Emergent patterns and stable interfaces during radial displacement of a viscoelastic fluid

The displacement of a more viscous fluid by less renders the fluid-fluid interface unstable and leads to intricate patterns called fingers. Since fluids experience shear during displacement, it should be possible influence emergence instability dynamics through control rheological parameters, such as elasticity or relaxation time in case viscoelastic fluid. In this article, we record analyze interfacial fingering that emerge when Newtonian (glycerol-water mixtures different viscosities) displaces shear-thinning (aqueous cornstarch suspensions varying concentrations) radial Hele-Shaw cell geometry. While Newtonian-non-Newtonian pair displacements have drawn attention researchers past, current work showcases various regimes emergent over wide range viscosity ratios two fluids, effect on rate its displacement. As ratio viscosities inner outer is increased, branched are replaced stable interfaces display finger coalescence. Increasing displacing concentration-dependent both lead significant suppression instabilities. A linear stability analysis interface, using only parameter, employed predict dominant wavelength perturbation. perturbation computed numerically found match closely with spacing between fingers measured experimentally at onset instability. It suggested instabilities miscible (mud slurries, for example) has implications material processing, ensuring minimal mixing phases while maximizing sweep efficiency recovery.