(4ll) Viscoelastic Flow Instabilities in Porous Media

Viscoelastic fluid flows in porous media are ubiquitous in environmental and industrial applications, from groundwater remediation to filtration processes and chemical production. The addition of chemical additives such as polymers or surfactants—even in dilute amounts– can impart a fluid with substantial elasticity. As fluid navigates through the tortuous pore space, strong flow gradients and curved flow paths can generate substantial elastic stresses and give rise to an elastic flow instability characterized by chaotic spatiotemporal flow fluctuations: flow patterns reminiscent of inertial turbulence but occur at extremely low Reynolds numbers (). As the transport of heat, mass, and momentum are typically diffusion-limited in the low operating conditions characteristic of many porous media flow applications, the chaotic dynamics arising from elastic flow instabilities show exciting potential towards enhancing transport of solutes, particles, and heat within porous media.

Research Interests: My PhD research focuses on understanding how pore space geometry and fluid rheology influences the onset and features of elastic flow instabilities, leveraging insight from pore-scale flow field. I have found that the pore geometry plays an important role in features of elastic instabilities, where changes in grain packing type, disorder and order, and 2-D and 3-D can drastically influence local flow features and the onset of instability—even for the same fluid. Conversely, fluid rheology can additionally alter flow instability behavior within the same porous medium geometry; I have found that by accounting for the fluid rheology using a Deborah number, we can predict certain elastic instability features for flow in a 1-D porous medium.

At the macroscopic scale, the flow of polymer solution in porous media can exhibit anomalous “flow thickening”— a drastic increase in flow resistance—above a threshold flow rate in porous media. The precise mechanisms generating this flow thickening have remained a puzzle since the first reports in the 1960s. By leveraging access to in situ pore-scale flow fields, I have directly quantified the contributions of different mechanisms contributing to the increased flow resistance: unstable viscous dissipation arising from an elastic instability coupled with added resistance from the polymeric extensional viscosity, finding that the contributions of each resistance are strongly mediated by pore geometry.

Guided by these results, I have developed an experimental platform to assess the potential of leveraging elastic instabilities for remediating contaminated soiled porous media. Under matched flow rate conditions, we find that polymer solution injection—above a threshold flow rate—achieves greater removal efficacy compared to an equivalent flow of a viscous Newtonian solvent. We hypothesize that the enhanced removal efficacy results from flow fluctuations arising from the instability and the increased extensional stresses associated with the fluid viscoelasticity. This work provides important insight into the in situ removal dynamics of microplastics in geometrically-complex environments and highlights the exciting potential of viscoelastic fluid flows towards the remediation of contaminated porous media.

Teaching Interests: As a teaching assistant for an introduction to soft matter class, I developed interactive demonstrations that allowed students to interact with course material, helping them to bring concepts from lecture into a physical, hands-on learning experience. I have also volunteered at several engineering science outreach events for the community, through which I have learned how to communicate science to a broader audience. Through mentorship of undergraduate students in lab, I have been able to teach not only scientific concepts and the research process, but I also have provided professional development guidance towards interviewing, presentations and effective communication, and preparation of applications. From these teaching and mentorship experiences, I hope to bring a personalized, student engagement-centered approach to learning in the classroom with an additional focus to development of soft skills and professional development to help students grow beyond the classroom.