Particle dispersion in porous media: Differentiating effects of geometry and fluid rheology

Abstract

We investigate the effects of geometric order and fluid rheology on the dispersion of micron-sized particles in two-dimensional microfluidic porous media. Particles suspended in a mixture of glycerol and water or in solutions of partially hydrolyzed polyacrylamide (HPAM) polymers were imaged as they flowed through arrays of microscale posts. From the trajectories of the particles, we calculated the velocity distributions and thereafter obtained the longitudinal and transverse dispersion coefficients. Particles flowed in the shear-thinning HPAM solution through periodic arrays of microposts were more likely to switch between streamlines, due to elastic instabilities. As a result, the distributions of particle velocity were broader in HPAM solutions than in glycerol-water mixtures for ordered geometries. In a disordered array of microposts, however, there was little difference between the velocity distributions obtained in glycerol-water and in HPAM solutions. Correspondingly, particles flowed through ordered post arrays in HPAM solutions exhibited enhanced transverse dispersion. This result suggests that periodic geometric order amplifies the effects of the elasticity-induced velocity fluctuations, whereas geometric disorder of barriers effectively averages out the fluctuations.

Convective dissolution of carbon dioxide in two- and three-dimensional porous media: The impact of hydrodynamic dispersion

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“…All these studies discussed particle migration in periodic arrays of pillars in Newtonian fluids and there are even fewer studies that study particle migration with non-Newtonian fluids. [16][17][18] Jacob et al 17 investigated the particle dispersion of 2 mm particles in a Newtonian and shear-thinning elastic fluid (HPAM) and they presented an analysis of the influence of elastic instabilities. However, due to the presence of both elasticity and shearthinning properties in HPAM, the effect of each property could not be studied separately.…”