Paper Number
SC32
Session
Suspensions, Colloids, and Granular Materials
Title
The dynamics in and rheology of dilute suspensions of semi-flexible, 2-D colloids
Presentation Date and Time
October 13, 2021 (Wednesday) 5:00
Track / Room
Track 5 / Ballroom 6
Authors
- Swan, James W. (Massachusetts Institute of Technology, Department of Chemical Engineering)
- Silmore, Kevin (MIT)
Author and Affiliation Lines
James W. Swan1 and Kevin Silmore2
1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02142; 2MIT, Cambridge, MA 02474
Speaker / Presenter
Swan, James W.
Keywords
computational methods; colloids; suspensions
Text of Abstract
In this talk, I will discuss simulations of semi-flexible, 2D colloids -- sheets -- in simple shear flow. I will show how sheets deform and flip in this flow field in ways that are well described by Jeffery orbits of very thin oblate spheroids when the sheets are stiff and thermal forces are weak. I will discuss a transition to a a regime of chaotic motion for the sheets when the strength of the flow grows much large. In the chaotic regime, the sheets become crumpled into objects that are more isotropic, and so they more much like spheres through the flow field. Thermal forces have the effect of causing the sheets to flip more often in flow. Because the sheets are two dimensional, they tend to find a stable state in which they become flat in the flow-vorticity plane. Thermal forces perturb this state. We show that the time between thermal events that perturb the sheet from this flat state is well described by the same theories used to explain polymer flipping in solution. Finally, we identify the bounding ellipsoid for the sheets throughout their trajectories in the simple shear flow and use this bounding ellipsoid to estimate the hydrodynamic stresses born by the sheet and from that the viscosity of a dilute solution of sheets in a simple shear flow as a function of shear rate, bending rigidity, and strength of thermal forces.