Soft Matter Seminar: Coherent force transmission in disordered particle media, and its relation to macroscopic mechanics
Prof. Prabhu Nott, Indian Institute of Science
Granular materials are ubiquitous in nature and industry, but our understanding of their mechanics lags far behind that of fluids. In a densely packed state, granular materials and other athermal particle aggregates transmit stress in a manner that belies their microstructural disorder – a subset of the particle contact network is strikingly coherent, with contacts aligned nearly linearly and transmitting large forces. The origin of these “force chains” has long been a puzzle. In this talk I will attempt to convey the findings of recent studies in my group, where we have used cluster linearity as a network connectivity measure to classify subnetworks of connected contacts. In static particle assemblies and in steady shear, we find a percolation transition at a critical linearity at which the network is sparse, coherent, and contains the force chains. I will show how the subnetwork at critical linearity explains some important experimentally observed features of granular materials, and explains distinctive, even anomalous, features of the stress in granular columns. I will connect these findings to some current questions on constitutive models for granular flow, and the rheology of dense particle-liquid suspensions where stress transmitted by particle contacts play a prominent role.
Monday, November 18, 2019 at 11:00am
Regents Hall, 351
3700 O St. NW