Condensed Matter & Surface Sciences
“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