Viscous fingering to fracturing transition in Hele–Shaw flow of shear-thickening fluid

Abstract

We experimentally investigate the interplay of viscous fingering and fracturing in a radial Hele–Shaw cell displacing a non-Newtonian (shear-thickening) fluid. We have used cornstarch suspension of different compositions (39%–48% w/w dispersed in water–CsCl solution), and the rheology of the suspension exhibits shear thickening behavior beyond a shear rate of 1 s−1. We observe the transition from viscous fingering to dendritic fracturing morphology beyond a critical weight fraction of cornstarch suspension. We analyze the plot of the fraction of injected phase to displaced phase as a function of injected volume for different weight fractions of cornstarch suspension. The injection pressure of the invading fluid (air or oil) used in the present work has no significant effect on the transition from viscous fingering and fracturing patterns. The transition of the pattern is possible if the injection pressure (and consequently the flow rate) is increased. The width of the finger decreases with the injection pressure of the invading fluid and widens with the injected volume due to the reduced local shear rate beyond a critical size. The width of the dendritic fracturing decreases with the injection pressure of invading fluid but increases with the injected volume.

Interfacial instabilities in confined displacements involving non-Newtonian fluids

“…4(b)) were produced [72]. A transition from VF to VEF was reported in cornstarch suspensions when oil was used as a displacing fluid [74]. Miscible displacements of discontinuously shear-thickening cornstarch suspensions with water [73] showed transient invasion of air into the suspension and formation of reverse fingers at the outermost interface between the suspension and atmospheric air (fig.…”

“…Shear-thickening fluids display continuous shearthickening (CST), discontinuous shear-thickening (DST), and shear-jamming (SJ) flow regimes with increasing particle volume fraction φ and applied shear stress σ/rate γ [6]. These distinct rheological regimes of cornstarch suspensions can be achieved in radial displacement experiments by appropriately controlling the injection pressures of the displacing Newtonian fluids [72][73][74]. When cornstarch suspensions in CST, DST and SJ were displaced by immiscible air in separate experiments, three distinct interfacial patterns, viz., viscous fingering (VF), dendritic fracturing (DFr) and system-wide fracturing (Fr) (fig.…”