Effects of Shear-Thickening Characteristics of Silica-Polyethylene Glycol on Immiscible Newtonian-NonNewtonian Fluids Interfacial Dynamics in Radial Displacement Inside the Hele-Shaw Cell

This study experimentally investigates the phenomenon of viscous fingering during the radial displacement of immiscible fluids within a Hele-Shaw cell, focusing on the interaction between a Newtonian and a shear-thickening fluid. Specifically, liquid paraffin, serving as the Newtonian fluid, is injected to displace a suspension of silica in polyethylene glycol ۴۰۰, which exhibits shear-thickening behavior. Silica-PEG suspensions were used with a weight concentration of ۱۰, ۱۵, and ۲۰% silica. Rheological analyses revealed that the shear-thickening behavior of silica-PEG suspensions becomes more pronounced with increasing silica concentration. The experimental results further demonstrated that shear-thickening effects manifest at the early stages of finger formation (t ≲ ۱, t* ≲ ۵۴۰۰). Additionally, the fingertips positioned at varying radial distances are subjected to non-uniform shear rates. Similar to the Newtonian systems, increasing the injection flow rate led to an increase in interfacial instability. It was also concluded that the existence of shear-thickening characteristics was amplified by increasing the flow rate. Moreover, the interfacial instability in Newtonian-shear-thickening displacement increased ۲۵% than that of the Newtonian fluid's displacement (number of fingers increased from ۱۵ to ۲۵). Also, effective fingertips length was ۱۱% longer for the Newtonian-shear-thickening system (it increased from ۶.۵ to ۷.۲). Besides, increasing the concentration of silica-PEG suspension leads to an increase in viscosity (۴.۶ Pa. s to ۱۳.۶ Pa. s), a reduction in interfacial tension (۴۸ mN/m to ۱۶ mN/m), and an increase in the injection capillary number (۰.۰۸ to ۰.۲۶). This was the main reason that Shear-thinning features displayed by silica-PEG suspension resulted in an increase in interfacial instability and made narrower fingers for the displacement of ۲۰ wt.% silica-PEG. Notably, these findings contrast with previously reported data in the literature. However, by comparing the maximum number of fingers observed at the conclusion of the injection process with existing studies, and selecting the coefficient D, an excellent agreement is achieved between Paterson’s theoretical predictions and the present experimental results.

کلیدواژه ها:

Immiscible radial displacement ، Interfacial instability ، Hele-Shaw cell ، Shear-thickening ، Silica-polyethylene glycol ۴۰۰