Speaker
Description
In civil engineering, it is common practice to support the walls of an open excavation, such as a borehole or trench, by filling it with fluid. The traditional and most widely used support fluids are slurries of bentonite clay in water. Semi-dilute aqueous solutions of high-molecular-weight polymer ("polymer fluids") are known to have a variety of advantages over traditional bentonite slurries, in terms of both cost and environmental impact, but they remain under-used because they are poorly understood. Here, we study the permeation of polymer fluids through porous micromodels to develop qualitative and quantitative insight into their flow through the pore space and their interactions with the solid skeleton. Our micromodels consist of custom microfluidic devices across a range of complexities. We image these flows via a custom microscopy setup and then use machine-learning-assisted particle-tracking velocimetry to explore transient 3D flow fields at the pore scale. Our working fluid is a semidilute aqueous solution of partially hydrolyzed polyacrylamide (HPAM). We focus on the link between the viscoelastic transients that occur in simple shear rheometrey and the anomalously large pressure drops that occur in both simple and complex micromodels. We propose a simple toy model for the effective rheology of these viscoelatic, shear-thinning fluids and explore its implications for the radially outward permeation of polymer fluid from a borehole into the surrounding water-saturated soil.
| Country | United Kingdom |
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