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Micro-Mechanics of Dense Suspension Flow

Dr. Abhinendra Singh, University of Chicago

Prof. Safa Jamali, Northeastern University

Rheology and physics of dense particulate systems, such as granular matter and suspensions, have attracted many researchers from fluid mechanics, to soft condensed matter physicists and tribologists alike over the past number of years. These materials display several distinctive phenomena such as yielding, shear thinning, shear thickening, or jamming, owing to complex dynamics at the particle level, which in turn controls the macroscopic behavior of the material.  While the debate on a number of aspects of the physics of dense suspension remains open, a consensus has emerged that ultimately constraints to particle motion play the central role in the rheology of dense particulate systems. Thus, increasingly larger stresses are exhibited in response to an applied deformation rate. Such hindrance in different modes of relative particle motion-translation, rolling, and twisting-is governed by microscale interactions. These interactions occur at the nanoscale, the imposed background flow can lead to the emergence of mesoscale force chains that can organize as clusters or networks giving resistance to the externally applied deformation. Characterizing their fluctuations, and relaxations in a statistical mechanics framework helps a deeper understanding of the stress propagation, network rigidity in the suspension. For broad utilization of this understanding in the context of industrial applications, constitutive models hold the key for a predictive description of microscopic mechanisms, normal stresses, and the time- and rate-dependent rheology of dense suspensions. Ultimately, the real-world applications and systems of interest deviate from ideal cases where one mode of interaction or particle type and size can be studied in isolation. This session will aim at bringing theoreticians, experimentalists, and computationalists active in the field together and focus on bridging the gap between the three fields mentioned above aiming at developing constraint-based rheology and physics of dense particulate systems. To stimulate new ideas and collaborations in a field that has seen tremendous growth over the past few years, this session can be impactful by building a multiscale approach involving microscopic constraints leading to the mesoscale force network that eventually affects the macroscopic response. This will help the community gain a deeper general understanding of these particulate systems for the purpose of developing improved continuum models.