Suspended Particles in Complex Fluids: From Fracking Fluids to Swimming Worms

Colloquium | October 18 | 4-6 p.m. | 180 Tan Hall

 Eric Shaqfeh, Professor, Stanford University

 Department of Chemical Engineering

Rigid or flexible particles suspended in viscoelastic fluids are ubiquitous in the food industry (e.g. pastes), industrial molding applications (all composites and 3-D printed parts), the energy industry (e.g. fracking fluids), and biological fluids (i.e. swimming of bacteria in mucous). The mathematics of the description of these suspensions is in its infancy. For example, the foundational work in Newtonian suspensions was accomplished by Einstein in 1905 as a mathematical prediction of the shear viscosity of a dilute suspension of particles in Newtonian fluid. That same calculation in an elastic fluid was just submitted for publication now over 100 years later! However, while the mathematics of this subject is subtle the real breakthrough in this area has been the development of a computational simulation of such viscoelastic suspensions, with particle level resolution, such that predictions can be made and tested at all volume fraction loadings. This simulation capability is unique and overcomes the major hurdle in understanding the physics of these suspensions – which in many cases are simply qualitatively different than that of Newtonian suspensions. The simplest flows of such suspensions are not understood at a fundamental level, primarily because the collective behavior of particles in an elastic liquid has no foundation – this will change dramatically in the next few years. I will describe three foundational problems that have now been analyzed using these new computational methods – including fracking fluid design and swimming in an elastic liquid.