title: Discontinuous shear thickening in Brownian suspensions by dynamic simulation.
abstract: Dynamic particle-scale numerical simulations are used to show that the shear thickening observed in dense colloidal, or Brownian, suspensions is of a similar nature to that observed in noncolloidal suspensions, i.e., a stress-induced transition from a flow of lubricated near-contacting particles to a flow of a frictionally contacting network of particles. Abrupt (or discontinuous) shear thickening is found to be a geometric rather than hydrodynamic phenomenon; it stems from the strong sensitivity of the jamming volume fraction to the nature of contact forces between suspended particles. The thickening obtained in a colloidal suspension of purely hard frictional spheres is qualitatively similar to experimental observations. However, the agreement cannot be made quantitative with only hydrodynamics, frictional contacts, and Brownian forces. Therefore, the role of a short-range repulsive potential mimicking the stabilization of actual suspensions on the thickening is studied. The effects of Brownian and repulsive forces on the onset stress can be combined in an additive manner. The simulations including Brownian and stabilizing forces show excellent agreement with experimental data for the viscosity η and the second normal stress difference N2.
authors.affiliation: Benjamin Levich Institute, The City College of New York, New York, NY 10031; rmari@damtp.cam.ac.uk.
authors.forename: Romain
authors.initials: R
authors.lastname: Mari
authors.affiliation: Benjamin Levich Institute, The City College of New York, New York, NY 10031; Mathematical Soft Matter Unit, Okinawa Institute of Science and Technology, Okinawa, 904-0495, Japan;
authors.forename: Ryohei
authors.initials: R
authors.lastname: Seto
authors.affiliation: Benjamin Levich Institute, The City College of New York, New York, NY 10031; Department of Chemical Engineering, The City College of New York, New York, NY 10031.
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Morris
authors.affiliation: Benjamin Levich Institute, The City College of New York, New York, NY 10031; Department of Chemical Engineering, The City College of New York, New York, NY 10031.
authors.forename: Morton M
authors.initials: MM
authors.lastname: Denn
keywords: colloidal suspensions; jamming; rheology; shear thickening; soft matter