Collaborative Research: Stability and dispersion of viscoelastic flows through porous media

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Viscoelastic fluids, including polymers and biological materials, exhibit mechanical properties of both fluids and solids. When driven through porous materials, viscoelastic fluids exhibit an abrupt transition to chaotic flow, which is a key feature of enhanced mixing that regulates a vast array of important geological, biological, and industrial processes. Despite our deep understanding of viscoelastic flows in simple model geometries, predicting their flow properties through the intricate, irregular crevices of porous materials remains an outstanding challenge. The goal of this work is to quantify viscoelastic fluid flows in a range of model and realistic porous media and determine how microscopic geometry affects the macroscopic flow and transport properties of viscoelastic fluids. The outcomes of this project will have direct implications for extraction and bioremediation efficiency in rock and soil, minimizing power consumption and cost in polymer processing, and understanding biofilm mechanics that affect soil ecology and infections in humans. Under this project, workshops will be organized to promote early career development of scientists in the field, several undergraduate and graduate students will receive research training, and aspects of this work will be integrated into microfluidics and complex fluids courses.The stability of viscoelastic fluid flows through porous media strongly depends upon the disorder and connectivity of successive pores. The memory of elastic stresses couples advection to pore microstructure making for exquisitely complex stability criteria, and emphasizing the need to consider the Lagrangian character of polymeric flows. A dearth of quantitative studies across relevant two- and three-dimensional flow geometries has yielded often conflicting outcomes and has inhibited our ability to forecast the dispersive transport properties of these systems. To resolve these key deficiencies in our current understanding of viscoelastic flows through porous media, the following principle aims will be achieved through the integration of microfluidic experiments and numerical simulations: (1) Determine the role of geometrical structure, disorder, and porosity on viscoelastic instability in two-dimensional porous media flows. (2) Establish the effect of geometry and viscoelasticity on dispersion in porous media through analysis of Lagrangian coherent structures. (3) Elucidate the role of three-dimensionality in the viscoelastic stability and resultant transport properties of porous media flows. This work will establish a direct link between fluid stress, stretching kinematics, and transport.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.