Contact forces in viscous suspensions: Discontinuous shear thickening and shear jamming

Time: Wednesday, April 11, 2018 - 2:30pm - 3:30pm
Type: Seminar Series
Presenter: Jeff Morris; Levich Institute and Department of Chemical Engineering, The City College of New York
Room/Office: Room 107
Location:
Mason Lab
9 Hillhouse Avenue
New Haven, CT 06511
United States

Department of Mechanical Engineering & Materials Science Seminar

Jeff Morris
Levich Institute and Department of Chemical Engineering
The City College of New York

"Contact forces in viscous suspensions: Discontinuous shear thickening and shear jamming"

Large changes in properties can be disruptive in engineering of flow processes. On the other hand, such changes may be tailored to be useful. One case which shows these features is described here. We consider the extreme changes in properties with increase of imposed shear rate (or stress) in highly concentrated ("dense") suspensions of solid particles in viscous liquids. The central phenomenon is abrupt or "discontinuous" shear thickening (DST), in which the apparent viscosity increases by orders of magnitude at a critical shear rate for suspensions approaching their maximum flowable solid fraction. For many years, DST has been known, and popular videos of running on "oobleck" (cornstarch suspended in water) are found on-line. Yet the fundamental basis has been controversial for reasons that will be outlined. This talk will review a simulation method based on a minimal model—including viscous, electrostatic repulsion and contact frictional interactions between particles—that reproduces DST. Comparisons of simulation predictions to experimental data for several cases, including colloidal Brownian (submicron size) [1] as well as larger-particle suspensions [2], will be made.

The constitutive behavior of these dense suspensions in shear flow, based on a phenomenological model [3,4] in which the crucial assumption is the transition from viscous-to-frictional interactions between particles, will be described and shown to be very successful. The overall behavior, captured in a flow state diagram depending on the applied shear stress and the solid volume fraction, suggests a close relationship between shear thickening, frictional-particle shear jamming (SJ), and the jamming of frictionless particles under isotropic loading. Both DST and SJ require contact networks between particles to develop in this scenario, and recent findings will be presented on the topological properties of these networks based on analysis of extensive statistical sampling from simulations. This allows study of the microstructural force organization forming the basis of the phenomenological theory for the predicted flow property transitions.

1. R. Mari, R. Seto, J. F. Morris & M. M. Denn 2015 Proc. Nat. Acad. Sci. 112, 15326.
2. R. Seto, R. Mari, J. F. Morris & M. M. Denn 2013 Phys. Rev. Lett. 111, 218301.
3. M. Wyart & M. E. Cates 2014 Phys. Rev. Lett. 112, 098302.
4. A. Singh, R. Mari, M. M. Denn & J. F. Morris 2018 J. Rheol. 62, 457.

Wednesday, April 11, 2018
2:30 – 3:30 pm
Location – Mason 107

Host: Professors Alessandro Gomez & Corey O'Hern
Refreshments served at 2:15 pm