusetts Institute of Technology. He has five years of product development experience in the biomedical industry and over three decades of academic experience on the faculty at Northwestern University. His research interests and expertise range from fundamental flow physics to water purification to pattern formation. His current research focuses on granular dynamics and membrane filtration. He has published over 180 journal papers, received numerous teaching and research awards, and is a Fellow of the American Institute of Chemical Engineers, the American Physical Society, and the American Society of Mechanical Engineers.