*Condensed Matter & Surface Sciences*

*COLLOQUIUM*

**SARAH
HORMOZI**

Ohio University

*“**Suspensions of Noncolloidal
Particles in Non-Newtonian Fluids: Fluid Mechanics, Rheology and Microstructure**”*

Dense suspensions are materials
consisting of viscous fluids and solid particles with a broad range of sizes. Often, the fine colloidal particles interact
to form a non-Newtonian carrier fluid, which itself transports the coarser
solid noncolloidal particles. These non-
Newtonian slurries can be found in natural settings, such as landslides,
mudslides, and submarine avalanches, and in industrial applications, such as in
tailings from mining operations and fracturing fluids in hydraulic fracturing.
Therefore, there is a compelling need to study the rheological behaviors of Non-Newtonian
slurries to be able to predict their flow dynamics in various practical
situations. However, this prediction is
a challenging problem due to the complex rheology of the Non-Newtonian slurries
and the role of a wide range of elements such as stress inhomogeneity,
sedimentation, inertia, etc.

This talk aims at introducing
our current understanding of the non-Newtonian slurries rheology, particularly
those with yield stress and shear-thinning suspending fluids, and explaining
the complexity when dealing with other types of non-Newtonian suspending fluids
such as thixotropic, viscoelastic and shear-thickening fluids. The main scientific challenge is to establish
a continuum framework for non-Newtonian slurries and refine it through
microstructure investigations. With yield stress viscous suspending fluids,
suspensions may vary on the particle scale from Stokesian behavior to inertial
behavior in a non-homogeneous shear flow. In addition, nonlinearity of the suspending
fluid implies that the suspension kinetics strongly depends on the strain rate.
This talk will also discuss a knowledge
gap and a need for developing experimental and computational techniques to
measure the rheological properties in both Stokesian and inertial regimes. I will present a tensorial continuum framework
based on our recent computational and experimental works. This framework can be used to study dispersion
of solids in industrial processes and geophysical flows. As an example, this model framework will be
used to estimate the streamwise dispersion of particles in recent hydraulic
fracturing techniques. Finally, open
questions will be disclosed which must be answered to build a firm foundation
for a long-term contribution to the area of complex suspensions.

Thursday,
November 9, 2017

4:10
p.m. -- Walter Lecture Hall 245