Jason E. Butler
Ph.D., 1998, The University of Texas at Austin
Ph : 352-392-2591
Fx: 352-392-9513
431 Chemical Engineering Building
Dynamics of Complex Fluids
Suspension and Multiphase Fluid Mechanics
Polymer Dynamics
Microfluidic Flows of Complex Materials
My research group studies dynamic phenomena within complex fluids using experimental, computational, and theoretical tools. Complex fluids, encompassing suspensions of particulates, emulsions, and polymeric solutions and melts, serve important roles in biotechnology, nanotechnology, materials science, and emerging industrial technologies. Efficient control and processing of these materials requires an understanding of their transport properties, yet complex fluids often demonstrate unexpected and intriguing behavior under flow. Some specific examples from our studies are described.
Migration of macromolecules within microfluidic devices

Keywords: Complex Fluids, Transport phenomena, Biomolecular/Biomedical

Macromolecules flowing within a confined geometry experience hydrodynamic and thermodynamic forces that can cause conformational changes and net migration of the molecules. Recent simulations and theoretical calculations demonstrated that the direction and extent of migration depends upon multiple factors, which can have important implications for the transport and control of polymers in microfluidic devices. We are exploring possibilities for using the phenomena for separations and other applications.
Dynamics and rheology of nanorods and rigid polymers

Keywords: Complex Fluids, Transport phenomena, Nanosciences

Rigid polymers are widely used as high performance plastics and examples of Brownian fibers can be found in the form of macromolecules of biological origin and in nanotechnology in the form of nanotubes and nanorods. Current work focuses on eliminating the disparity between quantitative predictions and measurements of the dynamic and rheological properties of suspensions of Brownian rods and rigid polymers. This includes resolving the scaling for the the long-time rotational diffusion in semi-dilute suspensions and elucidating the mechanism for shear thinning in suspensions in the limit of strong shear and weak diffusion.
Structure and rheology in oscillating suspensions
Keywords: Complex Fluids, Transport phenomena
Suspensions of non-colloidal spheres in non-uniform flows can demix due to hydrodynamic interactions. For oscillatory flows of suspensions within a tube, experiments indicate that the particles migrate toward the wall under some conditions and that there is sometimes a segregation of particles along the pipe axis. We have explored the origin of this unexpected behavior using rheological and simulations studies. Previously unidentified phenomena resulting from the experiments and modeling efforts have included the irreversibility of the suspensions (as reflected by long-time changes in the rheology) even at small amplitudes of oscillation and non-monotonic viscosities which arise from underlying phase changes in the microstructure.
Instabilities in sedimentation of non-spherical particles
Keywords: Complex Fluids, Transport phenomena
Mutual hydrodynamic interactions among rigid rods sedimenting in a viscous fluid create inhomogeneities in concentration which, in turn, can enhance the mean sedimentation rate beyond that measured in a dilute suspension. This contrasts with sedimenting spheres, where increasing concentration hinders the sedimentation rate. Continuing work focuses on measuring the instability, refining the models, and extending the concept to other particle types. Improved models will aid design of separation processes and understanding of natural sedimentation processes.
Research_Image Rigid rods sedimenting in a viscous fluid
Recent Publications
1. Hyun-Ok Park, Jonathan M. Bricker, Michael J. Roy, and Jason E. Butler, “Rheology of oscillating suspensions of non-colloidal spheres at small and large accumulated strains,” Physics of Fluids, 23,013301, 2011.
2. Rahul Kekre, Jason E. Butler, and Anthony J.C. Ladd, “The role of hydrodynamic interactions in the migration of polyelectrolytes driven by a pressure gradient and an electric field,” Physical Review E, 82, 050803(R), 2010.
3. Bloen Metzger and Jason E. Butler, “Irreversibility and chaos: Role of long-range hydrodynamic interactions in sheared suspensions,” Physical Review E, 82, 051406, 2010.
4. Joontaek Park and Jason E. Butler, “Theoretical analysis of rigid polymers and nanorods in a rotating viscometric flow,” Macromolecules, 43, 2535-2543, 2010.
5. Joontaek Park and Jason E. Butler, “Inhomogeneous distribution of a rigid fibre undergoing rectilinear flow between parallel walls at high Peclet numbers,” Journal of Fluid Mechanics, 630, 267-298, 2009.