Permeation of high concentration polymer fluids in porous micromodels*

We present an experimental model of the flow of high molecular weight polymer fluids from an open cavity into a porous medium. Our micromodels consist of microfluidic devices that recapitulate porous geometries and interfaces at a range of scales. As a model fluid, we study partially hydrolyzed polyacrylamide (HPAM) solutions. Using a custom microscopy setup and a variety of imaging methods, including machine learning-assisted particle tracking velocimetry, we explore both three-dimensional pore-scale flow and two-dimensional network-scale flow. In previous work, HPAM solutions have been widely employed in porous micromodels due to their well characterized shear thinning rheology, which holds relevance to many practical applications. Motivated by the specific role of these solutions as support fluids in civil engineering projects, we investigate higher concentrations than have typically been explored (beyond the critical overlap concentration) and the influence of solid colloidal contaminants, which capture typical site conditions that have previously been overlooked in laboratory experiments.