Vertical cementing displacement flows of shear-thinning fluids

We present a comprehensive study on the displacement flows of shear-thinning (power-law) fluids in a vertical eccentric annulus, employing both experimental and computational methods. This is a sequel to our previous studies [R. Zhang and I. Frigaard, J. Fluid Mech. 947, A32 (2022); R. Zhang and I. Frigaard, J. Fluid Mech. 972, A38 (2023)], which primarily discussed about the dispersive effects for the displacement flow of two Newtonian fluids. The same set of criteria has been applied to determine a steady/unsteady and dispersive/non-dispersive front. The overall classification map broadly aligns with findings from the Newtonian study, while also offering additional information due to the extreme viscosity ratio present. Our observations reveal that the flow behavior is significantly influenced by both the buoyancy force (b) and the viscosity ratio (M). Specifically, higher values of either b or M tend to induce a more steady and non-dispersive regime. Moreover, we have examined intriguing viscosity effects including viscosity dominant flows and viscous driven instabilities. Shear-thinning effects have also been observed and investigated in this study.